United States 

Department of 

Agriculture

Animal and 

Plant Health 

Inspection 

Service

Veterinary 

Services

National 

Animal Health 

Monitoring 

System

September 

2013

Sheep 2011

Part III: Health and Management Practices on 

U.S. Sheep Operations, 2011
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USDA–APHIS–VS–CEAH–NAHMS

NRRC Building B, M.S. 2E7

2150 Centre Avenue

Fort Collins, CO 80526–8117

970.494.7000

http://nahms.aphis.usda.gov

#632.0913

Cover photograph courtesy of American Sheep Industry Association
USDA APHIS VS / i 

Flock additions

Producers sometimes inadvertently bring disease onto their operations by adding new 

animals to their fl ock. About one-third of U.S. sheep producers minimized their risk of 

acquiring new disease in their fl ock by not adding new animals, other than by natural 

birth. The longer an operation goes without adding animals, the higher the certainty that 

no asymptomatic, but infected, animals exist in the fl ock. Operations that did not add 

sheep during 2010 were considered “closed” fl ocks. On average, rams had not been 

added to closed fl ocks for 3.7 years, while ewes and lambs had not been added to closed 

fl ocks for 9.0 and 8.4 years, respectively. 

Reproduction management

An accurate annual estimate of the actual lamb crop is an important measurement of 

fl ock productivity. Nearly all operations can provide their lambing rate, but it is not always 

clear how the rate is measured. For some operations in the largest lamb producing 

States (especially range fl ocks), the predocking period is an enigma. Therefore, their 

lambing rate is based on the number of lambs docked divided by the number of ewes 

bred. This method has its limitations. For these operations, the entire period from lambing 

to docking cannot be examined to determine whether the majority of lambs are lost to 

predators, a lack of colostrum, poor mothering, scours, pneumonia, or other causes. 

Losses are diffi cult to prevent if the cause of loss remains unknown. 

Nearly half of all operations (47.3 percent) calculated the lambing rate by determining the 

number of lambs born divided by ewes bred. Over half of large operations 

(54.9 percent) determined lambing rate by estimating the number of lambs docked 

divided by the number of ewes bred. The producer-expected lambing percentage overall 

was 1.50. Small and medium operations had a higher expected lambing rate (1.53 and 

1.47, respectively) than large operations (1.23).

Controlled internal drug release (CIDR) devices were approved for use in the United 

States in 2009. Overall, 6.7 percent of operations used CIDRs in 2010, and 95.6 percent 

of these operations would use them again. Three-fourths of operations that used CIDRs 

used them for out-of-season breeding.

Placentas can harbor infectious organisms and should be removed as soon after lambing 

as possible. Removing placentas is especially important on high-density operations in 

which ewes are clustered and exposure to placental organisms is high. In general, 

67.9 percent of operations usually removed placentas from the lambing area. Composting 

and throwing out for carnivores were the two most common methods for disposing of 

placentas (30.8 and 28.0 percent of operations that removed placentas, respectively). 

Items of Note
ii / Sheep 2011

Diseases and control methods

Nearly all operations (92.0 percent) had an APHIS-assigned fl ock identifi cation number. 

Overall, producers on 84.8 percent of operations were either very or somewhat familiar 

with scrapie. Of these, about half (47.3 percent) implemented genetic selection for 

scrapie control, and of these almost all (98.8 percent) used replacement rams genetically 

less susceptible (RR alleles) to scrapie. 

Toxoplasmosis and coxiellosis (Q fever) are common causes of abortion storms in 

sheep fl ocks, yet producers on 28.5 and 52.0 percent of operations had not heard of 

toxoplasmosis and Q fever, respectively. 

Vaccines can reduce the prevalence or severity of disease and are an integral part of any 

fl ock management program. Overall, 81.6 percent of operations used vaccines in 2010. 

The highest percentage of operations vaccinated against enterotoxemia and tetanus 

(71.4 and 64.5 percent of operations, respectively). A higher percentage of herded/open 

range fl ocks vaccinated for sore mouth compared with other fl ock types. Because the 

sore mouth vaccine is comprised of live virus, vaccinating against sore mouth is only 

recommended when a fl ock is already infected with the virus. The highest percentage of 

operations that vaccinated for sore mouth (70.6 percent) used a commercially available 

sore mouth vaccine. 

Antibiotic use

Record keeping is an essential part of responsible antibiotic use. Records should 

include the name of the antibiotic used, animals treated, date treated, and reason(s) 

for treatment. During 2010, 69.0 percent of operations administered oral, injectable, or 

topical antibiotics to lambs or ewes to treat any disease. Just over half of operations that 

administered antibiotics (51.0 percent) kept antibiotic-usage records. The most commonly 

treated illness on sheep operations was respiratory disease; for operations that gave 

any antibiotics, 67.7 percent treated sheep for this illness during 2010. The antibiotic 

class used most frequently to treat respiratory disease was penicillin (29.9 percent of 

operations), followed by tetracycline (19.2 percent) and fl orfenicol (13.6 percent).
USDA APHIS VS / iii 

Terms Used in This Report 3

Section I: Population Estimates 5

A. General Management 5

1. Ewe age 5

2. Flock additions 6

3. Operations with no fl ock additions in 2010 8

4. Contact with other animals 10

5. Rodent control 12

6. Visitors 13

7. Housing 18

8. Manure handling 21

9. Offi cial fl ock identifi cation and ear tags 23

10. Identifi cation other than offi cial scrapie program ear tags 26

B. Reproduction Management 28

1. Calculation of lambing rate 28

2. Normal or average lambing rate 31

3. Lambing season 34

4. Breeding management for the last completed lambing season 35

5. Lambing outcome 37

6. Low lambing rate 40

7. Lamb supplements 47

8. Ewe synchronization 52

C. Lambing Management 55

1. Manure and waste bedding management during lambing 55

2. Placenta removal and disposal 58

3. Abortion 61

4. Tail docking 67

D. Disease Control and Illness 69

1. Health management 69

2. Johne’s disease 76

3. Scrapie 78

4. Ovine progressive pneumonia 80

5. Toxoplasmosis and coxiellosis 83

6. Diseases present in the last 3 years 84

7. Vaccination practices 85

8. Market lamb injections 92

Table of Contents
iv / Sheep 2011

E. Antibiotics 97

1. Antibiotic use 97

2. Antibiotic treatment records 99

3. Antibiotics given 101

4. Treatment of nursing lambs 104

5. Treatment of weaned replacement lambs 107

6. Treatment of weaned market lambs 110

7. Treatment of ewes 113

8. Coccidiostats and growth promotants 117

F. Parasites and Deworming 121

1. Fecal testing 121

2. Deworming 122

3. Dewormer effi cacy and information sources 129

4. Fly, ked, and tick control 133

G. Pasture Management, Water Sources, and Feeding Practices 136

1. Pasture management 136

2. Water sources 139

3. Feeding practices 141

Section II: Methodology 143

A. Needs Assessment 143

B. Sampling and Estimation 144

1. State selection 144

 2. Operations selection 145

3. Population inferences 145

C. Data Collection 146

1. Data collectors and data collection period 146

D. Data Analysis 146

1. Phase I: Validation—General Sheep Management Questionnaire 146

2. Phase II: Validation—VS Visit Questionnaires 146

E. Sample Evaluation 147

1. Phase Ia: General Sheep Management Questionnaire—

fewer than 20 ewes 147

2. Phase Ib: General Sheep Management Questionnaire—

20 or more ewes 148

3. Phase II: VS Initial Visit Questionnaire 149
USDA APHIS VS / v 

Appendix I: Sample Profi le 150

Appendix II: U.S. Ewes Population and Farms 151

A. Number of Ewes–State, Region, and United States 151

B. Ewes, Flock Size Distribution–State, Region, and United States 152

C. U.S. Sheep and Lamb Population, January 1, 2011, Inventory 153

D. Breeding Sheep: Survey Percent by Size Group, United States, 

2008–09 154

Appendix III: Antibiotic Classes and Active Ingredients 155

Appendix IV: Study Objectives and Related Outputs 156
vi / Sheep 2011

This report was a cooperative effort between two U.S. Department of Agriculture (USDA) 

Agencies: the National Agricultural Statistics Service (NASS) and the Animal and Plant 

Health Inspection Service (APHIS). 

We’d like to thank the NASS enumerators who contacted sheep producers and collected 

the data. Their hard work and dedication were invaluable. Recognition also goes to 

personnel at the USDA–APHIS–Veterinary Services and individual State Departments of 

Agriculture for their efforts in collecting data and generating and distributing this report.

Additional biological sampling and testing for the Sheep 2011 study were afforded by the 

generous contributions of collaborators, including:

 DHHS–CDC, NCEZID, Poxvirus Branch

 IDEXX Laboratories, Inc., Westbrook, ME

 Iowa State University, College of Veterinary Medicine

 University of Georgia, College of Veterinary Medicine

 USDA–APHIS–VS National Veterinary Services Laboratories, Ames, IA

 USDA–ARS, Animal Parasitic Disease Laboratory, Beltsville, MD

 USDA–ARS, Bacterial Epidemiology and Antimicrobial Resistance Research 

Unit, Athens, GA

 USDA–ARS, Pullman, WA

 Washington State University, College of Veterinary Medicine

All participants are to be commended, particularly the producers whose voluntary efforts 

made the Sheep 2011 study possible.

Larry M. Granger 

Director

Centers for Epidemiology and Animal Health

Acknowledgements
USDA APHIS VS / vii 

Suggested bibliographic citation for this report:

USDA. 2013. Sheep 2011, “Part III: Health and Management Practices on U.S. Sheep 

Operations, 2011”

USDA–APHIS–VS–CEAH–NAHMS. Fort Collins, CO

#629.0913

Contacts for further information:

Questions or comments on data analysis: Dr. Katherine Marshall (970) 494–7000

Information on reprints or other reports: Ms. Abby Zehr (970) 494–7000

Feedback

Feedback, comments, and suggestions regarding Sheep 2011 study reports are 

welcomed. You may submit feedback via online survey at: http://nahms.aphis.usda.gov 

(Click on “FEEDBACK on NAHMS reports.”)
USDA APHIS VS / 1 

Introduction

The National Animal Health Monitoring System (NAHMS) is a nonregulatory program of 

the United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection 

Service (APHIS). NAHMS is designed to help meet the Nation’s animal-health information 

needs and has collected data on sheep health and management practices through two 

previous studies. 

The NAHMS 1996 National Sheep Survey was developed through collaboration with the 

Research and Education Division of the American Sheep Industry Association (ASI) and 

focused on identifying health and productivity issues affecting America’s sheep industry. 

Study results provided an overview of sheep health, productivity, and management on 

5,174 U.S. sheep operations. 

The NAHMS Sheep 2001 study was designed to provide both participants and the 

industry with information about the U.S. sheep fl ock on operations with one or more 

sheep. The USDA’s National Agricultural Statistics Service (NASS) collaborated with 

APHIS’ Veterinary Services (VS) to select a producer sample statistically designed to 

provide inferences to the Nation’s sheep population in 22 participating States. These 

22 States accounted for 87.4 percent of the U.S. sheep inventory on January 1, 2001, 

and 72.3 percent of U.S. sheep operations in 2000. 

The NAHMS Sheep 2011 study was conducted in 22 of the Nation’s major sheepproducing States (see map). The study provides participants, stakeholders, and the 

industry with valuable information representing 70.1 percent of U.S. farms with ewes and 

85.5 percent of the U.S. ewe inventory (NASS 2007 Census of Agriculture). 

“Part III: Health and Management Practices on U.S. Sheep Operations, 2011” is the third 

report containing national information from the NAHMS Sheep 2011 study. Data for this 

report were collected from 1,241 operations with 20 or more ewes. Representatives of 

these operations were personally interviewed by either Federal or State animal health 

offi cials from March 14 to June 30, 2011.

The methods used and number of respondents in the study can be found in section II and 

appendix I, respectively.

Introduction
2 / Sheep 2011

Introduction

Sheep 2011 Participating States 

Regions

Central 

West

East 
USDA APHIS VS / 3 

Introduction

Coxiellosis: A bacterial infection in sheep and other animals caused by Coxiella burnetii.

Also known as Q fever in humans.

Ewe: A female sheep 1 year old or older. 

Flock size: Flock sizes are based on the number of ewes for each operation on the 

NASS list sampling frame on January 1, 2011. Size breakouts are: small (20–99); 

medium (100–499); large (500 or more) [section II.B, p 144].

Flock type: The following fl ock types represent only fl ocks with 20 or more ewes. The 

majority of operations had more than one fl ock type.

Herded/open range: Any unfenced acreage, even if it was a few acres surrounded by 

residential areas.

Fenced range: Any fenced area not specifi cally cultivated to raise forage or browse.

Pasture: Any fenced area specifi cally cultivated to raise forage or browse.

Dry lot/feedlot: This study enrolled only operations with ewes. It does not include any 

typical sheep feedlot operations and is not meant to represent the sheep feedlot 

industry. Rather, the dry lot/feedlot category represents operations that fed ewes 

in dry lots or in “feedlot situations.” In many ways, these operations managed, fed, 

and marketed their sheep and lambs similarly to the other fl ock types. Over twothirds of these operations also kept their sheep on fenced range or pasture.

Lamb: Sheep less than 1 year old.

Operation average: A single value for each operation is summed over all operations 

reporting and divided by number of operations reporting.

Population estimates: Estimates in this report are provided with a measure of precision 

called the standard error. A 95-percent confi dence interval can be created with bounds 

equal to the estimate plus or minus two standard errors. If the only error is sampling 

error, the confi dence intervals created in this manner will contain the true population 

mean 95 out of 100 times. For example, an estimate of 7.5 with a standard error of 1.0 

results in limits of 5.5 to 9.5 (two times the standard error above and below the estimate). 

If rounded to 0, the standard error was reported (0.0). If there were no reports of the 

event, no standard error was reported (—). Column totals are shown as 100.0 to aid in 

interpretation. However, estimates may not sum to 100.0 due to rounding.

Terms Used in 

This Report
4 / Sheep 2011

Introduction

Regions:

West: California, Oregon, Washington

Central: Colorado, Idaho, Kansas, Montana, New Mexico, South Dakota, Texas, Utah, 

Wyoming

East: Iowa, Kentucky, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, 

Virginia, Wisconsin

Sheep: Animal 1 year old and older.

Tail docking: The removal of lambs’ tails, usually to prevent accumulation of manure 

around the hindquarters. 
USDA APHIS VS / 5 

Section I: Population Estimates–A. General Management

Note: Column totals are shown as 100.0 to aid in interpretation. However, estimates may 

not sum to 100.0 due to rounding.

1. Ewe age 

Just under one-fourth of ewes were between the ages of 1 and 2 years.

A.1.a. Percentage of ewes by age of ewes during 2010, and by fl ock size:

Percent Ewes

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Age (years) Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

1– <2 27.8 (1.1) 22.6 (0.9) 23.0 (1.5) 23.8 (0.9)

2 or more 72.2 (1.1) 77.4 (0.9) 77.0 (1.5) 76.2 (0.9)

Total 100.0 100.0 100.0 100.0

A higher percentage of ewes on herded/open range operations (80.0 percent) were 

2 years old or older compared with ewes on pasture operations (74.3 percent).

A.1.b. Percentage of ewes by age of ewes during 2010, and by primary fl ock type:

Percent Ewes

Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Age (years) Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

1– <2 20.0 (1.3) 24.9 (2.2) 25.7 (0.9) 24.6 (1.8)

2 or more 80.0 (1.3) 75.1 (2.2) 74.3 (0.9) 75.4 (1.8)

Total 100.0 100.0 100.0 100.0

Section I: Population Estimates

A. General 

Management
6 / Sheep 2011

Section I: Population Estimates–A. General Management

2. Flock additions

During 2010, 67.0 percent of operations added sheep or lambs in addition to those added 

naturally through births. Of these operations, the highest percentage (44.6 percent) 

added rams 1 year old or older. A lower percentage of small operations than large 

operations added new sheep of any kind (63.2 and 78.9 percent, respectively). 

A.2.a. Percentage of operations that added sheep and lambs during 2010, by type of 

sheep added, and by fl ock size: 

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Ewes 1 year 

and older 25.4 (2.5) 29.3 (3.1) 27.9 (4.6) 26.5 (1.9)

Rams 1 year 

and older 38.3 (2.8) 56.1 (3.4) 70.3 (5.0) 44.6 (2.1)

Lambs less than 

1 year old of either 

gender

29.2 (2.6) 28.9 (3.1) 31.7 (4.5) 29.3 (2.0)

Any 63.2 (2.8) 74.7 (2.7) 78.9 (4.9) 67.0 (2.1)

A.2.b. Percentage of operations that added sheep and lambs during 2010, by type of 

sheep added, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot 

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Ewes 1 year 

and older 28.1 (7.4) 30.6 (4.5) 23.2 (2.3) 39.8 (6.8)

Rams 1 year 

and older 66.5 (9.4) 46.8 (4.7) 42.8 (2.6) 43.9 (7.0)

Lambs less than 

1 year old of either 

gender

16.3 (4.1) 26.7 (4.2) 29.3 (2.5) 36.4 (6.4)

Any 77.6 (9.1) 65.8 (4.6) 65.7 (2.6) 73.0 (6.6)
USDA APHIS VS / 7 

Section I: Population Estimates–A. General Management

Rams were the most common additions to fl ocks in 2010 (21.9 percent of ram inventory 

were new additions). By comparison, 7.8 percent of ewes were new additions. 

A.2.c. Percentage of sheep and lambs added during 2010, by type of sheep added and 

by fl ock size: 

Percent Sheep and Lambs*

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Ewes 1 year 

and older 17.2 (11.4) 5.6 (0.9) 5.4 (1.1) 7.8 (2.3)

Rams 1 year 

and older 18.7 (2.4) 24.7 (2.5) 22.6 (2.7) 21.9 (1.5)

Lambs less than 

1 year old of either 

gender

38.5 (34.1) 3.2 (0.9) 5.8 (1.5) 12.9 (8.3)

*Number of ewes, rams, or lambs added as a percentage of sheep inventory on January 1, 2011, including 

lambs born in 2010.
8 / Sheep 2011

Section I: Population Estimates–A. General Management

3. Operations with no fl ock additions in 2010

Producers sometimes inadvertently bring disease onto their operations through new 

animal additions to their fl ocks. A percentage of producers chose to minimize their risk of 

introducing new disease by not adding new animals to their fl ocks, other than by natural 

birth. The longer an operation goes without adding animals, the higher the certainty that 

no asymptomatic, but infected, animals exist in the fl ock. Operations that did not add any 

sheep during 2010 were considered “closed” fl ocks. 

The average number of years since new animals were added to the fl ock varied by age 

and gender of sheep, but not across fl ock types. For example, on average, rams had 

not been added to closed operations for 3.7 years, while ewes and lambs had not been 

added to the closed operations for 9.0 and 8.4 years, respectively.

A.3.a. For operations that did not add any sheep during 2010, average number of years 

since last sheep addition, by type of sheep and by primary fl ock type:

Average Number of Years

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot 

All 

operations

Sheep type Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error

Ewes 1 year 

and older 7.2 (1.6) 10.1 (1.3) 9.2 (0.8) 5.9 (1.2) 9.0 (0.6)

Rams 1 year 

and older 2.5 (0.2) 3.2 (0.3) 4.1 (0.3) 2.8 (0.2) 3.7 (0.2)

Lambs less than 

1 year old of 

either gender

7.5 (2.3) 9.0 (1.5) 9.1 (1.3) 5.0 (1.3) 8.4 (1.0)
USDA APHIS VS / 9 

Section I: Population Estimates–A. General Management

Of the 73.5 percent of operations that did not add ewes during 2010, nearly one-third 

(31.5 percent) had not added ewes in 10 or more years. Of the 55.4 percent of operations 

that did not add rams during 2010, nearly half (44.5 percent) had added them in the 

previous 1 to 2 years. Of the 33.0 percent of operations that did not add any sheep during 

2010 (table A.2.a), 41.4 percent had added sheep or lambs in the previous 1 to 2 years.

A.3.b. For operations that did not add any sheep during 2010, percentage of operations 

by number of years since the following sheep types were added:

Percent Operations

 Number of years

1–2 3–9 10 or more All operations

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Ewes 1 year 

and older 23.5 (4.0) 45.1 (4.9) 31.5 (4.6) 73.5 (1.9)

Rams 1 year 

and older 44.5 (4.3) 51.3 (4.3) 4.2 (1.6) 55.4 (2.1)

Lambs less 

than 

1 year old of 

either gender

29.4 (5.5) 47.5 (6.2) 23.1 (5.3) 70.7 (2.0)

Any 41.6 (2.5) 45.5 (2.5) 12.9 (1.6) 33.0 (2.1)
10 / Sheep 2011

Section I: Population Estimates–A. General Management

4. Contact with other animals

Direct contact with sheep from another operation (or their feed or manure), or sharing 

air space with another fl ock, such as through shared grazing land, at shows, and during 

breeding, pose risks for disease transmission. 

During 2010, sheep on 50.2 percent of all operations had contact with other operations’ 

sheep. Sheep on one-third of operations (33.7 percent) had contact with sheep from 

other operations while at shows, exhibitions, or through breeding prior to returning home. 

A.4.a. Percentage of operations in which sheep had contact with sheep from another 

operation during 2010, by type of contact and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Contact type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

At shows, 

exhibitions, 

breeding, etc., then 

returned to operation

13.5 (4.5) 26.1 (4.2) 35.4 (2.6) 46.2 (7.0) 33.7 (2.1)

Grazed with sheep 

from another 

operation

24.2 (5.3) 11.5 (3.0) 8.4 (1.4) 11.5 (4.5) 9.9 (1.2)

Had fence-line 

contact with sheep 

from another 

operation

42.6 (8.4) 20.8 (3.4) 9.6 (1.5) 8.5 (3.7) 13.1 (1.3)

Had contact with 

sheep visiting from 

another operation

21.4 (7.2) 13.7 (2.9) 23.5 (2.3) 28.2 (6.2) 21.8 (1.8)

Other 1.6 (1.5) 2.5 (1.0) 2.4 (0.8) 2.8 (2.2) 2.4 (0.6)

Any 64.7 (8.9) 47.9 (4.7) 49.0 (2.7) 57.7 (6.8) 50.2 (2.2)
USDA APHIS VS / 11 

Section I: Population Estimates–A. General Management

Just over one-third of operations whose sheep had opportunities for contact with sheep 

from other operations (34.6 percent) made efforts to decrease nose-to-nose contact with 

sheep from other operations.

A.4.b. For operations with sheep that had opportunities for contact with sheep from other 

operations, percentage of operations that made efforts to decrease nose-to-nose contact 

with sheep from other operations, by primary fl ock type: 

Percent Operations 

Primary Flock Type 

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot 

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

20.7 (6.0) 30.2 (6.3) 36.3 (3.9) 36.8 (9.2) 34.6 (3.0)

Cats pose a risk of transmitting diseases (such as toxoplasmosis) to sheep by defecating 

in or around sheep areas or feed, and by giving birth. Nearly all operations had some 

type of cat present during 2010. The majority of operations had either outdoor domestic 

or indoor cats with outside access (79.2 percent) or feral or stray cats (74.5 percent). 

A.4.c. Percentage of operations by type of cats present during 2010, and by primary fl ock 

type: 

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot 

All 

operations

Cat type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Outdoor 

domestic or 

indoor with 

outside access

36.7 (8.4) 75.4 (4.2) 83.7 (2.1) 72.8 (6.4) 79.2 (1.8)

Feral or stray 50.1 (8.2) 72.0 (4.3) 75.4 (2.4) 84.0 (5.1) 74.5 (1.9)

Wild or exotic 

(e.g., bobcats) 53.6 (8.5) 46.6 (4.5) 24.3 (2.2) 11.1 (4.7) 28.9 (1.8)

Any litters 

of kittens 21.4 (4.8) 39.7 (4.6) 49.2 (2.7) 52.1 (6.9) 46.4 (2.1)

Any cats 74.2 (9.8) 91.1 (3.1) 95.6 (1.3) 98.2 (1.2) 94.1 (1.1)
12 / Sheep 2011

Section I: Population Estimates–A. General Management

Only 4.4 percent of operations with domestic cats discarded the contents of cat litter 

boxes into the sheep-raising area. 

 A.4.d. Of operations with cats during 2010, percentage of operations that discarded the 

content of cat litter boxes into the sheep-raising area, by primary fl ock type:

Percent Operations 

Primary Flock Type 

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot 

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

0.0 (—) 5.7 (2.6) 4.7 (1.2) 0.5 (0.4) 4.4 (1.0)

5. Rodent control

Rodents contribute to the spread of disease and are attracted to stored livestock feed. 

Rodent fecal contamination of sheep feed can serve as a potential source of pathogens 

for sheep; therefore, rodent control is an important part of biosecurity on operations. The 

majority of operations (79.2 percent) had outdoor domestic cats or indoor domestic cats 

with outside access. It is assumed these cats provided some rodent control. Otherwise, a 

majority of operations (63.4 percent) used traps, bait, and/or poison as rodent control.

A.5. Percentage of operations by method used to control rats and mice during 2010, and 

by primary fl ock type: 

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Control method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Cats* 36.7 (8.4) 75.4 (4.2) 83.7 (2.1) 72.8 (6.4) 79.2 (1.8)

Dogs 50.4 (8.1) 24.9 (4.0) 25.9 (2.5) 29.4 (6.3) 27.1 (2.0)

Traps, bait, 

and/or poison 35.5 (6.4) 57.9 (4.6) 67.1 (2.6) 61.0 (6.7) 63.4 (2.1)

Professional 

exterminator 3.4 (1.5) 1.0 (0.7) 1.9 (0.7) 3.4 (2.7) 1.9 (0.5)

Other 0.0 (—) 1.4 (1.1) 3.3 (0.9) 0.8 (0.8) 2.5 (0.7)

Any of the above 85.3 (4.4) 92.2 (2.7) 97.3 (0.9) 90.0 (4.3) 95.1 (0.9)

*Outdoor domestic cats or indoor cats with outside access.
USDA APHIS VS / 13 

Section I: Population Estimates–A. General Management

6. Visitors 

Visitors—especially those who have contact with animals from other operations—can 

introduce disease agents via their boots, clothing, vehicles, or other equipment. As 

people travel more frequently throughout the world, the risk of inadvertent or intentional 

introduction of disease agents foreign to the United States increases.

The majority of operations (97.1 percent), and all large operations, had some type of 

visitor to the operation during 2010. 

A.6.a. Percentage of operations by type of visitor on the operation during 2010, and by 

fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Visitor type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Other sheep producers 69.0 (2.6) 67.2 (3.3) 80.6 (4.5) 69.2 (2.0)

Federal/State 

veterinarian or animal 

health worker

21.0 (2.3) 14.3 (2.2) 21.9 (4.0) 19.4 (1.7)

Extension agent or 

university veterinarian 10.0 (1.6) 18.8 (2.6) 27.7 (4.6) 13.2 (1.3)

Private or company 

veterinarian 54.0 (2.8) 54.9 (3.2) 68.8 (4.8) 55.1 (2.1)

Nutritionist 12.7 (1.9) 19.4 (2.5) 27.7 (4.5) 15.3 (1.5)

Customer (private 

individual) to purchase 

meat, wool, or other 

sheep products

52.3 (2.8) 47.9 (3.2) 47.2 (4.6) 50.9 (2.1)

Sheep buyer or dealer 31.0 (2.6) 32.3 (3.2) 51.0 (5.1) 32.5 (2.0)

Renderer 2.9 (0.9) 1.7 (0.8) 1.1 (0.7) 2.5 (0.7)

Shearer 64.5 (2.7) 78.9 (3.1) 92.3 (3.5) 69.7 (2.0)

Other visitors 

(neighbors, friends, 

school fi eld trips, 4-H 

group, hunters, etc.)

79.0 (2.2) 71.2 (3.4) 84.2 (4.3) 77.4 (1.8)

Any 97.3 (0.8) 95.9 (2.0) 100.0 (0.0) 97.1 (0.8)
14 / Sheep 2011

Section I: Population Estimates–A. General Management

0 20 40 60 80 100
USDA APHIS VS / 15 

Section I: Population Estimates–A. General Management

Of the 97.1 percent of operations that had visitors during 2010 (table A.6.a), 96.6 percent 

allowed the visitors access to sheep-raising areas. Other shee p producers were allowed 

to enter the sheep-raising areas on 84.2 percent of operations. 

A.6.b. For operations that had visitors during 2010, percentage of operations that allowed 

the visitors access to sheep-raising areas, by type of visitor and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Visitor Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Other sheep producers 84.0 (2.5) 85.4 (3.0) 83.1 (5.3) 84.2 (1.9)

Federal/State 

veterinarian or animal 

health worker

78.8 (5.3) 80.1 (6.0) 74.5 (11.1) 78.7 (4.2)

Extension agent or 

university veterinarian 78.6 (7.4) 84.6 (6.6) 82.5 (9.8) 81.3 (4.6)

Private or company 

veterinarian 89.3 (2.7) 90.1 (2.6) 75.5 (6.7) 88.4 (2.0)

Nutritionist 56.6 (9.4) 54.6 (7.8) 65.5 (10.5) 57.2 (5.8)

Customer (private 

individual) to purchase 

meat, wool, or other 

sheep products

71.3 (3.7) 68.4 (4.8) 72.2 (6.2) 70.7 (2.9)

Sheep buyer or dealer 82.2 (4.1) 85.6 (3.7) 81.9 (4.3) 83.0 (2.9)

Renderer 36.9 (16.3) 41.7 (23.7) 46.9 (30.2) 38.1 (13.6)

Shearer 93.1 (1.8) 91.9 (2.0) 89.4 (2.4) 92.5 (1.3)

Other visitors 

(neighbors, friends, 

school fi eld trips, 4-H 

group, hunters, etc.)

84.9 (2.3) 90.2 (2.0) 86.7 (3.3) 86.2 (1.7)

Any 96.4 (1.1) 97.2 (1.2) 97.1 (1.0) 96.6 (0.8)
16 / Sheep 2011

Section I: Population Estimates–A. General Management

Over one-fourth of operations in which visitors entered the sheep-raising area always had 

visitors park away from sheep areas. 

A.6.c. For operations in which visitors entered the sheep-raising area during 2010, 

percentage of operations by biosecurity measure required for visitors and by frequency 

that biosecurity measures were performed before visitors entered: 

Percent Operations

Frequency

Always Sometimes Never

Biosecurity measure Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Total

Change into clean 

clothes or coveralls 4.4 (0.9) 8.2 (1.2) 87.4 (1.5) 100.0

Use a footbath before entry 1.2 (0.4) 3.5 (0.8) 95.3 (0.9) 100.0

Change into clean boots 

or use shoe covers 5.9 (1.1) 14.3 (1.6) 79.8 (1.8) 100.0

Scrub footwear before or 

immediately after entry 2.2 (0.6) 8.9 (1.3) 88.9 (1.4) 100.0

Wash hands or use hand 

sanitizer before handling 

sheep

5.2 (1.0) 9.2 (1.2) 85.6 (1.5) 100.0

Park away from sheep area 28.3 (2.0) 12.0 (1.4) 59.7 (2.2) 100.0
USDA APHIS VS / 17 

Section I: Population Estimates–A. General Management

A.6.d. For operations in which visitors entered the sheep-raising area during 2010, 

percentage of operations by biosecurity measure always or sometimes required before 

visitors were allowed to enter sheep-raising area, and by fl ock size: 

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Biosecurity measure Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Change into clean 

clothes or coveralls 13.8 (2.0) 10.4 (2.0) 7.6 (2.0) 12.6 (1.5)

Use a footbath 

before entry 4.3 (1.1) 6.5 (1.5) 2.9 (1.1) 4.7 (0.9)

Change into clean 

boots or use shoe 

covers

21.3 (2.4) 20.3 (2.2) 8.9 (2.6) 20.2 (1.8)

Scrub footwear before 

or immediately after 

entry

12.2 (1.9) 10.3 (2.2) 2.1 (0.9) 11.1 (1.4)

Wash hands or use 

hand sanitizer before 

handling sheep

15.3 (2.1) 13.4 (2.1) 7.9 (2.1) 14.4 (1.5)

Park away from 

sheep area 41.8 (2.9) 41.3 (3.4) 19.9 (3.3) 40.3 (2.2)

Photograph courtesy of Camilla Kristensen.
18 / Sheep 2011

Section I: Population Estimates–A. General Management

7. Housing

Nearly half of all operations (48.9 percent) had no housing structure for the majority of 

their ewes during summer 2010. During winter, only 26.5 percent of operations had no 

structure for the majority of their ewes; this percentage dropped to 13.6 percent during 

lambing.

A.7.a. Percentage of operations by type of housing structure used for the majority of 

ewes during 2010, and by season: 

Percent Operations

Season

Winter Summer Lambing

Housing structure Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Four walls and roof with door 

closed most of the time 12.4 (1.4) 0.7 (0.3) 30.5 (1.9)

Four walls and roof with door 

open most of the time 33.4 (2.0) 22.5 (1.9) 34.6 (2.1)

Roof and three or fewer walls 

(e.g., loafi ng shed) 27.8 (1.9) 28.0 (2.0) 21.3 (1.7)

None 26.5 (1.7) 48.9 (2.1) 13.6 (1.4)

Total 100.0 100.0 100.0
USDA APHIS VS / 19 

Section I: Population Estimates–A. General Management

In winter 2010, a higher percentage of operations in the East region than in the West 

and Central regions housed the majority of their ewes in a structure with four walls and 

roof with a door either open or closed most of the time. In the West region, the highest 

percentage of operations provided a structure with roof and three or fewer walls for the 

majority of their ewes during winter. In summer, no structure was provided for the majority 

of ewes on 46.5 percent of operations in the West region, 60.1 percent in the Central 

region, and 41.8 percent in the East region.

A.7.b. Percentage of operations by housing structure used for the majority of ewes during 

winter and summer 2010, and by region:

Percent Operations

Region

West Central East

Housing structure Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Winter

Four walls and roof with door 

closed most of the time 1.8 (1.4) 6.2 (1.6) 20.2 (2.6)

Four walls and roof with door 

open most of the time 22.9 (4.6) 24.3 (2.7) 43.2 (3.2)

Roof and three or fewer walls 

(e.g., loafi ng shed) 48.4 (5.4) 30.4 (3.2) 19.2 (2.5)

None 26.9 (4.5) 39.1 (3.2) 17.4 (2.1)

Total 100.0 100.0 100.0

Summer

Four walls and roof with door 

closed most of the time 0.0 (—) 1.0 (0.8) 0.6 (0.4)

Four walls and roof with door 

open most of the time 14.9 (4.0) 11.0 (2.1) 33.0 (3.1)

Roof and three or fewer walls 

(e.g., loafi ng shed) 38.6 (5.3) 27.9 (3.3) 24.6 (2.7)

None 46.5 (5.3) 60.1 (3.3) 41.8 (3.1)

Total 100.0 100.0 100.0
20 / Sheep 2011

Section I: Population Estimates–A. General Management

Over 40 percent of herded/open range operations provided no structure during lambing 

season, while over half of all other fl ock types provided a structure with four walls and 

roof. 

A.7.c. Percentage of operations by housing structure used for the majority of ewes for 

lambing during 2010, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Housing 

structure Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Four walls and 

roof with door 

closed most of 

the time

7.8 (2.7) 24.3 (3.9) 31.0 (2.4) 49.1 (7.0) 30.5 (1.9)

Four walls and 

roof with door 

open most of 

the time

20.7 (6.7) 30.9 (4.2) 38.6 (2.7) 19.5 (5.1) 34.6 (2.1)

Roof and three 

or fewer walls 

(e.g., loafi ng 

shed)

31.3 (8.5) 24.7 (4.3) 19.1 (2.1) 26.2 (6.2) 21.3 (1.8)

None 40.1 (8.8) 20.1 (3.7) 11.3 (1.7) 5.3 (2.9) 13.6 (1.4)

Total 100.0 100.0 100.0 100.0 100.0

Photograph courtesy of Camilla Kristensen.
USDA APHIS VS / 21 

Section I: Population Estimates–A. General Management

8. Manure handling

The majority of operations (79.4 percent) disposed of manure by applying it to land 

owned or rented by the operation. 

A.8.a. Percentage of operations by method used to dispose of manure, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Applied to land either 

owned or rented by 

the operation

79.7 (2.2) 82.2 (2.9) 64.8 (5.0) 79.4 (1.7)

Sold or received other 

compensation 6.3 (1.4) 7.7 (2.0) 8.1 (2.2) 6.8 (1.1)

Gave away 35.8 (2.7) 25.6 (2.7) 26.3 (3.6) 32.8 (2.0)

Composted 41.4 (2.7) 43.2 (3.2) 26.3 (3.6) 40.9 (2.1)

Other 1.6 (0.7) 2.8 (1.2) 2.7 (1.3) 1.9 (0.6)

Nearly three-fourths of operations (73.6 percent) never used the same equipment to 

handle manure and feed. The percentage of operations by frequency that the same 

equipment was used to handle manure and feed did not vary substantially by fl ock size or 

fl ock type (data not shown).

A.8.b. Percentage of operations by frequency that the same equipment was used to 

handle manure and feed:

Percent Operations

Frequency

Routinely Sometimes/rarely Never

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Total

11.1 (1.3) 15.4 (1.5) 73.6 (1.9) 100.0
22 / Sheep 2011

Section I: Population Estimates–A. General Management

For the 26.5 percent of operations that routinely or sometimes/rarely used the same 

equipment to handle manure and feed (table A.8.b), the majority of operations 

(70.8 percent) washed equipment used for both manure and feed with water and steam 

only. 

A.8.c. For operations that routinely or sometimes/rarely used the same equipment to 

handle manure and feed, percentage of operations by equipment cleaning procedure 

used prior to handling feed:

Cleaning procedure Percent operations Std. error

Wash equipment with 

water or steam only 70.8 (3.5)

Chemically disinfect only 1.1 (0.8)

Wash equipment and 

chemically disinfect 2.0 (1.0)

Other 22.5 (3.3)

None 3.5 (1.2)

Total 100.0
USDA APHIS VS / 23 

Section I: Population Estimates–A. General Management

9. Offi cial fl ock identifi cation and ear tags

Participation in the Scrapie Eradication Program is mandatory and requires sheep and 

goat producers, dealers, markets, and slaughter plants to identify certain sheep and 

goats. Most sheep and goats must be offi cially identifi ed prior to sale or transport from 

the place of birth. Records on tags or other offi cial identifi cation (ID), as well as records 

on sales and acquisitions, must be kept for 5 years. 

Nearly all operations (92.0 percent) had a fl ock ID number assigned by the USDA’s 

APHIS. A lower percentage of small operations (90.9 percent) had an offi cially assigned 

fl ock ID number than large operations (97.1 percent). 

A.9.a. Percentage of operations that had an offi cial fl ock ID number or used offi cial 

scrapie program ear tags, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Offi cial fl ock ID 90.9 (1.7) 94.0 (1.8) 97.1 (1.2) 92.0 (1.3)

Scrapie program 

ear tag 87.9 (1.9) 89.0 (2.1) 94.0 (1.8) 88.6 (1.4)

A.9.b. Percentage of operations that had an offi cial fl ock ID number or used offi cial 

scrapie program ear tags, by region:

Percent Operations

Region

West Central East

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Offi cial fl ock ID 88.1 (3.5) 90.9 (2.2) 94.2 (1.7)

Scrapie program 

ear tag 81.9 (4.0) 85.9 (2.5) 92.7 (1.9)
24 / Sheep 2011

Section I: Population Estimates–A. General Management

A lower percentage of herded/open range operations had an offi cial fl ock ID or used 

scrapie program ear tags compared with fenced range, pasture, or dry lot/feedlot 

operations. 

A.9.c. Percentage of operations that had an offi cial fl ock ID number or used offi cial 

scrapie program ear tags, by primary fl ock type:

Percent Operations

Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Offi cial fl ock ID 72.9 (10.1) 94.3 (2.2) 92.1 (1.6) 92.0 (4.6)

Scrapie program 

ear tag 56.8 (8.8) 92.6 (2.4) 88.8 (1.8) 89.9 (4.9)

For operations that used offi cial scrapie program ear tags, 99.2 percent of operations 

had the operator or farm worker apply the tags. Only 2.0 percent of operations had tags 

applied at the market. 

A.9.d. For operations that used offi cial scrapie program ear tags, percentage of 

operations by the party responsible for applying tags, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Responsible 

party Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Operator or other 

farm worker 99.0 (0.7) 99.7 (0.3) 99.5 (0.5) 99.2 (0.5)

Veterinarian 0.8 (0.5) 0.0 (—) 0.0 (—) 0.5 (0.4)

Market 1.9 (0.9) 2.9 (1.8) 0.5 (0.5) 2.0 (0.8)
USDA APHIS VS / 25 

Section I: Population Estimates–A. General Management

The only operations that used a veterinarian to apply offi cial scrapie program ear tags 

were in the West region (3.5 percent of operations). 

A.9.e. For operations that used offi cial scrapie program ear tags, percentage of 

operations by party responsible for applying tags, and by region:

Percent Operations

Region

West Central East

Responsible party Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Operator or 

other farm worker 98.1 (1.6) 98.7 (1.2) 99.9 (0.1)

Veterinarian 3.5 (2.4) 0.0 (—) 0.0 (—)

Market 0.2 (0.2) 3.0 (1.8) 1.9 (0.9)

The 3.5 percent of operations in the West region that had a veterinarian apply offi cial 

scrapie program ear tags were pasture operations. None of the herded/open range or dry 

lot operations had the tags applied at the market. 

A.9.f. For operations that used offi cial scrapie program ear tags, percentage of operations 

by party responsible for applying tags, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot 

Responsible party Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Operator or 

other farm worker 100.0 (0.0) 99.7 (0.3) 98.9 (0.7) 100.0 (0.0)

Veterinarian 0.0 (—) 0.0 (—) 0.8 (0.6) 0.0 (—)

Market 0.0 (—) 2.5 (1.9) 2.2 (0.9) 0.0 (—)
26 / Sheep 2011

Section I: Population Estimates–A. General Management

10. ID other than offi cial scrapie program ear tags

Of the 11.4 percent of operations that did not use scrapie program ear tags (table A.9.a), 

72.8 percent indicated that they only sold slaughter lambs and, therefore, were not 

required to apply the offi cial ID. For the 6.0 percent of large operations that did not use 

the scrapie program ear tag (table A.9.a), 46.4 percent did not know they were required to 

offi cially identify sheep before leaving the operation. Only medium and small operations 

reported that they did not use scrapie ear tags because the operation did not move sheep 

off-farm. Nearly one-fourth of operations gave “other” as a reason for not using offi cial ear 

tags. The majority of these operations reported that the tags fell out or the operator forgot 

to use them. 

A.10.a. For operations that did not use scrapie program ear tags, percentage of 

operations by reason for not using the tags, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Reason Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Only sell slaughter 

lambs so not required 

to apply offi cial ID

76.4 (7.7) 63.8 (12.7) 53.6 (16.4) 72.8 (6.5)

Did not move sheep off 

farm so not required to 

apply offi cial ID

68.5 (8.9) 47.0 (14.5) 0.0 (—) 62.5 (7.5)

Did not know operation 

was required to offi cially 

identify sheep before 

they left the operation

26.7 (8.5) 22.8 (10.3) 46.4 (16.4) 26.6 (6.9)

Used another type of 

offi cial ID instead of 

offi cial ear tags

7.3 (4.8) 6.4 (6.0) 9.5 (7.5) 7.2 (3.9)

Other 21.2 (8.5) 27.2 (13.0) 0.0 (—) 21.6 (7.0)
USDA APHIS VS / 27 

Section I: Population Estimates–A. General Management

Just over half of all operations that did not use the scrapie program ear tags 

(53.5 percent) were aware that the tags are available and free. 

A.10.b. For operations that did not use scrapie program ear tags, percentage of 

operations that were aware of the availability of the free scrapie ear tags, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

50.4 (9.1) 63.9 (11.7) 68.8 (13.6) 53.5 (7.5)
28 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

An accurate, annual estimate of the lamb crop is an important measurement of fl ock 

productivity. Nearly all operations can provide their lambing rate, but it is not always clear 

how the rate is measured. For some operations in the largest lamb-producing States, the 

predocking period is an enigma. Therefore, their lambing rate is based on the number 

of lambs tails docked divided by the number of ewes bred in a given year. This method 

of determining the lambing ratio is not as effi cient as maintaining individual-ewe lambing 

records, partly because it cannot be determined whether the majority of lamb losses were 

due to predators, no colostrum, poor mothering, scours, pneumonia, or other causes. 

These losses are diffi cult to prevent if the cause of loss is unknown. 

1. Calculation of lambing rate

The highest percentage of operations (47.3 percent) calculated lambing rates using the 

number of lambs born divided by ewes bred in a given year. The second most common 

method used (29.6 percent of operations) was to use the number of lambs weaned 

divided by ewes bred. Over half of large operations (54.9 percent) calculated lambing 

rates using the number of lambs docked divided by ewes bred, while a similar percentage 

of small operations used lambs born divided by ewes bred. 

B.1.a. Percentage of operations by method of calculating lambing rate, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Lambs born/

ewes bred 53.2 (3.0) 38.7 (3.3) 18.1 (3.2) 47.3 (2.2)

Lambs docked/

ewes bred 9.1 (1.7) 19.6 (2.8) 54.9 (4.9) 14.7 (1.4)

Lambs weaned/

ewes bred 29.0 (2.8) 33.8 (3.4) 19.4 (4.0) 29.6 (2.1)

Other 8.7 (1.7) 7.9 (1.6) 7.7 (2.1) 8.5 (1.2)

Total 100.0 100.0 100.0 100.0

B. Reproduction 

Management
USDA APHIS VS / 29 

Section I: Population Estimates–B. Reproduction Management

0

20

40

60

80

All operations

Large (500 or more)

Medium (100-499)

Small (20-99)
30 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

Lambing-rate calculations in the Central region were split fairly evenly across methods, 

while just over half the operations in the West and East regions calculated lambing rates 

by dividing lambs born by ewes bred (52.8 and 54.5 percent of operations, respectively).

B.1.b. Percentage of operations by method of calculating lambing rate, and by region:

Percent Operations

Region

West Central East

Method Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Lambs born/ewes bred 52.8 (5.6) 33.3 (3.2) 54.5 (3.3)

Lambs docked/ewes bred 18.8 (4.1) 25.7 (2.7) 6.2 (1.7)

Lambs weaned/ewes bred 21.2 (4.7) 33.3 (3.5) 29.9 (3.1)

Other 7.3 (2.8) 7.7 (1.5) 9.4 (2.1)

Total 100.0 100.0 100.0

As expected, a higher percentage of herded/open range operations calculated lambing 

rates by dividing lambs docked by ewes bred compared with other fl ock types.

B.1.c. Percentage of operations by method of calculating lambing rate, and by primary 

fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot 

Method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Lambs born/ewes bred 15.6 (6.0) 34.0 (4.5) 52.2 (2.8) 50.4 (7.3)

Lambs docked/ewes bred 57.0 (6.6) 27.5 (3.9) 10.1 (1.6) 7.5 (3.6)

Lambs weaned/ewes bred 21.1 (4.9) 33.6 (4.7) 28.3 (2.5) 33.4 (7.2)

Other 6.2 (3.0) 4.8 (1.9) 9.4 (1.6) 8.6 (3.6)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 31 

Section I: Population Estimates–B. Reproduction Management

2. Normal or average lambing rate 

More than half of small operations calculated lambing rate by using lambs born/

ewes bred (table B.1.a), while a similar percentage of large operations calculated this 

rate as lambs docked/ewes bred. The average expected lambing rate for operations 

that calculated lambing rate by lambs born/ewes bred was 1.60, while operations 

that calculated lambing rate by lambs docked/ewes bred expected a rate of 1.34. It 

is essential to understand how a lambing rate was calculated when interpreting this 

measure of productivity.

B.2.a. Average expected lambing rate, by method of calculating lambing rate and by fl ock 

size:

Average Lambing Rate

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Method Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error

Lambs born/

ewes bred 1.61 (0.02) 1.60 (0.04) 1.52 (0.06) 1.60 (0.02)

Lambs docked/

ewes bred 1.41 (0.06) 1.38 (0.05) 1.14 (0.05) 1.34 (0.04)

Lambs weaned/

ewes bred 1.42 (0.04) 1.36 (0.04) 1.22 (0.08) 1.40 (0.03)

Other 1.59 (0.04) 1.54 (0.05) 1.28 (0.04) 1.56 (0.04)

Average expected 

lambing rate 1.53 (0.02) 1.47 (0.02) 1.23 (0.04) 1.50 (0.02) 
32 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

The overall expected average lambing rate in the Central region was lower than in the 

East region (1.38 and 1.59, respectively), especially when comparing the lambs weaned 

to ewes bred ratio (1.27 and 1.49, respectively). 

B.2.b. Average expected lambing rate, by method of calculating lambing rate and by 

region:

Average Lambing Rate

Region

West Central East

Method Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error

Lambs born/ewes bred 1.55 (0.05) 1.52 (0.05) 1.66 (0.02)

Lambs docked/ewes bred 1.36 (0.08) 1.28 (0.04) 1.48 (0.07)

Lambs weaned/ewes bred 1.37 (1.1) 1.27 (0.04) 1.49 (0.03)

Other 1.47 (0.07) 1.53 (0.06) 1.60 (0.05)

 Average expected 

lambing rate 1.47 (0.04) 1.38 (0.03) 1.59 (0.02)
USDA APHIS VS / 33 

Section I: Population Estimates–B. Reproduction Management

Overall pasture and dry lot operations expected a higher lambing rate than herded/open 

range or fenced range operations. When calculated by the number of lambs weaned to 

ewes bred, the lambing rate for herded/open range and fenced range operations was 

lower than the rate for pasture operations (1.20, 1.23, and 1.46, respectively). When 

calculated using number of lambs born, there was no difference. 

B.2.c. Average expected lambing rate, by method of calculating lambing rate and by 

primary fl ock type:

Average Lambing Rate 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Method Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error

Lambs born/

ewes bred 1.51 (0.09) 1.54 (0.06) 1.61 (0.02) 1.63 (0.05)

Lambs docked/

ewes bred 1.31 (0.03) 1.20 (0.06) 1.45 (0.05) 1.42 (0.09)

Lambs weaned/

ewes bred 1.20 (0.06) 1.23 (0.05) 1.46 (0.03) 1.40 (1.0)

Other 1.26 (0.04) 1.40 (0.06) 1.59 (0.04) 1.50 (0.03)

 Average expected 

lambing rate 1.32 (0.03) 1.33 (0.04) 1.55 (0.02) 1.52 (0.05)
34 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

3. Lambing season

When the questionnaire for this report was administered, 51.2 percent of operations had 

not yet fi nished lambing. Data for these operations represent the previous year’s lambing 

season (spring/summer/fall 2010, or winter/spring 2011).

B.3. Percentage of operations by season of last completed lambing season, and by 

region:

Percent Operations

Region

West Central East

All

operations

Season Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Spring 2010 38.3 (5.3) 41.1 (3.2) 39.3 (3.1) 39.7 (2.1)

Summer 2010 11.7 (3.5) 5.0 (1.3) 1.7 (0.6) 4.5 (0.8)

Fall 2010 11.9 (3.2) 6.9 (2.0) 5.5 (1.3) 7.0 (1.1)

Winter 2010–11 36.2 (5.3) 28.8 (3.2) 36.2 (3.1) 33.6 (2.1)

Spring 2011 1.9 (1.0) 18.3 (2.9) 17.5 (2.6) 15.2 (1.6)

Total 100.0 100.0 100.0 100.0

4. Breeding management for the last completed lambing season

All operations bred at least some of their own ewes, while just 6.1 percent of operations 

added ewes already bred. 

B.4.a. Percentage of operations by breeding locale and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Locale Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Bred on this 

operation 100.0 (0.0) 100.0 (0.0) 100.0 (0.0) 100.0 (0.0)

Added to this 

operation

already bred

6.0 (1.3) 7.3 (1.9) 3.2 (1.2) 6.1 (1.0)
USDA APHIS VS / 35 

Section I: Population Estimates–B. Reproduction Management

Overall, 99.2 percent of ewes bred in the last completed lambing season were bred on 

the operation, and 0.8 percent were added to the operation already bred. 

B.4.b. Percentage of ewes by breeding locale and by fl ock size:

Percent Ewes*

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Locale Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Bred by this operation 98.6 (0.5) 98.6 (0.6) 99.8 (0.1) 99.2 (0.2)

Added to this 

operation already bred 1.4 (0.5) 1.4 (0.6) 0.2 (0.1) 0.8 (0.2)

Total 100.0 100.0 100.0 100.0

*As a percentage of total bred ewes in last completed lambing season.

Photograph courtesy of American Sheep Industry Association.
36 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

Overall, 86.9 percent of operations had fi rst-lambing ewes in 2010. 

B.4.c. Percentage of operations that had fi rst-lambing ewes, by fl ock size:

Percent Operations 

 Flock Size 

Small 

(20-99)

Medium

(100 - 499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

86.6 (2.0) 87.9 (2.4) 85.1 (4.8) 86.9 (1.5)

Newly added bred ewes and fi rst-lambing ewes can be potential sources of infection 

for the rest of the fl ock. Overall, 17.5 percent of operations that added bred ewes also 

separated these ewes from the fl ock until after they had lambed. Additionally, 

20.2 percent of operations separated fi rst-lambing ewes from the rest of the fl ock until 

after they had lambed. 

B.4.d. For operations that added bred ewes or that had any fi rst-lambing ewes, 

percentage of operations that separated the ewes from the fl ock until after they had 

lambed: 

Percent operations Std. error

Ewes already bred 

when added 17.5 (6.4)

First-lambing ewes 20.2 (1.8)
USDA APHIS VS / 37 

Section I: Population Estimates–B. Reproduction Management

Overall, 93.0 percent of bred ewes lambed with full-term births. Of these, 17.8 percent 

were fi rst-lambing ewes.

B.4.e. Percentage of all bred ewes that lambed with full-term births, and percentage of 

these ewes that were fi rst-lambing ewes, by fl ock size: 

Percent Ewes

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

All bred ewes 

that lambed 92.9 (0.7) 93.2 (0.7) 92.9 (0.7) 93.0 (0.4)

First-lambing ewes 19.2 (0.9) 16.5 (0.9) 17.9 (1.2) 17.8 (0.7)

5. Lambing outcome

Note: Tables in this section apply to the last completed lambing season.

Overall, 96.4 percent of lambs were born alive. This percentage was similar across fl ock 

types.

B.5.a. Percentage of lambs born alive, by primary fl ock type:

Percent Lambs*

Primary Flock Type 

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

97.5 (0.3) 97.0 (0.3) 95.8 (0.2) 95.0 (0.5) 96.4 (0.1)

*Number of lambs born alive as a percentage of all lambs born.
38 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

B.5.b. Percentage of operations that docked lambs, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

86.1 (2.0) 87.2 (2.8) 95.5 (3.3) 86.9 (1.6)

B.5.c. Percentage of operations that docked lambs, by primary fl ock type:

Percent Operations

Primary Flock Type 

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

86.4 (8.4) 86.4 (3.8) 88.0 (1.9) 79.3 (6.4)

When using the number of all lambs born, the lambing rate was higher for small and 

medium operations (1.51 and 1.45, respectively) than it was for large operations (1.28). 

The lamb weaning rate was highest for small operations (1.33) and lowest for large 

operations (1.06). The calculated lambing rate for all operations, using number of lambs 

born, was 1.38, and 1.16 for lambs weaned and 1.10 for lambs docked. The average 

number of lambs docked per ewe bred was limited to operations that used docking to 

measure lambing rates, with the assumption that these operations would likely dock all 

lambs. 

B.5.d. Average number of lambs born, weaned, and docked per ewe bred for the last 

completed lambing season, by fl ock size:

Average Lambing Rate 

 Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

No.

Std. 

error No.

Std. 

error No.

Std. 

error No.

Std. 

error

Born 1.51 (0.0) 1.45 (0.0) 1.28 (0.0) 1.38 (0.0)

Weaned 1.33 (0.0) 1.23 (0.0) 1.06 (0.0) 1.16 (0.0)

Docked* 1.30 (0.1) 1.21 (0.1) 1.06 (0.0) 1.10 (0.0)

*For operations that use docking to measure lambing rate.
USDA APHIS VS / 39 

Section I: Population Estimates–B. Reproduction Management

Lambing and weaning ratios were higher in pasture and dry lot/feedlot fl ocks than in 

herded open/range and fenced range fl ocks.

B.5.e. Average number of lambs born, weaned, and docked per ewe bred, by primary 

fl ock type:

Average Lambing Rate

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

No.

Std. 

error No.

Std. 

error No.

Std. 

error No.

Std. 

error

Born 1.29 (0.0) 1.29 (0.0) 1.48 (0.0) 1.47 (0.0)

Weaned 1.08 (0.0) 1.06 (0.0) 1.28 (0.0) 1.27 (0.0)

Docked* 1.12 (0.1) 1.02 (0.1) 1.24 (0.1) 1.1 (0.1)

*For operations that use docking to measure lambing rate.

Of the lambs born alive, 89.3 percent were weaned and 87.0 percent were docked. Hair 

sheep are normally not docked, and some wool sheep producers choose not to dock 

lambs tails. Some operations that dock only dock certain sheep, such as females or 

replacement ewe lambs.

B.5.f. Percentage of lambs born alive that were weaned and percentage that were 

docked, by fl ock size:

Percent Lambs 

 Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Weaned 92.2 (0.7) 89.2 (1.0) 87.8 (1.4) 89.3 (0.7)

Docked 79.0 (2.5) 83.8 (2.2) 93.5 (0.9) 87.0 (1.0)
40 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

A lower percentage of lambs in pasture fl ocks were docked (83.4 percent) compared with 

lambs in herded/open range fl ocks (92.6 percent). 

B.5.g. Percentage of lambs born alive that were weaned and percentage that were 

docked, by primary fl ock type:

Percent Lambs 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Weaned 87.7 (1.7) 88.8 (1.9) 90.2 (0.8) 89.6 (1.5)

Docked 92.6 (1.5) 90.0 (1.9) 83.4 (1.8) 79.1 (5.4)

6. Low lambing rate

Note: Tables in this section apply to the last completed lambing season.

Roughly one-third of operations had a lower-than-expected lambing rate for the most 

recently completed lamb crop. 

B.6.a. Percentage of operations that had a lower-than-expected lambing rate for the most 

recently completed lamb crop, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

35.8 (2.8) 32.2 (3.3) 48.9 (5.1) 35.7 (2.1)
USDA APHIS VS / 41 

Section I: Population Estimates–B. Reproduction Management

The percentage of operations with a lower-than-expected lambing rate in their most 

recently completed lamb crop did not vary by season of the last completed lambing 

season.

B.6.b. Percentage of operations that had a lower-than-expected lambing rate for the most 

recently completed lamb crop, by season:

Percent Operations

Lambing Season

Fall Winter Spring Summer

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

36.1 (7.7) 29.8 (3.6) 39.4 (2.9) 34.7 (8.5) 35.7 (2.1)

A higher percentage of operations in the East region (41.2 percent) had a lower-thanexpected lambing rate for the most recently completed lamb crop compared with 

operations in the West region (25.1 percent). 

B.6.c. Percentage of operations that had a lower-than-expected lambing rate for the most 

recently completed lamb crop, by region:

Percent Operations

Region

West Central East

Percent Std. error Percent Std. error Percent Std. error

25.1 (4.7) 33.0 (3.2) 41.2 (3.3)
42 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

Of operations with a lower-than-expected lambing rate, nearly one-third (32.2 percent) 

indicated that reduced twinning/triplets was the primary cause of the lower rate. Reduced 

twinning/triplets was a primary reason for lower rates in all fl ock types, with the exception 

of herded/open range operations. The highest percentage of herded/open range 

operations reported lamb deaths as the primary reason of the lower rate. A number of 

operations cited “other” as the cause of a lower-than-expected lambing rate. The primary 

reasons they listed were: multiple causes, yearling ewes, or weather (heat/drought). 

There were no measurable differences by fl ock size or by region (data not shown).

B.6.d. For operations with a lower-than-expected lambing rate, percentage of operations 

by primary cause of lower rate, and by fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced

range Pasture

Dry lot/

feedlot

All 

operations

Cause Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Open ewes 

(bred but did 

not take)

24.7 (13.0) 13.2 (5.9) 12.1 (2.9) 14.9 (9.2) 13.0 (2.5)

Abortions 5.8 (4.1) 0.6 (0.6) 3.7 (2.0) 3.1 (3.0) 3.0 (1.4)

Lamb deaths 

(including 

stillborns)

44.0 (13.5) 32.6 (7.4) 27.4 (4.2) 14.7 (9.5) 28.3 (3.4)

Reduced 

twinning/triplets 3.1 (1.8) 29.5 (6.7) 33.9 (4.4) 39.5 (14.7) 32.2 (3.5)

Ram fertility 0.0 (—) 2.6 (2.6) 3.6 (1.7) 3.3 (3.2) 3.2 (1.2)

Other 7.5 (5.0) 16.1 (5.3) 17.0 (3.3) 19.5 (12.0) 16.4 (2.6)

Do not know 14.9 (13.1) 5.4 (4.5) 2.4 (1.5) 4.9 (4.7) 3.9 (1.6)

Total 100.0 100.0 100.0 100.0 100.0
USDA APHIS VS / 43 

Section I: Population Estimates–B. Reproduction Management

0 10 20 30 40
44 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

Overall, 17.1 percent of operations did not know the cause of lamb deaths in the 

last completed lamb crop. Compared with other fl ock sizes, a higher percentage of 

large operations indicated predators were the primary cause of lamb deaths. A higher 

percentage of small operations (20.7 percent) did not know the primary cause of lamb 

deaths compared with medium or large operations (9.7 and 5.2 percent, respectively). 

For operations in which disease was the primary cause of death, pneumonia or parasites 

were the leading causes. “Other” causes of death were primarily starvation or multiple 

reasons. 

B.6.e. Percentage of operations by primary cause of lamb deaths, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Cause Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Predators 6.7 (1.4) 19.4 (3.0) 42.8 (5.1) 12.0 (1.3)

Weather (temperature, 

lightning, fl ood, etc.) 21.5 (2.4) 21.8 (3.0) 28.4 (3.5) 22.0 (1.8)

Disease 13.9 (1.9) 22.1 (2.5) 9.6 (2.4) 15.6 (1.4)

Other 28.9 (2.6) 25.1 (2.9) 14.1 (3.0) 27.1 (1.9)

Do not know 20.7 (2.4) 9.7 (1.8) 5.2 (3.2) 17.1 (1.7)

No lamb deaths 8.3 (1.6) 1.9 (0.8) 0.0 (0.0) 6.2 (1.1)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 45 

Section I: Population Estimates–B. Reproduction Management

A lower percentage of herded/open range operations than pasture operations (6.1 and 

16.1 percent, respectively) indicated disease was the primary cause of lamb deaths in the 

last completed lamb crop. Just over 40 percent of operations listed “other” as the primary 

cause of death, which primarily included starvation or multiple reasons.

B.6.f. Percentage of operations by primary cause of lamb deaths, and by primary fl ock 

type:

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Primary cause Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Predators 22.7 (5.0) 19.3 (3.4) 10.4 (1.6) 3.4 (2.7)

Weather 

(temperature, 

lightning, fl ood, etc.)

38.6 (8.4) 28.8 (4.3) 19.7 (2.2) 17.4 (5.2)

Disease 6.1 (3.6) 17.5 (3.5) 16.1 (1.8) 12.9 (4.4)

Other 24.3 (9.1) 13.1 (3.1) 29.2 (2.5) 41.1 (6.8)

Do not know 8.3 (6.3) 16.7 (3.7) 17.9 (2.2) 16.3 (5.3)

No lamb deaths 0.0 (—) 4.6 (2.1) 6.8 (1.5) 8.9 (5.0)

Total 100.0 100.0 100.0 100.0
46 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

A higher percentage of operations that lambed in spring (15.7 percent) reported predators 

as the primary cause of lamb death compared with operations that lambed in winter 

(6.4 percent). 

B.6.g. Percentage of operations by primary cause of lamb deaths, and by lambing 

season:

Percent Operations

Lambing Season

Fall Winter Spring Summer

Primary cause Pct.

Std.

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Predators 10.8 (3.9) 6.4 (1.8) 15.7 (2.0) 14.7 (5.3)

Weather (temperature, 

lightning, fl ood, etc.) 12.0 (4.6) 27.5 (3.5) 20.1 (2.4) 23.6 (7.1)

Disease 15.9 (5.6) 11.8 (2.2) 17.1 (2.0) 16.6 (7.5)

Other reasons 28.3 (7.3) 30.2 (3.5) 24.8 (2.6) 25.0 (8.3)

Do not know 22.2 (7.7) 17.6 (3.2) 16.6 (2.3) 15.2 (7.0)

No lamb deaths 10.7 (5.0) 6.6 (2.2) 5.7 (1.5) 5.0 (4.8)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 47 

Section I: Population Estimates–B. Reproduction Management

7. Lamb supplements

Note: Tables in this section apply to the last completed lamb crop.

Feeding lambs high-quality colostrum following birth helps ensure the transfer of 

antibodies needed to protect lambs against disease. Usually lambs receive adequate 

colostrum from their mothers. Sometimes it is necessary to supplement newborns using 

other colostrum sources. Over half of all operations (54.5 percent) gave lambs colostrum 

from a source other than the lambs’ mothers. 

B.7.a. Percentage of operations that gave lambs colostrum from a source other than the 

lambs’ mothers during 2010, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

50.9 (2.8) 64.3 (3.5) 55.2 (5.2) 54.5 (2.2)

A higher percentage of fenced range and pasture operations (54.6 and 56.0 percent, 

respectively) gave lambs colostrum following birth from a source other than their mothers 

compared with herded/open range operations (28.0 percent). There were no substantial 

differences by region (data not shown). 

B.7.b. Percentage of operations that gave lambs colostrum from a source other than the 

lambs’ mothers during 2010, by primary fl ock type:

Percent Operations

Primary Flock Type

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

28.0 (6.1) 54.6 (4.7) 56.0 (2.7) 54.2 (7.1)
48 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

The majority of operations that gave lambs colostrum from a source other than the lambs’ 

mothers (73.2 percent) used sheep colostrum from ewes on their own operation. The 

second most commonly used source of colostrum was dried sheep colostrum, used by 

about one-third of operations (32.2 percent). A higher percentage of operations that gave 

cow colostrum used colostrum from a herd that was not tested for Johne’s disease or 

had an unknown Johne’s-disease status, compared with operations that used colostrum 

from a herd that was tested for Johne’s disease (17.6 and 3.2 percent of operations, 

respectively).

B.7.c. For operations that gave lambs colostrum from a source other than the lambs’ 

mothers during 2010, percentage of operations by source of colostrum:

Source Percent operations Std. error

Sheep colostrum from own 

operation 73.2 (2.4)

Liquid sheep colostrum from 

outside source 3.2 (1.0)

Dried colostrum 32.2 (2.6)

Any cow colostrum 20.8 (2.2)

Cow colostrum from a herd

tested for Johne’s disease 3.2 (1.0)

Cow colostrum from a herd not 

tested for Johne’s disease or 

did not know if tested

17.6 (2.0)

Goat colostrum 8.6 (1.6)

Other 4.9 (1.2)
USDA APHIS VS / 49 

Section I: Population Estimates–B. Reproduction Management

When colostrum was fed, it was given within 2 hours following birth by 56.2 percent of 

operations. A higher percentage of small operations (63.4 percent) gave colostrum within 

2 hours following birth compared with medium or large operations (43.5 and 

42.6 percent, respectively). Less than 5 percent of operations gave colostrum 9 or more 

hours following birth. There was no variation across fl ock types in time of fi rst colostrum 

feeding (data not shown). 

B.7.d. For operations that gave lambs colostrum from a source other than the lambs’ 

mothers during 2010, percentage of operations by average number of hours following 

birth that lambs were typically given/fed their fi rst colostrum, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Time until 

fi rst feeding (hr) Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Less than 2 63.4 (3.8) 43.5 (3.8) 42.6 (6.6) 56.2 (2.7)

2 to <5 27.2 (3.5) 42.3 (3.9) 35.0 (5.7) 32.2 (2.6)

5 to 9 6.2 (1.9) 8.2 (1.9) 17.1 (4.3) 7.5 (1.4)

9 or more 3.2 (1.3) 6.0 (1.7) 5.3 (2.6) 4.2 (1.0)

A variety of liquid diets are commonly fed to lambs unable to obtain the necessary 

nutrition from their mothers. Properly pasteurizing and handling milk reduces pathogen 

loads without affecting milk quality. Nearly three-fourths of all operations supplemented 

lambs with milk or milk replacer. 

B.7.e. Percentage of operations that supplemented lambs with milk or milk replacer, by 

fl ock size:

Percent Operations 

Flock Size (number of ewes)

Small

(20–99)

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

73.4 (2.6) 83.4 (3.1) 70.3 (5.3) 73.2 (2.0)
50 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

A lower percentage of operations in the Central region (65.5 percent) supplemented 

lambs with milk or milk replacer compared with operations in the East region 

(80.1 percent). There was no difference by fl ock type (data not shown).

B.7.f. Percentage of operations that supplemented lambs with milk or milk replacer, by 

region:

Percent Operations 

Region 

West Central East

Percent Std. error Percent Std. error Percent Std. error

68.7 (5.1) 65.5 (3.4) 80.1 (2.6)

Nearly all operations that supplemented lambs (94.6 percent) used dried milk or milk 

replacer. A higher percentage of large operations than small operations used sheep milk 

from their own operation to supplement lambs (44.3 and 26.3 percent, respectively).

B.7.g. For operations that supplemented lambs with milk or milk replacer, percentage of 

operations by source of supplemental milk or milk replacer, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Source Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Sheep milk from 

own operation 26.3 (2.9) 28.5 (3.6) 44.3 (5.3) 27.9 (2.2)

Liquid sheep milk 

from outside source 0.0 (0.0) 0.7 (0.5) 0.0 (0.0) 0.2 (0.1)

Dried milk or 

milk replacer 93.6 (1.7) 97.2 (1.0) 95.5 (1.7) 94.6 (1.2)

Cow milk (cows tested 

for Johne’s disease) 2.4 (1.2) 1.8 (0.8) 0.7 (0.6) 2.2 (0.9)

Cow milk (cows not 

tested for Johne’s 

disease or did not know 

if tested)

6.2 (1.6) 7.0 (1.7) 13.9 (3.2) 6.9 (1.2)

Goat milk 10.0 (1.9) 7.7 (2.3) 14.3 (3.2) 9.7 (1.5)

Other 0.8 (0.5) 0.7 (0.5) 0.7 (0.6) 0.7 (0.4)
USDA APHIS VS / 51 

Section I: Population Estimates–B. Reproduction Management

A higher percentage of operations in the East region (3.8 percent) than in the West or 

Central region (0.3 and 0.2 percent, respectively) used cow milk from cows tested for 

Johne’s disease. 

B.7.h. For operations that supplemented lambs with milk or milk replacer, percentage of 

operations by source of supplemental milk or milk replacer, and by region:

Percent Operations

Region

West Central East

Source Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Sheep milk from own

operation 38.0 (6.2) 26.2 (3.3) 26.1 (3.2)

Liquid sheep milk 

from outside source 0.7 (0.7) 0.0 (0.0) 0.1 (0.1)

Dried milk or 

milk replacer 94.8 (3.0) 96.0 (1.2) 93.7 (2.0)

Cow milk (cows 

tested for Johne’s disease) 0.3 (0.2) 0.2 (0.2) 3.8 (1.5)

Cow milk (cows not tested for 

Johne’s disease or did 

not know if tested)

6.1 (3.2) 6.9 (1.7) 7.1 (1.8)

Goat milk 15.8 (5.0) 11.6 (2.2) 6.9 (1.9)

Other 2.8 (2.2) 0.6 (0.6) 0.2 (0.2)
52 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

Feeding pasteurized milk or milk replacer reduces the possibility of disease transmission. 

Nonpasteurized milk can contain a variety of pathogens, including those that cause 

mastitis (e.g., Staphylococcus and Streptococcus species), diarrhea (e.g., Escherichia 

coli, Salmonella species), respiratory disease (e.g., Pasteurella, Mycoplasma species), 

abscesses (Corynebacterium pseudotuberculosis), and a variety of systemic diseases 

(e.g., listeriosis, caprine arthritis-encephalitis, Johne’s disease, brucellosis). 

Pasteurization is especially important if the supplemented milk is pooled from a number 

of ewes or acquired from another fl ock, which can increase the odds of exposing lambs 

to disease. Scrapie may also be transmitted to sheep or goats through milk from infected 

sheep or goats. Pasteurization is unlikely to eliminate scrapie infectivity from milk. As 

a result, milk or colostrum should not be sourced from other sheep or goat herds of 

unknown scrapie status. Nearly all operations that supplemented lambs with fresh milk 

(96.7 percent) did not pasteurize the milk. 

B.7.i. For operations that supplemented lambs with fresh milk, percentage of operations 

by whether supplemented milk was pasteurized:

Pasteurized Percent operations Std. error

Yes 2.5 (1.5)

No 96.7 (1.7)

Don’t know 0.8 (0.8)

8. Ewe synchronization 

Controlled internal drug release (CIDR) devices contain progesterone intended to prevent 

ewes from returning to estrus and ovulating. Once these devices are removed, the ewe 

will ovulate within a few days. CIDRs were approved for use in the United States in 2009. 

A very low percentage of all operations (6.7 percent) used CIDRs in 2010. An especially 

low percentage of large operations (1.5 percent) used CIDRs.

B.8.a. Percentage of operations that used a CIDR progesterone insert as a breeding tool 

in 2010, by fl ock size:

Percent Operations 

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

6.7 (1.4) 8.2 (2.0) 1.5 (0.7) 6.7 (1.1)
USDA APHIS VS / 53 

Section I: Population Estimates–B. Reproduction Management

While 6.7 percent of all operations used CIDRs in 2010, this percentage mainly refl ects 

fenced range, pasture, and dry lot/feedlot operations; less than 1 percent of herded/open 

range operations used CIDRs in 2010. 

B.8.b. Percentage of operations that used a CIDR progesterone insert as a breeding tool 

in 2010, by primary fl ock type:

Percent Operations 

Primary Flock Type 

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

0.7 (0.6) 5.9 (2.3) 6.8 (1.4) 9.1 (4.1)

Three-fourths of the operations that used CIDRs used them for out-of-season breeding. 

“Other” reasons for using CIDRs included preparing lambs for show.

B.8.c. For operations that used a CIDR progesterone insert as a breeding tool in 2010, 

percentage of operations by reason for use:

Reason Percent operations Std. error

For out-of-season breeding 75.7 (7.9)

To synchronize 

estrus in season 49.2 (8.8)

With a gonadotropin (GnRH) 52.1 (8.8)

Other 7.5 (5.1)
54 / Sheep 2011

Section I: Population Estimates–B. Reproduction Management

Nearly all operations that used a CIDR insert (95.6 percent) indicated they would use it 

again.

B.8.d. For operations that used a CIDR progesterone insert as a breeding tool in 2010, 

percentage of operations that would use the insert again:

Use CIDR again? Percent operations Std. error

Yes 95.6 (3.7)

No 0.0 (—)

Don’t know 4.4 (3.7)

Total 100.0
USDA APHIS VS / 55 

Section I: Population Estimates–C. Lambing Management

1. Manure and waste bedding management during lambing

Cleaning the lambing area is crucial in preventing disease transmission from ewes to 

lambs and from ewes to ewes. Periparturient ewes, which may be immunosuppressed, 

and newborn lambs, with immature immune systems, are especially susceptible to 

infectious diseases. At the same time, the tissue and fl uid left by infected ewes after 

giving birth often shed harmful organisms into the environment. Organisms that 

pose such risks include prions (cause of scrapie), Mycobacterium avium subspecies 

paratuberculosis (cause of Johne’s disease), Coxiella burnetii (cause of Q fever), 

Toxoplasma gondii, and various Salmonella species, to name a few. 

Just over one-fourth of operations (25.7 percent) cleaned manure and waste bedding 

from the lambing area either between each lambing (10.9 percent of operations) or 

between two or more lambings (14.8 percent). The remainder of operations either 

cleaned the lambing area at the end of lambing (48.8 percent) or never cleaned the 

lambing area (25.4 percent). A lower percentage of large operations (2.9 percent) than 

small operations (13.1 percent) cleaned the lambing area between each ewe lambing.

C.1.a. Percentage of operations by frequency that manure and waste bedding were 

cleaned from the lambing area during lambing season, and by fl ock size:

Percent Operations 

 Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Cleaning 

frequency Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Between each lambing 13.1 (1.8) 6.7 (2.0) 2.9 (1.2) 10.9 (1.3)

Between two 

or more lambings 14.5 (1.9) 15.6 (2.4) 16.2 (3.2) 14.8 (1.5)

At the end of 

lambing season 48.9 (2.7) 50.7 (3.3) 40.7 (4.1) 48.8 (2.1)

Not cleaned 23.5 (2.4) 27.0 (3.3) 40.3 (4.9) 25.4 (1.9)

Total 100.0 100.0 100.0 100.0

C. Lambing 

Management
56 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

A higher percentage of operations in the West region (18.0 percent) cleaned between 

each lambing compared with operations in the East region (6.4 percent). 

C.1.b. Percentage of operations by frequency that manure and waste were bedding were 

cleaned from the lambing area during lambing season, and by region:

Percent Operations 

 Region

West Central East

Cleaning frequency Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Between each lambing 18.0 (4.3) 13.9 (2.5) 6.4 (1.5)

Between two or more lambings 14.0 (3.8) 15.3 (2.2) 14.8 (2.2)

At the end of lambing season 27.8 (4.7) 43.1 (3.2) 59.9 (3.1)

Not cleaned 40.2 (5.3) 27.6 (3.2) 18.8 (2.6)

Total 100.0 100.0 100.0

Jugs are small individual pens used to house the ewe-lamb pair shortly after lambing. 

These pens allow the ewe and lamb to bond before being put in with the rest of the fl ock 

and also provide a means for ensuring that the lamb is nursing properly. Over threefourths of operations (79.8 percent) used jugs. This management practice varied little by 

size of operation (data not shown) or by region. 

C.1.c. Percentage of operations that used jugs, by region:

Percent Operations 

Region

West Central East

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

84.0 (3.9) 74.5 (3.2) 82.1 (2.6) 79.8 (1.8)
USDA APHIS VS / 57 

Section I: Population Estimates–C. Lambing Management

For operations that used jugs, 39.2 percent cleaned them between each ewe lambing. 

There was little variation in the cleaning frequency of jugs by fl ock size (data not shown), 

but there were some substantial differences by region. For example, a higher percentage 

of operations in the West region (63.5 percent) cleaned the jugs between each ewe 

lambing compared with operations in the East region (22.7 percent). 

C.1.d. For operations that used jugs, percentage of operations by frequency that manure 

and waste bedding were cleaned from jugs, and by region:

Percent Operations 

 Region

West Central East

All

operations

Cleaning 

frequency Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Between each ewe 63.5 (5.8) 51.7 (3.3) 22.7 (3.1) 39.2 (2.2)

Between two 

or more ewes 18.9 (4.6) 22.5 (2.6) 27.0 (3.3) 24.1 (2.0)

At the end of 

lambing season 9.6 (3.7) 21.1 (2.7) 45.8 (3.6) 31.5 (2.2)

Not cleaned 8.0 (3.4) 4.7 (1.6) 4.6 (1.4) 5.2 (1.1)

Total 100.0 100.0 100.0 100.0
58 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

2. Placenta removal and disposal 

Placentas can harbor infectious organisms and should be removed from the lambing area 

as soon after lambing as possible. Removing placentas is especially important on highdensity operations in which ewes are clustered, making exposure to harmful organisms in 

placentas more likely.

In general, 67.9 percent of operations usually removed placentas from the lambing area. 

A total of 75.3 percent of small operations removed placentas from the lambing area 

compared with 52.9 percent of medium operations and 43.7 percent of large operations. 

C.2.a. Percentage of operations that usually removed placentas from the lambing area, 

by fl ock size:

Percent Operations 

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

75.3 (2.5) 52.9 (3.4) 43.7 (4.9) 67.9 (2.0)

A higher percentage of pasture operations (71.0 percent) removed placentas compared 

with herded/open range operations (42.2 percent). Lambs on herded/open range 

operations are often born on the open range. 

C.2.b. Percentage of operations that usually removed placentas from the lambing area, 

by primary fl ock type:

Percent Operations 

Primary Flock Type 

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

42.2 (8.3) 62.6 (4.6) 71.0 (2.4) 68.1 (6.5)
USDA APHIS VS / 59 

Section I: Population Estimates–C. Lambing Management

Typically, operations that removed placentas removed them within 6 hours of birth. A 

low percentage of operations (4.8 percent) removed the placentas more than 12 hours 

following birth. 

C.2.c. For operations that usually removed placentas from the lambing area, percentage 

of operations by average length of time that placentas were left on the ground before 

removal, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Time left 

on ground (hr) Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Less than 6 77.2 (7.1) 64.2 (5.9) 78.0 (2.7) 85.6 (6.3) 76.0 (2.4)

6–12 14.7 (5.4) 24.3 (5.4) 18.6 (2.6) 14.0 (6.3) 19.2 (2.2)

More than 12 8.1 (4.6) 11.6 (4.0) 3.4 (1.3) 0.4 (0.3) 4.8 (1.2)

Total 100.0 100.0 100.0 100.0 100.0
60 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

Composting and throwing out for carnivores were the two most common methods used 

to dispose of placentas (30.8 and 28.0 percent of operations, respectively). Over half of 

herded/open range operations (51.4 percent) threw out placentas for carnivores; only 

15.7 percent of dry lots left placentas for carnivores. It is not clear that leaving placentas 

for carnivores constitutes purposeful removal. The majority of operations that reported 

“other” as a method of removing placentas tossed the placentas in the manure pile or 

spread the placentas with manure. This method does not truly represent removal, since 

infectious organisms are still spread in the environment and might be consumed by dogs 

or other carnivores.

C.2.d. For operations that usually removed placentas from the lambing area, percentage 

of operations by usual method of placenta disposal, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Burn/incinerate 3.7 (2.3) 10.2 (3.4) 8.5 (1.8) 14.6 (6.4) 9.3 (1.5)

Bury 1.7 (1.4) 4.1 (2.0) 8.3 (1.7) 2.8 (2.7) 6.9 (1.3)

Render 0.0 (—) 0.0 (—) 0.1 (0.1) 0.0 (—) 0.1 (0.1)

Landfi ll/dump 15.4 (5.7) 14.2 (4.2) 15.7 (2.4) 28.0 (7.8) 16.5 (2.0)

Compost 20.9 (6.9) 28.0 (5.1) 31.9 (3.1) 31.0 (7.8) 30.8 (2.5)

Throw out for 

carnivores 51.4 (10.8) 36.3 (5.6) 26.6 (2.9) 15.7 (5.9) 28.0 (2.4)

Other 6.9 (3.6) 7.3 (2.9) 8.9 (1.9) 8.0 (4.8) 8.5 (1.5)

Total 100.0 100.0 100.0 100.0 100.0
USDA APHIS VS / 61 

Section I: Population Estimates–C. Lambing Management

3. Abortion

Overall, 86.8 percent of operations had fi rst-lambing ewes in 2010.

C.3.a. Percentage of operations that had fi rst-lambing ewes, by fl ock type:

Percent Operations 

Primary Flock Type 

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

90.9 (6.6) 87.7 (3.3) 86.7 (1.9) 83.7 (5.2) 86.8 (1.5)

For operations with fi rst-lambing ewes, 60.4 percent had fi rst lambing ewes that aborted, 

while 43.8 percent of all operations had abortions from bred ewes of all age groups. Over 

three-fourths of herded/open range operations (80.5 percent) had any ewes abort in 

2010, while just 42.6 percent of pasture operations had any ewes abort during the same 

period. 

C.3.b. Percentage of operations with one or more ewes that aborted during 2010, by 

primary fl ock type:

Percent Operations1

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Ewe type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

First-lambing2 71.2 (10.2) 45.2 (7.3) 64.7 (4.1) 46.0 (11.2) 60.4 (3.3)

Any 80.5 (10.2) 45.5 (5.5) 42.6 (3.0) 32.9 (7.6) 43.8 (2.4)

1

Only operations in which the last completed lambing season was in 2010.

2

For operations with fi rst lambing ewes. 
62 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

Overall, 1.7 percent of bred ewes aborted during 2010.

C.3.c. Percentage of bred ewes that aborted, by primary fl ock type:

Percent Ewes 

Primary Flock Type 

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

1.9 (0.2) 1.2 (0.2) 1.7 (0.1) 1.6 (0.4) 1.7 (0.1)

First-lambing ewes accounted for just 17.8 percent of bred ewes with full-term births 

(table B.4.e) but 36.7 percent of ewes that aborted. 

C.3.d. For operations that had ewes abort, percentage of all ewes that aborted during 

2010 that were fi rst-lambing ewes, by primary fl ock type:

Percent Ewes 

Primary Flock Type 

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

33.9 (4.8) 40.7 (5.8) 38.3 (3.4) 20.5 (5.8) 36.7 (2.5)
USDA APHIS VS / 63 

Section I: Population Estimates–C. Lambing Management

Most operations (83.5 percent) managed aborting ewes in some way. Over three-fourths 

of operations with ewes that aborted in 2010 (79.6 percent) removed placentas or fetuses 

as soon as possible after the abortion. A higher percentage of pasture and dry lot/feedlot 

operations (82.3 and 94 percent, respectively) removed placentas or fetuses compared 

with herded/open range operations (42.5 percent). Nearly one-third of operations 

(32.6 percent) separated aborting ewes from the rest of the fl ock.

C.3.e. For operations with ewes that aborted during 2010, percentage of operations by 

protocol used for aborting ewes, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Protocol Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Remove placentas 

or fetuses as soon 

as possible

42.5 (8.7) 76.1 (6.3) 82.3 (3.1) 94.0 (4.2) 79.6 (2.5)

Clean the area by 

removing bedding 

and/or dirt

27.2 (8.9) 36.5 (6.8) 27.2 (3.6) 41.0 (10.3) 30.3 (2.9)

Disinfect the area 9.0 (3.6) 15.8 (5.6) 8.3 (2.3) 8.4 (4.0) 9.6 (1.9)

Physically separate 

ewes that aborted 

from other ewes

25.8 (6.1) 36.7 (6.7) 28.4 (3.6) 59.1 (10.3) 32.6 (2.9)

Any of the above 56.1 (9.7) 80.7 (6.1) 85.5 (2.9) 94.0 (4.2) 83.5 (2.4)
64 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

Almost half of operations that separated ewes that had aborted from the rest of the fl ock 

(45.1 percent) kept the ewes out of the fl ock for the rest of the lambing season. 

C.3.f. For operations that physically separated ewes that aborted from the rest of the 

fl ock, percentage of operations by number of days aborting ewes remained separated, 

and by primary fl ock type:

Number of days Percent operations Std. error

1–7 days 19.6 (4.0)

8–30 days 12.4 (3.2)

More than 30 days 7.0 (2.9)

Not returned to fl ock for 

rest of lambing season 45.1 (5.4)

Never returned 

to fl ock 16.0 (3.7)

Total 100.0
USDA APHIS VS / 65 

Section I: Population Estimates–C. Lambing Management

Over one-fourth of operations (26.2 percent) indicated that the cause of abortion during 

2010 was due to one of the causes in the following table. Chlamydiosis was one of the 

most commonly reported causes of abortion (9.0 percent of operations); only 

37.3 percent of these operations had the chlamydiosis diagnosis confi rmed by a 

veterinarian or laboratory. A veterinarian or laboratory confi rmed the cause of less than 

half the abortions attributed to the listed organisms, even though most infectious causes 

of abortion cannot be accurately diagnosed without laboratory evaluation. The majority of 

“other” reported causes of abortion was trauma, usually by predators, but also because of 

shearing stress.

C.3.g. For operations with ewes that aborted during 2010, percentage of operations by 

cause of abortions, and percentage of these operations in which the diagnosis was made 

by a veterinarian or laboratory:

Percent Operations

Abortions in 2010

Cause diagnosed by 

veterinarian or laboratory

Cause Percent Std. error Percent Std. error

Campylobacteriosis 

(vibrio abortion) 6.6 (1.3) 22.6 (6.7)

Chlamydiosis 

(enzootic abortion) 9.0 (1.6) 37.3 (8.9)

Toxoplasmosis 3.4 (1.1) 6.9 (6.5)

Q fever 0.1 (0.1) 0.0 (—)

Salmonellosis 0.1 (0.1) 0.0 (—)

Listeriosis 0.7 (0.3) 0.0 (—)

Cache Valley virus 1.1 (0.5) 43.0 (21.6)

Other 10.3 (1.8) 3.5 (3.3)

Any cause above 26.2 (2.6) 21.6 (4.4)

Unknown 73.8 (2.6) NA

Total 100.0
66 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

Having a dedicated lambing area separate from the sick ewe area reduces the risk of 

disease transmission. Less than one-fi fth of operations (19.3 percent) kept sick ewes in 

the lambing area during the lambing season, while 30.6 percent kept sick ewes in the 

lambing area at times other than the lambing season. There was no measurable variation 

by fl ock type or size.

C.3.h. Percentage of operations that used the lambing area for sick ewes during lambing 

and/or at other times during 2010, by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range

Fenced 

range Pasture

Dry lot/

feedlot

All 

operations

Used . . . Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

During lambing 32.6 (9.0) 22.4 (3.9) 17.4 (1.9) 21.3 (5.4) 19.3 (1.6)

At other times 

of the year 38.1 (9.3) 30.3 (4.4) 29.6 (2.5) 34.3 (6.4) 30.6 (2.0)
USDA APHIS VS / 67 

Section I: Population Estimates–C. Lambing Management

4. Tail docking

Tail docking keeps fecal matter from accumulating on the tail and hindquarters. Fecal 

matter accumulation attracts fl ies, can lead to wool maggots, and potentially reduces pelt 

value. Tail docking is also required for shows, although the required tail length can vary 

by show. Some sheep breeds (e.g., hair sheep, fat-tailed sheep, rat-tailed sheep) do not 

require tail docking. Just over one-tenth of operations did not dock lamb tails. Over half 

the operations docked lambs’ tails at the caudal fold. The caudal fold consists of two fl aps 

of skin under―and attached to each side of―the tail. These fl aps meet in a “V” at the 

end of the caudal fold.

C.4.a. Percentage of operations that docked the tails of lambs born during 2010, by 

location of docking for the majority of lambs’ tails and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Location Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Between the body and 

the caudal fold 26.6 (2.5) 14.3 (2.5) 7.5 (2.0) 22.4 (1.9)

At the “V” of the 

caudal fold 52.1 (2.8) 59.0 (3.4) 58.8 (5.2) 54.2 (2.1)

Distal to 

the caudal fold 9.0 (1.6) 14.3 (2.0) 29.0 (5.0) 11.5 (1.3)

No tail docking 

performed 12.3 (1.9) 12.5 (2.8) 4.7 (3.1) 11.9 (1.5)

Total 100.0 100.0 100.0 100.0
68 / Sheep 2011

Section I: Population Estimates–C. Lambing Management

The percentage of operations that docked tails distal to the caudal fold ranged from 

3.5 percent of operations in the West region to 13.8 percent of operations in the East 

region. 

C.4.b. Percentage of operations that docked the tails of lambs born during 2010, by 

location of docking for the majority of lambs’ tails and by region:

Percent Operations

Region

West Central East

Location Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Between the body and 

the caudal fold 27.8 (5.0) 22.5 (2.9) 20.5 (2.7)

At the “V” of the 

caudal fold 58.3 (5.4) 54.5 (3.3) 52.6 (3.2)

Distal to 

the caudal fold 3.5 (1.1) 12.2 (2.0) 13.8 (2.1)

No tail docking performed 10.4 (3.4) 10.8 (2.6) 13.1 (2.1)

Total 100.0 100.0 100.0

All herded/open range fl ocks docked the tails of their lambs, and over half docked at the 

caudal fold, while nearly one-fourth docked distal to the caudal fold.

C.4.c. Percentage of operations that docked the tails of lambs born during 2010, by 

location of docking for the majority of lambs’ tails and by primary fl ock type:

Percent Operations

Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Location Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Between the body and 

the caudal fold 20.6 (8.3) 21.3 (4.1) 20.7 (2.3) 36.5 (6.9)

At the “V” of the 

caudal fold 54.9 (8.8) 52.5 (4.7) 56.9 (2.7) 38.8 (6.6)

Distal to 

the caudal fold 24.4 (6.8) 12.8 (2.9) 10.3 (1.5) 12.3 (3.7)

No tail docking 

performed 0.0 (0.0) 13.3 (3.7) 12.1 (1.8) 12.4 (5.2)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 69 

Section I: Population Estimates–D. Disease Control and Illness

1. Health management

Sick and injured sheep should be separated from the rest of the fl ock to reduce disease 

transmission, facilitate treatment, and allow injured sheep to heal. A similar percentage 

of operations removed sick sheep and injured sheep from the rest of the fl ock (65.0 and 

64.5 percent, respectively). There was no variation in this practice by fl ock size, region, or 

primary fl ock type.

D.1.a. For operations that had sick or injured sheep, percentage of operations that 

separated sick sheep and percentage that separated injured sheep from the rest of the 

fl ock during 2010, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Sick sheep 69.1 (3.0) 58.5 (3.7) 54.3 (5.3) 65.0 (2.2)

Injured sheep 68.6 (3.2) 55.9 (3.8) 63.4 (5.4) 64.5 (2.4)

For the 65.0 percent of operations that isolated sick sheep, 60.4 percent put them in a 

pen specifi cally for sick animals, although the sick pen was in the same housing area 

used for healthy sheep. “Other” places sick sheep were penned included the lambing pen 

or jug.

D.1.b. For operations that isolated sick sheep during 2010, percentage of operations by 

usual isolation area used for sick sheep, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Isolation area Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

In pen specifi cally 

for sick animals 

but located in the 

same housing as 

other sheep

65.0 (3.8) 52.5 (4.3) 41.7 (6.1) 60.4 (2.9)

In a separate, 

covered structure 26.2 (3.6) 33.6 (4.2) 29.8 (6.8) 28.4 (2.7)

In a separate, 

fenced area 

outside

21.8 (3.4) 27.0 (3.8) 46.1 (6.2) 24.8 (2.5)

Other 3.9 (1.7) 6.4 (2.4) 5.0 (2.0) 4.6 (1.3)

D. Disease 

Control and 

Illness
70 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

For the 65.0 percent of operations that isolated sick sheep during 2010, a higher 

percentage in the East region (69.5 percent) kept sick sheep in a pen specifi cally for sick 

animals compared with operations in the West or Central regions (47.7 and 51.5 percent, 

respectively). A higher percentage of operations in the West region kept sick sheep in a 

separate covered structure (45.2 percent) or separate fenced outside area (41.6 percent) 

compared with operations in the East region ( 21.3 and 16.0 percent, respectively). 

D.1.c. For operations that isolated sick sheep during 2010, percentage of operations by 

usual isolation area used for sick sheep, and by region:

Percent Operations

Region

West Central East

Isolation area Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

In pen specifi cally for sick 

animals but located in the 

same housing as other sheep

47.7 (7.2) 51.5 (5.1) 69.5 (3.8)

In a separate, 

covered structure 45.2 (7.3) 31.4 (5.0) 21.3 (3.3)

In a separate, fenced 

area outside 41.6 (7.3) 31.4 (4.5) 16.0 (3.2)

Other 5.7 (3.1) 7.6 (3.4) 2.8 (1.3)
USDA APHIS VS / 71 

Section I: Population Estimates–D. Disease Control and Illness

For the 65.0 percent of operations that isolated sick sheep during 2010, a higher 

percentage of herded/open range operations (63.6 percent) kept sick sheep in a separate 

fenced outside area compared with pasture and dry lot operations (21.1 and 4.7 percent, 

respectively). 

D.1.d. For operations that isolated sick sheep during 2010, percentage of operations by 

usual isolation area used for sick sheep, and by primary fl ock type:

Percent Operations

Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Isolation area Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

In pen specifi cally 

for sick animals 

but located in the 

same housing as 

other sheep

34.8 (12.5) 53.7 (6.6) 62.3 (3.5) 67.9 (11.5)

In a separate, 

covered structure 32.1 (12.5) 32.4 (6.5) 27.7 (3.3) 25.4 (9.5)

In a separate, 

fenced area 

outside

63.6 (12.2) 37.6 (6.3) 21.1 (3.0) 4.7 (3.4)

Other 5.2 (3.4) 6.7 (3.6) 2.9 (1.0) 19.2 (12.4)
72 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

For the 65.0 percent of operations that isolated sick sheep during 2010, 35.1 percent 

cleaned the area after each sick animal left. Another one-third (32.5 percent) cleaned this 

area seasonally. The majority of large operations either cleaned the area seasonally 

(29.9 percent) or had no set time period to clean the pen (37.1 percent).

D.1.e. For operations that isolated sick sheep during 2010, percentage of operations by 

frequency that isolation area was cleaned, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Cleaning 

frequency Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

After each 

sick animal left 39.1 (3.9) 29.0 (3.9) 16.5 (4.2) 35.1 (2.9)

Weekly 6.3 (2.1) 4.2 (1.6) 8.1 (2.7) 5.9 (1.5)

Monthly 5.1 (1.7) 1.9 (0.9) 8.4 (3.6) 4.5 (1.2)

Seasonally 32.4 (3.8) 33.2 (4.0) 29.9 (6.1) 32.5 (2.8)

No set time 

period to clear 

out the pen

17.1 (2.9) 31.7 (4.2) 37.1 (6.5) 22.0 (2.3)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 73 

Section I: Population Estimates–D. Disease Control and Illness

For the 65.0 percent of operations that isolated sick sheep during 2010, a higher 

percentage of operations in the West region (59.1 percent) cleaned the isolation area 

after each sick animal compared with operations in the East region (26.7 percent). 

D.1.f. For operations that isolated sick sheep during 2010, percentage of operations by 

frequency that isolation area was cleaned, and by region:

Percent Operations

Region

West Central East

Cleaning frequency Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

After each sick animal left 59.1 (6.9) 35.8 (4.9) 26.7 (3.9)

Weekly 3.3 (2.7) 6.3 (2.3) 6.5 (2.4)

Monthly 0.0 (0.0) 6.6 (2.5) 4.8 (1.8)

Seasonally 11.4 (4.4) 30.1 (4.4) 41.0 (4.4)

No set time period to 

clear out the pen 26.2 (5.9) 21.2 (3.9) 21.1 (3.3)

Total 100.0 100.0 100.0
74 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

Pregnant ewes that demonstrate weight loss despite a normal appetite and do not 

respond to treatment are showing signs consistent with scrapie and Johne’s disease 

and may present a risk for disease transmission to the rest of the fl ock, especially at 

lambing. Just over one-tenth of operations (11.1 percent) would cull these animals prior to 

lambing, while 78.9 percent would allow them to lamb and then re-evaluate or cull at that 

time. A higher percentage of large operations than small operations would keep the ewe 

regardless of the signs (23.3 and 8.4 percent, respectively). 

D.1.g. Percentage of operations by the health management practice that best describes 

what would most likely be done if a pregnant ewe demonstrated weight loss despite a 

normal appetite and did not respond to treatment, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Ewe management 

practice Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Cull before lambing 10.5 (1.7) 13.4 (2.4) 8.7 (2.2) 11.1 (1.3)

Allow to lamb, then reevaluate or cull 81.1 (2.3) 75.3 (3.1) 68.0 (5.3) 78.9 (1.8)

Keep regardless 

of the above signs 8.4 (1.6) 11.3 (2.3) 23.3 (5.2) 10.0 (1.5)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 75 

Section I: Population Estimates–D. Disease Control and Illness

A number of infectious diseases can cause ewes to lose weight despite a normal appetite 

and treatment. Since at least one of these—Johne’s disease—can infect lambs in utero, it 

is recommended these ewes be culled before lambing. If not infected in utero, the lambs 

will likely then become infected through the dam’s milk or by ingesting feces from the 

infected dam. A higher percentage of herded/open range operations than fenced range 

operations would, after lambing, re-evaluate or cull ewes that demonstrated weight loss 

despite a normal appetite. 

D.1.h. Percentage of operations by the health management practice that best describes 

what would most likely be done if a pregnant ewe demonstrated weight loss despite a 

normal appetite and did not respond to treatment, and by primary fl ock type:

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot

Ewe management 

practice Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Cull before lambing 3.9 (1.6) 11.6 (3.1) 11.2 (1.7) 12.7 (4.6)

Allow to lamb and then 

re-evaluate or cull 88.9 (3.1) 70.9 (4.3) 80.4 (2.2) 80.4 (5.4)

Keep regardless 

of the above signs 7.3 (2.6) 17.5 (3.6) 8.4 (1.5) 6.9 (3.2)

Total 100.0 100.0 100.0 100.0
76 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

2. Johne’s disease

Johne’s disease is caused by the bacteria Mycobacterium avium subspecies 

paratuberculosis. All ruminant species are susceptible to Johne’s disease, which is 

considered a common infection of cattle, sheep, goats, deer, and bison. There are 

several strains of this organism. While there are strains that primarily infect cattle and 

strains that primarily infect sheep, some cross infections do occur. Therefore, infected 

cattle can pose a risk to sheep. The majority of animals are infected in the fi rst several 

months of life by ingesting bacteria shed in the feces of infected animals. While usually 

infected when young, most sheep do not show clinical signs of Johne’s disease until they 

are 2 to 6 years old. In sheep, the most common sign is losing weight despite a normal 

appetite. Over half of operations (55.9 percent) had either never heard of Johne’s disease 

or had heard the name only.

D.2.a. Percentage of operations by level of familiarity with Johne’s disease, and by fl ock 

size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Level of familiarity Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Very familiar 14.5 (2.1) 12.7 (1.9) 6.5 (1.9) 13.6 (1.5)

Somewhat familiar 29.2 (2.5) 33.5 (3.0) 31.9 (4.9) 30.5 (1.9)

Heard of name only 27.1 (2.5) 32.0 (3.2) 32.7 (4.6) 28.6 (1.9)

Never heard of 29.2 (2.6) 21.8 (2.6) 28.9 (5.1) 27.3 (1.9)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 77 

Section I: Population Estimates–D. Disease Control and Illness

A higher percentage of operations in the East region (19.9 percent) were very familiar 

with Johne’s disease compared with operations in the Central region (6.4 percent). 

D.2.b. Percentage of operations by familiarity with Johne’s disease, and by region:

Percent Operations

Region

West Central East

Level of familiarity Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Very familiar 9.8 (3.3) 6.4 (1.5) 19.9 (2.6)

Somewhat familiar 29.7 (4.8) 20.5 (2.4) 37.7 (3.0)

Heard of name only 32.3 (5.0) 33.7 (3.0) 23.9 (2.9)

Never heard of 28.2 (4.9) 39.4 (3.2) 18.6 (2.7)

Total 100.0 100.0 100.0

For operations very or somewhat familiar with Johne’s disease, 8.8 percent had a fl ock 

health management program specifi cally to control the disease. There was no variation 

by fl ock size. 

D.2.c. For operations very familiar or somewhat familiar with Johne’s disease, 

percentage of operations that had a fl ock health management program specifi cally to 

control or prevent Johne’s disease, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

9.3 (2.4) 7.7 (2.2) 8.6 (3.7) 8.8 (1.8)
78 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

3. Scrapie

Scrapie is a fatal, degenerative disease affecting the central nervous system of sheep 

and goats. Infected fl ocks with a high percentage of susceptible animals can experience 

signifi cant production losses. In these fl ocks, the number of infected animals increases 

over a period of several years, and the age at onset of clinical signs decreases, making 

these fl ocks economically unviable. Animals sold from infected fl ocks can spread scrapie 

to other fl ocks. The presence of scrapie in the United States also prevents the export 

of breeding stock, semen, and embryos to many other countries. Scrapie is part of an 

eradication program in the United States. For more information, visit 

www.eradicatescrapie.org. 

Overall, 84.8 percent of operations were either very or somewhat familiar with scrapie. 

There was no substantial variation by fl ock type (data not shown). 

D.3.a. Percentage of operations by level of familiarity with scrapie, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Level of familiarity Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Very familiar 43.1 (2.8) 40.1 (3.0) 31.6 (4.5) 41.6 (2.1)

Somewhat familiar 42.0 (2.8) 42.9 (3.2) 58.6 (5.1) 43.2 (2.1)

Heard of name only 12.7 (1.9) 15.9 (2.8) 9.3 (3.4) 13.3 (1.5)

Never heard of 2.3 (0.9) 1.2 (0.9) 0.5 (0.4) 1.9 (0.7)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 79 

Section I: Population Estimates–D. Disease Control and Illness

A higher percentage of operations in the Central region had heard of scrapie by name 

only or had never heard of scrapie compared with operations in the West and East 

regions.

D.3.b. Percentage of operations by familiarity with scrapie and by region:

Percent Operations

Region

West Central East

Level of familiarity Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Very familiar 51.0 (5.4) 36.9 (3.2) 41.8 (3.1)

Somewhat familiar 43.9 (5.3) 36.7 (3.1) 47.5 (3.2)

Heard of name only 4.5 (2.1) 21.1 (3.0) 10.7 (2.1)

Never heard of 0.6 (0.4) 5.3 (1.8) 0.0 (—)

Total 100.0 100.0 100.0

Nearly half of operations very or somewhat familiar with scrapie (47.3 percent) 

implemented genetic selection to control scrapie in their fl ock. There was no substantial 

variation by size or by region.

D.3.c. For operations very familiar or somewhat familiar with scrapie, percentage of 

operations that implemented genetic selection to control scrapie in their fl ock, by fl ock 

size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

48.3 (3.1) 47.6 (3.3) 35.7 (4.2) 47.3 (2.3)
80 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

For the 47.3 percent of operations that implemented genetic selection, 98.8 percent 

used replacement rams genetically resistant to scrapie (RR alleles). A lower percentage 

of large operations (22.7 percent) selected genetically less susceptible ewes compared 

with small operations (53.2 percent). The majority of “other” methods for genetic selection 

were to keep a closed fl ock. There was no variation by region (data not shown). 

D.3.d. For operations that genetically selected for scrapie control and were very familiar

or somewhat familiar with scrapie, percentage of operations by genetic selection 

practices currently being used for scrapie control, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Selection practice Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Use genetically 

less susceptible 

replacement rams 

(i.e., RR alleles)

98.5 (1.0) 99.5 (0.5) 100.0 (—) 98.8 (0.7)

Select genetically less 

susceptible ewes (i.e., 

QR or RR alleles)

53.2 (4.5) 40.7 (4.9) 22.7 (5.5) 48.6 (3.4)

Cull genetically more 

susceptible ewes (i.e., 

QQ alleles)

32.1 (4.2) 18.4 (4.2) 11.4 (4.0) 27.8 (3.1)

Other 1.7 (1.2) 4.6 (2.2) 0.0 (—) 2.3 (1.0)

4. Ovine progressive pneumonia

Ovine Progressive Pneumonia (OPP) is a slowly progressive viral disease of adult 

sheep caused by an ovine lentivirus. Most sheep do not show clinical signs of OPP, but 

the sheep that do typically do not display signs until 2 years of age or older because of 

the virus’s long incubation period. Often, the fi rst sign noticed is a general loss of body 

condition referred to as “thin ewe syndrome.” Weight loss occurs despite the affected 

sheep having normal appetites. Another common sign of OPP is increased breathing 

effort at rest; animals tire easily and may be seen trailing the fl ock. These sheep are often 

called “lungers.” Secondary bacterial infection is very common and results in additional 

signs such as fever, cough, lethargy, and nasal discharge. OPP infection also can cause 

“hard bag,” an enlarged, fi rm udder with reduced or no milk fl ow. Infection with OPP 

virus also may cause other problems such as meningitis and encephalitis. Clinical signs 

include an unsteady gait, twitching, or stumbling, which can progress to hind limbs or 

total paralysis. Arthritis may accompany OPP infection. Pain and swelling of the joints and 

a shortened gait are common. 
USDA APHIS VS / 81 

Section I: Population Estimates–D. Disease Control and Illness

Once infected, animals remain infected for life, though many will never show clinical signs 

of disease. Flocks infected with OPP can have lowered production effi ciency because of 

early culling, decreased milk production, and lower weaning weights.

Just over half of all operations (53.5 percent) were very or somewhat familiar with ovine 

progressive pneumonia (OPP). 

D.4.a. Percentage of operations by familiarity with OPP and by region:

Percent Operations

Region

West Central East

All

operations

Level of familiarity Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Very familiar 15.0 (3.9) 14.9 (2.1) 15.9 (2.2) 15.4 (1.5)

Somewhat familiar 39.7 (5.4) 35.3 (3.2) 39.6 (3.1) 38.1 (2.1)

Heard of name only 23.8 (4.7) 20.2 (2.6) 19.5 (2.6) 20.4 (1.8)

Never heard of 21.5 (4.5) 29.6 (3.3) 25.0 (2.8) 26.0 (1.9)

Total 100.0 100.0 100.0 100.0

Of operations very or somewhat familiar with OPP, 16.2 percent had a fl ock health 

management program specifi cally to control or prevent OPP. 

D.4.b. For operations very or somewhat familiar with OPP, percentage of operations 

that had a fl ock health management program specifi cally to control or prevent OPP, by 

region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

24.5 (6.5) 16.2 (2.9) 13.4 (2.7) 16.2 (2.0)
82 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

Over half of operations that had a fl ock health management program for OPP removed all 

seropositive sheep and lambs from the fl ock (52.6 percent) or kept the fl ock isolated from 

infected sheep or goats (55.8 percent). 

D.4.c. For operations that had a fl ock health management program for OPP, percentage 

of operations by method used to control or prevent OPP:

Method Percent operations Std. error

Remove all seropositive sheep 

and lambs from fl ock (sold and/or 

isolated in separate facilities)

52.6 (6.8)

Keep fl ock isolated from 

infected sheep or goats 55.8 (6.7)

Add only seronegative sheep to fl ock 42.3 (8.3)

Add only sheep from 

OPP-seronegative fl ocks 42.7 (8.2)

Test goats (if present) for 

caprine arthritis encephalitis 21.9 (9.7)

Other method 25.9 (5.6)

Nearly three-fourths of operations (72.7 percent) did not know their current OPP status. 

The lowest percentage of operations known to be currently infected with OPP was in the 

West region (0.7 percent). 

D.4.d. Percentage of operations by current OPP status of fl ock, and by region:

Percent Operations

Region

West Central East

All

operations

Flock status Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Currently infected 

with OPP 0.7 (0.4) 7.8 (1.8) 5.4 (1.6) 5.4 (1.0)

Previously infected with 

OPP but now negative 3.7 (2.6) 4.4 (1.8) 2.3 (1.1) 3.3 (0.9)

Never infected with OPP 25.6 (6.6) 9.4 (2.7) 22.4 (3.8) 18.7 (2.4)

Do not know 

current OPP status 70.1 (6.8) 78.4 (3.5) 69.9 (4.0) 72.7 (2.6)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 83 

Section I: Population Estimates–D. Disease Control and Illness

5. Toxoplasmosis and coxiellosis 

Toxoplasmosis and coxiellosis (Q fever) can cause abortion storms, yet 28.5 percent of 

sheep producers had not heard of toxoplasmosis, and 52.0 percent had not heard of 

Q fever.

D.5. Percentage of operations by level of familiarity with toxoplasmosis and Q fever:

Percent Operations

Level of Familiarity

Very Somewhat

Heard of 

name only

Never 

heard of

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Total

Toxoplasmosis 15.1 (1.6) 30.9 (1.9) 25.5 (1.9) 28.5 (2.0) 100.0

Q fever 4.0 (0.9) 13.2 (1.4) 30.8 (2.0) 52.0 (2.2) 100.0

0 20 40 60

Coxiellosis (Q fever)

Toxoplasmosis

OPP

Scrapie

Johne's disease
84 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

6. Diseases present in the last 3 years

The four most commonly seen diseases in the previous 3 years were sore mouth 

(43.7 percent of operations), footrot (37.3 percent), enterotoxemia/overeating disease 

(35.0 percent), and coccidiosis (34.0 percent). Scrapie was suspected on only 

1.7 percent of participating operations during the previous 3 years. Of this 1.7 percent, 

70.4 percent indicated that scrapie diagnosis was made by a veterinarian or laboratory. 

Some of these operations may have reported that scrapie had been suspected on their 

operation because their sheep were exposed to scrapie-positive or high-risk animals; 

however, their sheep may not have been infected.

D.6. Percentage of operations by disease present in the last 3 years, and percentage of 

these operations in which disease was diagnosed by a veterinarian or laboratory: 

Disease

Percent 

operations 

with disease

Std. 

error

Percent in 

which disease 

diagnosed by 

veterinarian 

or laboratory

Std. 

error

Johne’s 

(paratuberculosis) 2.5 (0.6) 40.8 (12.7)

Scrapie 1.7 (0.6) 70.4 (19.6)

Ovine progressive 

pneumonia (OPP) 8.2 (0.9) 24.6 (4.6)

Footrot 37.3 (2.1) 8.4 (1.9)

Caseous lymphadenitis 

(lumpy jaw) 24.5 (1.9) 24.1 (3.8)

Enterotoxemia/

overeating disease 

(Clostridium perfringens

type C&D) 

(not grain overload)

35.0 (1.9) 19.7 (2.7)

Other clostridial diseases 

(e.g., blackleg, malignant 

edema, braxy, tetanus, 

botulism, big head)

10.4 (1.2) 17.7 (4.2)

Coccidiosis 34.0 (2.0) 37.0 (3.5)

Sore mouth 

(contagious ecthyma, orf) 43.7 (2.1) 12.2 (2.1)

Ring worm or 

club lamb fungus 8.9 (1.3) 18.8 (6.5)

Bluetongue 3.6 (0.7) 19.6 (9.5)
USDA APHIS VS / 85 

Section I: Population Estimates–D. Disease Control and Illness

7. Vaccination practices

Because they can reduce the prevalence or severity of disease, vaccines are an integral 

part of any fl ock management program. Whether an operation should use particular 

vaccines, however, depends on whether the fl ock is open or closed, the geographic 

region of the country, diet, soil type, age of the sheep, and previous disease problems. 

Overall, 81.6 percent of operations vaccinated their sheep or lambs in 2010. There was 

no substantial variation by size, region, or fl ock type (data not shown).

D.7.a. Percentage of operations that vaccinated any sheep or lambs during 2010, by 

fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

80.3 (2.4) 83.1 (2.9) 89.5 (3.5) 81.6 (1.8)

D.7.b. Percentage of operations that vaccinated any sheep or lambs during 2010, by 

region:

Percent Operations

Region

West Central East

Percent Std. error Percent Std. error Percent Std. error

87.6 (3.6) 76.9 (3.2) 82.7 (2.6)
86 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

The two vaccines used by the highest percentage of operations were enterotoxemia 

(71.4 percent) and tetanus (64.5 percent). The Footvax® vaccine was used to control 

footrot but was discontinued for sale in the United Stated in 2011. Since then, there have 

been efforts by the U.S. sheep industry to have the vaccine approved for limited sale and 

distribution. 

D.7.c. For operations with the specifi ed sheep type, percentage of operations by type of 

vaccine given and by type of sheep vaccinated during 2010: 

Percent Operations

Sheep Type

Nursing 

lambs

Weaned 

feeder 

(market)

lambs

Weaned 

replacement 

lambs Ewes Rams Any

Vaccine type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Clostridial

7- or 8-way 

(e.g., blackleg, 

malignant edema) 

19.2 (1.7) 12.7 (1.5) 15.3 (1.5) 20.5 (1.7) 14.8 (1.5) 29.5 (1.9)

C. perfringens

C and D 

(enterotoxemia, 

overeating)

60.5 (2.1) 39.8 (2.2) 37.9 (2.1) 38.8 (2.1) 28.8 (1.9) 71.4 (2.0)

C. tetani (tetanus) 55.0 (2.1) 32.9 (2.1) 33.0 (2.1) 34.0 (2.0) 25.3 (1.9) 64.5 (2.1)

Respiratory

IBR-PI-3 1.9 (0.5) 0.6 (0.3) 0.6 (0.3) 0.0 (—) NA 2.7 (0.6)

Pneumonia

(Pasteurella/

Mannheimia)

0.8 (0.3) 0.6 (0.3) 0.8 (0.3) 1.5 (0.5) 0.5 (0.2) 2.1 (0.5)

Digestive

Scours (E. coli) 0.3 (0.2) 0.8 (0.4) 0.3 (0.2) 0.3 (0.2) NA 0.9 (0.4)

Rotavirus NA NA 0.0 (0.0) 0.0 (0.0) NA 0.0 (0.0)
USDA APHIS VS / 87 

Section I: Population Estimates–D. Disease Control and Illness

D.7.c. (cont’d.) For operations with the specifi ed sheep type, percentage of operations by 

type of vaccine given and by type of sheep vaccinated during 2010: 

Percent Operations

Sheep Type

Nursing 

lambs

Weaned 

feeder 

(market)

lambs

Weaned 

replacement 

lambs Ewes Rams Any

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Reproductive

Ram epididymitis 

bacterin (Brucella) NA NA NA NA 0.0 (0.0) NA

EAE 

(Chlamydiophila 

abortus)

NA NA 5.7 (1.0) 7.6 (1.1) NA 8.1 (1.1)

Leptospirosis NA NA 2.9 (0.7) 4.1 (0.9) NA 4.2 (0.9)

Campylobacter 

fetus/jejuni (vibrio) NA NA 10.7 (1.2) 14.6 (1.4) NA 15.2 (1.4)

Other

Lumpy jaw 

(caseous 

lymphadenitis)

1.5 (0.6) 0.8 (0.4) 2.0 (0.6) 2.4 (0.7) 2.5 (0.7) 3.4 (0.8)

Footrot 0.3 (0.2) 0.1 (0.1) 1.1 (0.4) 3.4 (0.8) 2.0 (0.6) 3.5 (0.8)

Rabies 0.0 (—) 0.1 (0.1) 0.6 (0.3) 1.1 (0.5) 1.1 (0.5) 1.2 (0.5)

Sore mouth 

(contagious 

ecthyma)

8.1 (1.0) 2.7 (0.7) 4.3 (0.9) 1.5 (0.6) 0.9 (0.4) 11.0 (1.2)
88 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

0 20 40 60 80
USDA APHIS VS / 89 

Section I: Population Estimates–D. Disease Control and Illness

Of the 15.2 percent of operations that vaccinated for Campylobacter fetus/jejuni (vibrio) 

(table D.7.c), most used the Colorado Serum Company vaccine.

D.7.d. For operations that vaccinated for Campylobacter fetus/jejuni (vibrio) in weaned 

replacement lambs and ewes, percentage of operations by vaccine type used:

Percent Operations

Weaned

replacement lambs Ewes

Vaccine type Percent Std. error Percent Std. error

Colorado Serum Co. 61.0 (5.9) 61.6 (5.0)

Hygienia Biological Labs 24.8 (5.6) 19.4 (4.3)

Both 0.7 (0.7) 0.0 (—)

Don’t know 13.6 (3.6) 19.0 (3.9)
90 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

Because the sore mouth vaccine is comprised of live virus, vaccinating against sore 

mouth is only recommended when a fl ock is already infected with the virus. Vaccinating a 

fl ock can introduce the infection to a fl ock not already infected. 

Of the 11.0 percent of operations that vaccinated any sheep for sore mouth, 70.6 percent 

used a commercially available vaccine and 5.9 percent used an autogenous vaccine from 

a veterinarian. While 11.1 percent of operations in the Central region used an autogenous 

sore mouth vaccine, none of the operations in the West and East regions did. In the East 

region, 21.6 percent of operations did not know which sore mouth vaccine was used. 

D.7.e. Percentage of operations that vaccinated any sheep* for sore mouth during 2010, 

and for those operations, percentage of operations by type of vaccine most recently 

used, and by region:

Percent Operations

Region

West Central East

All 

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Vaccinated any 

sheep for sore 

mouth

21.2 (4.3) 16.7 (2.0) 3.5 (1.4) 11.0 (1.2)

Vaccine

Colorado Serum 

Company 88.6 (7.6) 57.6 (6.6) 78.4 (18.2) 70.6 (5.4)

Autogenous vaccine 

from veterinarian 0.0 (—) 11.1 (4.7) 0.0 (—) 5.9 (2.6)

Other 10.4 (7.5) 24.3 (6.2) 0.0 (—) 16.0 (4.2)

Do not know 1.0 (0.9) 7.0 (3.2) 21.6 (18.2) 7.5 (3.7)

Total 100.0 100.0 100.0 100.0

*Nursing lambs, weaned feeder (market) lambs, weaned replacement lambs, ewes, or rams.
USDA APHIS VS / 91 

Section I: Population Estimates–D. Disease Control and Illness

When the sore mouth vaccine was given, the owner/operator gave the vaccine on 

86.2 percent of operations. Gloves help to protect hands from accidental exposure to live 

virus and were worn more frequently when the owner/operator gave the vaccine 

(45.4 percent of operations) than when a farm worker gave the vaccine (13.1 percent).

D.7.f. For operations that vaccinated any sheep* for sore mouth during 2010, percentage 

of operations by who administered the vaccine, and percentage of these operations by 

whether gloves were worn while vaccinating: 

Percent Operations

Gave vaccine Gloves worn

Person administering vaccine Percent Std. error Percent Std. error

Veterinarian 0.0 (—) NA

Farm worker(s) 29.0 (5.6) 13.1 (3.5)

Owner/operator 86.2 (4.4) 45.4 (6.2)

*Nursing lambs, weaned feeder (market) lambs, weaned replacement lambs, ewes, or rams.

As mentioned previously, the Footvax vaccine was not available for sale in the United 

States at the time of this study. If it had been, 26.2 percent of operations indicated they 

would have used it. This percentage did not vary substantially by fl ock size, region, or 

primary fl ock type (data not shown). 

D.7.g. Percentage of operations that would use Footvax vaccine if it were available, by 

fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

24.3 (2.7) 30.9 (3.1) 27.2 (3.7) 26.2 (2.0)
92 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

8. Market lamb injections

Note: In this section, “weaned market lambs” refers to lambs intended for market and 

weaned while still on the operation. It does not include lambs that were weaned at the 

time of transport. 

The majority of operations (79.3 percent) had weaned lambs intended for market during 

2010. 

D.8.a. Percentage of operations with weaned lambs intended for market during 2010, by 

fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

78.8 (2.2) 84.1 (2.3) 65.3 (4.9) 79.3 (1.7)

A higher percentage of operations in the East region (89.3 percent) had weaned lambs 

intended for market during 2010 compared with the operations in the Central region 

(65.7 percent).

D.8.b. Percentage of operations with weaned lambs intended for market during 2010, by 

region:

Percent Operations

Region

West Central East

Percent Std. error Percent Std. error Percent Std. error

77.9 (4.2) 65.7 (3.2) 89.3 (2.0)
USDA APHIS VS / 93 

Section I: Population Estimates–D. Disease Control and Illness

A lower percentage of herded/open range operations (51.9 percent) had weaned market 

lambs compared with pasture operations (85.1 percent). This result is likely because 

many herded/open range operations wean their market lambs as they leave the operation 

and these lambs are not included in this section. 

D.8.c. Percentage of operations with weaned lambs intended for market during 2010, by 

primary fl ock type:

Percent Operations 

Primary Flock Type 

Herded/

open range Fenced range Pasture Dry lot/feedlot 

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

51.9 (8.8) 64.9 (4.6) 85.1 (1.9) 80.3 (5.9)

Injections are administered to market lambs for a variety of reasons, including 

vaccination, antibiotic treatment for disease, and manipulation of the reproductive cycle. 

Although injection-site lesions are not a food safety issue, scar tissue at the injection 

site can affect meat quality. Therefore, it is generally recommended that all injections be 

given in the neck. Over one-third of operations with weaned lambs (37.9 percent) gave 

no injections to their weaned market lambs, while nearly half (48.7 percent) gave one to 

two injections to each of their market lambs. There was no substantial difference by fl ock 

size.

D.8.d. For operations with weaned market lambs, percentage of operations by number of 

injections of any kind given to weaned market lambs during 2010, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Number of 

injections Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

0 37.3 (3.2) 38.2 (3.8) 44.7 (6.9) 37.9 (2.4)

1–2 47.2 (3.2) 53.9 (3.8) 41.9 (6.7) 48.7 (2.4)

3–4 14.3 (2.3) 6.8 (1.5) 9.0 (2.9) 12.1 (1.7)

5 or more 1.3 (0.7) 1.1 (0.6) 4.4 (2.1) 1.4 (0.5)

Total 100.0 100.0 100.0 100.0
94 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

No operations in the East region gave fi ve or more injections of any kind to their weaned 

market lambs, but 3.8 percent of operations in the West region and 2.8 percent in the 

Central region did. 

D.8.e. For operations with weaned market lambs, percentage of operations by number of 

injections of any kind given to weaned market lambs during 2010, and by region:

Percent Operations

Region

West Central East

Number of injections Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

0 38.6 (6.0) 42.7 (4.0) 35.3 (3.4)

1–2 39.7 (5.9) 46.9 (3.9) 52.1 (3.5)

3–4 17.8 (4.9) 7.6 (1.9) 12.6 (2.4)

5 or more 3.8 (2.1) 2.8 (1.5) 0.0 (—)

Total 100.0 100.0 100.0

A higher percentage of herded/open range operations (70.2 percent) gave no injections 

to their weaned market lambs compared with fenced range (39.6 percent), pasture 

(37.1 percent), and dry lot/feedlot (35.5 percent) operations. A low percentage of 

herded/open range (3.9 percent), fenced range (3.4 percent), and pasture (1.0 percent) 

operations gave fi ve or more injections to their weaned market lambs. 

D.8.f. For operations with weaned market lambs, percentage of operations by number of 

injections of any kind given to weaned market lambs during 2010, and by primary fl ock 

type:

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot 

Number of 

injections Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

0 70.2 (8.8) 39.6 (5.7) 37.1 (2.9) 35.5 (7.8)

1–2 25.9 (8.0) 50.3 (5.9) 49.0 (3.0) 48.5 (7.8)

3–4 0.0 (—) 6.8 (2.7) 12.9 (2.1) 16.0 (5.9)

5 or more 3.9 (3.6) 3.4 (2.4) 1.0 (0.5) 0.0 (—)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 95 

Section I: Population Estimates–D. Disease Control and Illness

Nearly all injections given to weaned market lambs were administered by farm personnel. 

There was very little difference across fl ock sizes, regions, or fl ock types in the 

percentage of operations by person administering injections (data not shown). 

D.8.g. For operations that gave injections of any kind to weaned market lambs 

during 2010, operation average percentage of all injections administered, by person 

administering injections and by fl ock size:

Operation Average Percent Injections 

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Person 

administering 

injection Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error

Farm personnel 99.6 (0.4) 96.4 (1.3) 100.0 (0.0) 98.8 (0.4)

Veterinarian 0.1 (0.1) 2.4 (1.0) 0.0 (—) 0.7 (0.3)

Other 0.4 (0.4) 1.2 (0.8) 0.0 (—) 0.6 (0.3)

Total 100.0 100.0 100.0 100.0

Approximately three-fourths of injections given to weaned market lambs (76.7 percent) 

were given subcutaneously (SQ). Virtually no injections were given intravenously (IV). 

There were no substantial differences in injection route by region or fl ock type (data not 

shown). 

D.8.h. For operations that gave injections of any kind to weaned market lambs during 

2010, operation average percentage of all injections given, by injection route and by fl ock 

size:

Operation Average Percent Injections

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Injection route Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error Avg.

Std. 

error

Intramuscular (IM) 17.7 (3.8) 16.7 (4.0) 30.7 (15.0) 23.3 (7.3)

Subcutaneous (SQ) 82.3 (3.8) 83.3 (4.0) 69.3 (15.0) 76.7 (7.3)

Intravenous (IV) 0.0 (—) 0.0 (0.0) 0.0 (—) 0.0 (0.0)

Total 100.0 100.0 100.0 100.0
96 / Sheep 2011

Section I: Population Estimates–D. Disease Control and Illness

Of the 23.3 percent of operations that gave intramuscular (IM) injections (table D.8.h), 

over half (58.1 percent) gave IM injections in the neck, while 38.6 percent gave IM 

injections in the leg. Nearly all large operations (95.8 percent) gave IM injections in the 

neck compared with only 49.3 percent of small operations. Only 4.2 percent of large 

operations gave IM injections in the leg compared with 47.7 percent of small operations. 

D.8.i. For operations that gave IM injections of any kind to weaned market lambs during 

2010, percentage of operations by primary location of injection and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

IM injection 

location Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Neck 49.3 (8.3) 69.4 (10.0) 95.8 (3.8) 58.1 (6.4)

Loin 0.0 (—) 0.0 (—) 0.0 (—) 0.0 (—)

Leg 47.7 (8.4) 26.3 (9.8) 4.2 (3.8) 38.6 (6.4)

Other location 3.1 (3.0) 4.3 (3.1) 0.0 (—) 3.3 (2.1)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 97 

Section I: Population Estimates–E. Antibiotics

1. Antibiotic use

Overall, 69.0 percent of operations administered oral, injectable, or topical antibiotics 

to lambs or ewes to treat any disease during 2010; 59.0 percent of operations gave 

antibiotics to ewes, and 15.7 percent gave antibiotics to weaned market lambs. 

E.1.a. For operations with the specifi ed sheep type, percentage of operations that 

administered antibiotics* to treat any disease during 2010, by fl ock size: 

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Nursing lambs 40.9 (2.7) 48.1 (3.0) 48.8 (4.6) 43.1 (2.1)

Weaned 

replacement 

lambs

17.8 (2.2) 21.1 (2.5) 20.5 (4.2) 18.8 (1.7)

Weaned 

market lambs 13.4 (1.9) 21.6 (2.4) 18.3 (3.1) 15.7 (1.4)

Ewes 56.4 (2.8) 64.7 (3.4) 65.4 (5.1) 59.0 (2.1)

Any 67.2 (2.7) 73.5 (3.2) 70.5 (5.2) 69.0 (2.1)

*Oral, injectable, or topical.

E. Antibiotics
98 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

Weaned market lambs were administered oral, injectable, or topical antibiotics by 

9.5 percent of operations in the Central region and by 19.6 percent of operations in the 

West region.

E.1.b. For operations with the specifi ed sheep type, percentage of operations that 

administered antibiotics* to treat any disease during 2010 by region: 

Percent Operations

Region

West Central East

Sheep type Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Nursing lambs 44.4 (5.4) 38.6 (2.8) 45.9 (3.2)

Weaned replacement lambs 24.2 (4.7) 15.7 (2.4) 19.2 (2.5)

Weaned market lambs 19.6 (4.5) 9.5 (1.7) 18.8 (2.2)

Ewes 66.5 (5.2) 50.3 (3.2) 62.6 (3.2)

Any 73.6 (4.9) 62.1 (3.3) 72.2 (3.0)

*Oral, injectable, or topical.

A lower percentage of herded/open range and fenced range operations (5.8 and 

5.7 percent, respectively) administered oral, injectable, or topical antibiotics to market 

lambs to treat disease compared with pasture operations (18.4 percent).

E.1.c. For operations with the specifi ed sheep type, percentage of operations that 

administered antibiotics* to treat any disease during 2010 by primary fl ock type: 

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot 

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Nursing lambs 34.9 (6.3) 33.5 (4.1) 47.2 (2.6) 36.7 (6.4)

Weaned 

replacement lambs 9.7 (3.1) 14.3 (3.3) 19.7 (2.1) 22.1 (5.6)

Weaned 

market lambs 5.8 (2.3) 5.7 (1.9) 18.4 (1.9) 22.0 (5.5)

Ewes 53.3 (8.5) 49.7 (4.6) 63.4 (2.7) 49.4 (6.9)

Any 53.3 (8.5) 58.1 (4.7) 73.8 (2.5) 63.7 (7.0)

*Oral, injectable, or topical.
USDA APHIS VS / 99 

Section I: Population Estimates–E. Antibiotics

2. Antibiotic treatment records

An essential part of responsible antibiotic use is record keeping. At a minimum, these 

records should note the antibiotic name, animals treated, date treated, and reason for 

treatment. Just over half of all operations that administered antibiotics (51.0 percent) 

kept any records of antibiotic use. Overall, the highest percentage of operations that 

administered antibiotics (45.8 percent) kept records on the identity of animals treated. 

Knowing what animals were treated helps ensure an adequate withdrawal time before 

an animal is sent to slaughter, or before its milk is used for human consumption. A higher 

percentage of small operations kept records for name of product, identity of animals 

treated, and reason for treatment compared with large operations. There were no 

substantial differences in record-keeping practices by region (data not shown).

E.2.a. For operations that administered antibiotics* to lambs or ewes during 2010, 

percentage of operations by type of antibiotic treatment records kept, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Record type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Product 

expiration date 17.1 (2.6) 15.0 (2.8) 16.7 (3.3) 16.5 (1.9)

Name of product 38.1 (3.2) 34.5 (3.4) 23.2 (3.9) 36.2 (2.4)

Identity of 

animals treated 49.3 (3.3) 41.1 (3.5) 27.9 (4.2) 45.8 (2.4)

Reason for 

treatment 41.0 (3.3) 32.2 (3.4) 18.2 (3.6) 37.3 (2.4)

Any record 53.5 (3.2) 47.4 (3.6) 38.3 (4.4) 51.0 (2.4)

*Oral, injectable, or topical.
100 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

Herded/open range operations accounted for the lowest percentage of operations that 

kept antibiotic-use records of any kind (27.6 percent). 

E.2.b. For operations that administered antibiotics* to lambs or ewes during 2010, 

percentage of operations by type of antibiotic treatment records kept and by primary fl ock 

type:

Percent Operations 

 Primary Flock Type

Herded/

open range Fenced range Pasture

Dry lot/

feedlot 

Record type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Product 

expiration date 13.1 (4.4) 15.3 (4.3) 16.4 (2.3) 22.7 (7.6)

Name of product 18.0 (4.8) 29.9 (5.2) 36.7 (2.9) 47.3 (8.1)

Identity of 

animals treated 21.1 (5.5) 43.3 (5.7) 45.1 (3.0) 61.1 (7.6)

Reason for 

treatment 9.8 (4.0) 34.3 (5.6) 37.3 (2.9) 48.4 (8.0)

Any record 27.6 (5.8) 51.2 (5.7) 49.8 (3.0) 63.6 (7.4)

*Oral, injectable, or topical.
USDA APHIS VS / 101 

Section I: Population Estimates–E. Antibiotics

3. Antibiotics given1

For the 69.0 percent of operations that gave any antibiotics (table E.1.a), respiratory 

disease was the most common illness treated with antibiotics (67.7 percent of 

operations). The antibiotic class used most frequently to treat respiratory disease 

was penicillin, followed by tetracycline, and phenicol (29.9, 19.2, and 13.6 percent of 

operations that gave any antibiotics, respectively). 

Mastitis, lameness, and diarrhea/scours or other digestive disorder were the next most 

frequently treated diseases or disorders (44.2, 35.8, and 30.4 percent of operations that 

gave any antibiotics, respectively). The antibiotic used most frequently to treat mastitis 

was penicillin (26.1 percent of operations) while the most frequently used antibiotic to 

treat for lameness was tetracycline (22.2 percent). Aminoglycosides were used more 

frequently than any other antibiotic to treat diarrhea/scours or other digestive disorder 

(12.6 percent). 

Few drugs are approved for use in sheep, thus many of the drugs listed below are being 

used under the Animal Medicinal Drug Use Clarifi cation Act (AMDUCA), which requires a 

valid veterinary-client-patient relationship; such use is considered to be extra-label. While 

currently allowed under AMDUCA, aminoglycoside use is generally discouraged due to 

its prolonged persistence in tissues.

1

See appendix III for antibiotic classes and active ingredients.
102 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

E.3. For operations that gave any antibiotics* (excluding preventive treatments) to 

individual lambs or ewes during 2010, percentage of operations by antibiotic given and by 

disease or disorder treated: 

Percent Operations

Disease or Disorder

Respiratory

Diarrhea/

scours 

or other 

digestive Pinkeye

Navel 

infection

Lameness/

footrot

Antibiotic class Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.1 (0.1) 12.6 (1.7) 0.4 (0.2) 0.1 (0.1) 0.2 (0.2)

Penicillin 29.9 (2.4) 4.0 (0.9) 1.6 (0.6) 7.6 (1.2) 8.1 (1.4)

Cephalosporin 4.4 (1.0) 1.1 (0.5) 0.2 (0.2) 0.9 (0.4) 1.1 (0.6)

Phenicol 

(i.e., fl orfenicol) 13.6 (1.8) 1.1 (0.5) 0.0 (—) 0.4 (0.3) 3.8 (1.2)

Lincosamide 0.3 (0.3) 0.0 (—) 0.0 (—) 0.1 (0.1) 0.0 (0.0)

Macrolide 4.5 (1.0) 0.0 (—) 0.0 (—) 0.1 (0.1) 0.5 (0.4)

Sulfonamide 1.0 (0.5) 7.9 (1.4) 0.0 (0.0) 0.0 (—) 0.0 (0.0)

Tetracycline 19.2 (1.8) 5.7 (1.0) 7.2 (1.3) 2.0 (0.5) 22.2 (2.0)

Other 3.4 (1.0) 1.4 (0.6) 3.8 (1.0) 0.5 (0.4) 0.7 (0.5)

Any 67.7 (2.5) 30.4 (2.3) 13.2 (1.8) 11.8 (1.4) 35.8 (2.5)

*Oral, injectable, or topical.
USDA APHIS VS / 103 

Section I: Population Estimates–E. Antibiotics

E.3. (con’t.) For operations that gave any antibiotics* (excluding preventive treatments) to 

individual lambs or ewes during 2010, percentage of operations by antibiotic given and by 

disease or disorder treated: 

Percent Operations

Disease or Disorder

Reproductive Mastitis Abortion Other

Antibiotic Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.1 (0.1) 0.4 (0.3) 0.0 (—) 0.0 (—)

Penicillin 13.2 (1.7) 26.1 (2.2) 4.1 (1.0) 8.2 (1.5)

Cephalosporin 0.7 (0.4) 3.3 (0.8) 0.1 (0.1) 0.4 (0.2)

Phenicol 

(i.e., fl orfenicol) 0.8 (0.5) 2.4 (0.8) 0.4 (0.3) 1.5 (0.6)

Lincosamide 0.0 (—) 0.6 (0.3) 0.1 (0.1) 0.0 (—)

Macrolide 0.1 (0.1) 1.6 (0.6) 0.0 (—) 0.3 (0.3)

Sulfonamide 0.6 (0.2) 0.3 (0.1) 0.1 (0.1) 0.0 (—)

Tetracycline 3.7 (0.8) 9.1 (1.4) 3.9 (0.8) 4.3 (1.1)

Other 0.4 (0.4) 0.6 (0.6) 0.0 (—) 0.3 (0.3)

Any 19.7 (1.9) 44.2 (2.5) 8.7 (1.3) 14.2 (1.8)

*Oral, injectable, or topical.
104 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

4. Treatment of nursing lambs

One-third of operations with nursing lambs (33.8 percent) treated them for respiratory 

disease. About half that many (18.6 percent) treated nursing lambs for diarrhea/scours or 

other digestive problem. The use of antibiotics to treat navel infections increased as fl ock 

size increased.

E.4.a. For operations with nursing lambs, percentage of operations that gave nursing 

lambs any antibiotics* to treat the following diseases disorders, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Disease/disorder Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Respiratory 31.0 (2.6) 37.8 (3.0) 40.6 (4.4) 33.8 (2.0)

Diarrhea/scours 

or other digestive 

problem

17.1 (2.0) 21.6 (2.4) 23.8 (3.5) 18.6 (1.5)

Pinkeye 2.3 (0.8) 3.2 (1.0) 5.3 (1.8) 2.7 (0.6)

Navel infection 4.5 (1.2) 15.3 (2.0) 19.0 (3.3) 8.1 (1.0)

Other 3.9 (1.0) 2.9 (0.9) 2.4 (1.1) 3.5 (0.7)

Any 40.9 (2.7) 48.1 (3.0) 48.8 (4.6) 43.1 (2.1)

*Oral, injectable, or topical.
USDA APHIS VS / 105 

Section I: Population Estimates–E. Antibiotics

Of the 43.1 percent of operations that treated nursing lambs with antibiotics during 2010 

(table E.1.a), 43.6 percent treated for respiratory disease using penicillin. Penicillin was 

also used most commonly to treat navel infection in nursing lambs (64.9 percent of 

operations). Aminoglycosides were used by 43.9 percent of operations to treat diarrhea/

scours or other digestive problem, while tetracycline was used most commonly to treat 

pinkeye (43.5 percent of operations). The majority of “other” antibiotics used to treat 

pinkeye were a tetracycline/peptide class compound.

E.4.b. For operations that treated nursing lambs with antibiotics* during 2010, percentage 

of operations by antibiotic given, and by disease or disorder treated:

Percent Operations

Disease or Disorder

Respiratory

Diarrhea/ 

scours 

or other 

digestive Pinkeye

Navel 

infection Other

Antibiotic Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.0 (—) 43.9 (4.7) 9.3 (5.6) 0.7 (0.7) 0.0 (—)

Penicillin 43.6 (3.5) 11.1 (2.9) 12.6 (5.8) 64.9 (5.9) 59.1 (10.2)

Cephalosporin 5.5 (1.4) 2.9 (1.5) 0.0 (—) 8.0 (3.4) 0.0 (—)

Phenicol 

(i.e., fl orfenicol) 19.7 (2.9) 3.7 (1.8) 0.0 (—) 3.1 (2.7) 11.2 (6.9)

Lincosamide 0.0 (—) 0.0 (—) 0.0 (—) 1.2 (1.1) 0.0 (—)

Macrolide 4.7 (1.6) 0.0 (—) 0.0 (—) 0.9 (0.8) 6.6 (6.3)

Sulfonamide 1.5 (0.9) 19.7 (4.0) 1.1 (1.0) 0.0 (—) 0.0 (—)

Tetracycline 20.3 (2.5) 15.3 (2.9) 43.5 (11.8) 16.9 (4.1) 16.7 (6.2)

Other 4.7 (1.7) 3.3 (1.6) 33.5 (10.5) 4.2 (3.1) 6.4 (4.7)

*Oral, injectable, or topical.
106 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

Not all sick animals on operations that used antibiotics were treated. For example, on the 

43.1 percent of operations that treated nursing lambs with antibiotics (table E.1.a), 

2.8 percent of nursing lambs had respiratory disease; of these lambs, 93.9 percent were 

treated. Therefore, 2.6 percent of nursing lambs on operations that used oral, injectable, 

or topical antibiotics were treated for respiratory disease. While 3.5 percent of nursing 

lambs on operations that used oral, injectable, or topical antibiotics had diarrhea/scours 

or other digestive problems, just 82.2 percent of those lambs were treated. Therefore, 

2.9 percent of all nursing lambs on operations that used oral, injectable, or topical 

antibiotics were treated for diarrhea/scours or other digestive problem. 

E.4.c. For operations that treated nursing lambs with antibiotics1 during 2010, percentage 

of nursing lambs affected by disease, and percentage of affected lambs treated, by 

disease/disorder treated:

Percent Nursing Lambs2

Disease/disorder Affected

Std. 

error

Of those 

affected, 

percent 

treated

Std. 

error

Respiratory 2.8 (0.3) 93.9 (2.1)

Diarrhea/scours 

or other digestive 

problem

3.5 (0.6) 82.2 (10.0)

Pinkeye 0.2 (0.1) 97.0 (2.2)

Navel infection 0.4 (0.1) 95.8 (1.6)

Other 0.7 (0.5) 98.7 (1.3)

1

 Oral, injectable, or topical.

2

 As a percentage of lambs born in 2011.
USDA APHIS VS / 107 

Section I: Population Estimates–E. Antibiotics

5. Treatment of weaned replacement lambs

Overall, 12.0 percent of operations with weaned replacement lambs treated them for 

respiratory disease. A lower percentage of operations treated weaned replacement lambs 

for diarrhea/scours or other digestive problem (5.1 percent), lameness (3.8 percent), or 

pinkeye (1.8 percent). There was no variation by fl ock size or region (data not shown).

E.5.a. For operations with weaned replacement lambs, percentage of operations that 

gave weaned replacement lambs any antibiotics* to treat the following diseases or 

disorders, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Disease/disorder Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Respiratory 10.8 (1.8) 14.7 (2.0) 14.9 (4.0) 12.0 (1.4)

Diarrhea/scours 

or other digestive 

problem

5.4 (1.3) 4.4 (1.6) 5.1 (3.3) 5.1 (1.0)

Pinkeye 1.7 (0.7) 1.2 (0.6) 4.8 (3.2) 1.8 (0.5)

Lameness 3.3 (1.0) 4.8 (1.2) 4.9 (1.9) 3.8 (0.7)

Other 2.4 (0.9) 0.3 (0.3) 0.6 (0.5) 1.8 (0.6)

Any 17.8 (2.2) 21.1 (2.5) 20.5 (4.2) 18.8 (1.7)

*Oral, injectable, or topical antibiotics.
108 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

Of the 18.8 percent of operations that gave antibiotics to weaned replacement lambs 

(table E.1.a), 29.8 percent treated weaned replacement lambs with phenicol for 

respiratory disease. Tetracycline was used to treat a broad spectrum of diseases. The 

majority of “other” antibiotics used to treat pinkeye were a tetracycline/peptide class 

compound.

E.5.b. For operations that treated weaned replacement lambs with antibiotics* during 

2010, percentage of operations by antibiotic given, and by disease or disorder treated:

Percent Operations

Disease or Disorder

Respiratory

Diarrhea/ 

scours 

or other 

digestive Pinkeye

Lameness/ 

footrot Other

Antibiotic Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.0 (—) 27.0 (9.9) 0.0 (—) 1.6 (1.5) 0.0 (—)

Penicillin 24.1 (5.4) 12.3 (6.6) 5.4 (3.7) 19.7 (8.5) 50.2 (18.2)

Cephalosporin 7.1 (2.8) 5.4 (5.2) 0.0 (—) 6.6 (6.2) 5.5 (5.4)

Phenicol (i.e., 

fl orfenicol) 29.8 (5.4) 7.1 (5.3) 0.0 (—) 4.0 (3.8) 23.6 (13.6)

Lincosamide 0.0 (—) 0.0 (—) 0.0 (—) 0.0 (—) 0.0 (—)

Macrolide 9.3 (4.1) 0.0 (—) 0.0 (—) 6.7 (6.3) 0.0 (—)

Sulfonamide 0.3 (0.2) 36.8 (10.1) 0.0 (—) 0.0 (—) 0.0 (—)

Tetracycline 24.2 (4.9) 11.3 (5.9) 29.6 (14.8) 54.8 (10.0) 20.7 (13.6)

Other 5.2 (2.4) 0.0 (—) 65.0 (15.7) 6.6 (6.2) 0.0 (—)

*Oral, injectable, or topical antibiotics.
USDA APHIS VS / 109 

Section I: Population Estimates–E. Antibiotics

Not all of the operations that used antibiotics treated all sick weaned replacement lambs. 

For example, on the 18.8 percent of operations that administered antibiotics to weaned 

replacement lambs (table E1.a), 1.2 percent of lambs had respiratory disease and, of 

these lambs, 93.5 percent were treated with antibiotics. Therefore, 1.1 percent of all 

weaned replacement lambs on these operations were treated for respiratory disease 

during 2010.

E.5.c. For operations that treated weaned replacement lambs with antibiotics1 during 

2010, percentage of weaned replacement lambs affected by disease, and percentage of 

affected lambs treated, by disease/disorder treated:

Percent Weaned Replacement Lambs2

Disease/disorder Affected

Std. 

error

Of those 

affected, 

percent 

treated

Std. 

error

Respiratory 1.2 (0.2) 93.5 (3.4)

Diarrhea/scours 

or other digestive 

problem

0.6 (0.2) 90.7 (5.9)

Pinkeye 0.3 (0.1) 98.8 (1.2)

Lameness 1.1 (0.5) 98.8 (1.0)

Other 0.2 (0.1) 97.8 (2.2)

1

 Oral, injectable, or topical.

2

 As a percentage of lambs born in 2010.
110 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

6. Treatment of weaned market lambs

Overall, 11.2 percent of operations with weaned market lambs treated the lambs for 

respiratory disease. In comparison, a lower percentage of these operations treated 

weaned market lambs for diarrhea/scours or other digestive problem (5.1 percent), 

lameness (3.8 percent), or pinkeye (1.1 percent). 

E.6.a. For operations with weaned market lambs, percentage of operations that gave 

weaned market lambs any antibiotics* to treat the following diseases or disorders, by 

fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Disease/disorder Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Respiratory 9.2 (1.6) 15.6 (2.0) 16.4 (3.0) 11.2 (1.2)

Diarrhea/scours 

or other digestive 

problem

5.7 (1.3) 4.1 (1.2) 2.6 (1.1) 5.1 (1.0)

Pinkeye 0.9 (0.5) 1.6 (1.2) 2.4 (1.1) 1.1 (0.5)

Lameness/footrot 2.9 (0.9) 6.4 (1.4) 3.9 (1.6) 3.8 (0.7)

Other 0.8 (0.4) 0.9 (0.5) 1.1 (0.6) 0.9 (0.3)

Any 13.4 (1.9) 21.6 (2.4) 18.3 (3.1) 15.7 (1.4)

*Oral, injectable, or topical.
USDA APHIS VS / 111 

Section I: Population Estimates–E. Antibiotics

Of the 15.7 percent of operations that treated weaned market lambs with antibiotics 

(table E.1.a), most used tetracycline to treat pinkeye and lameness (62.2 and 

59.3 percent of operations, respectively). The treatment for respiratory disease varied, 

with 31.4 percent of operations using fl orphenicol, 25.8 percent of operations using 

tetracycline, and 22.8 percent of operations using penicillin. The treatment for diarrhea/

scours or other digestive problem was even more split, with sulfonamide, aminoglycoside, 

tetracycline, cephalosporin, and penicillin all used to some extent. The majority of “other” 

antibiotics used to treat pinkeye were a tetracycline/peptide class compound.

E.6.b. For operations that treated weaned market lambs with antibiotics* during 2010, 

percentage of operations by antibiotic given, and by disease or disorder treated:

Percent Operations

Disease or Disorder

Respiratory

Diarrhea/ 

scours 

or other 

digestive Pinkeye

Lameness/ 

footrot Other

Antibiotic Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.0 (—) 20.1 (8.6) 0.0 (—) 0.0 (—) 0.0 (—)

Penicillin 22.8 (4.8) 12.1 (6.5) 7.5 (5.6) 17.6 (7.6) 18.3 (12.5)

Cephalosporin 9.4 (3.6) 13.3 (7.3) 0.0 (—) 11.9 (7.5) 11.5 (10.8)

Phenicol 

(i.e., fl orfenicol) 31.4 (5.5) 1.7 (1.0) 0.0 (—) 3.5 (2.2) 22.7 (14.4)

Lincosamide 0.0 (—) 0.0 (—) 0.0 (—) 0.0 (—) 0.0 (—)

Macrolide 6.8 (2.9) 0.0 (—) 0.0 (—) 0.9 (0.8) 0.0 (—)

Sulfonamide 0.3 (0.3) 27.9 (8.6) 0.0 (—) 0.8 (0.7) 0.0 (—)

Tetracycline 25.8 (4.6) 18.9 (7.9) 62.2 (23.8) 59.3 (9.5) 47.4 (19.9)

Other 3.5 (2.2) 9.0 (5.6) 30.3 (23.9) 6.0 (5.6) 0.0 (—)

*Oral, injectable, or topical antibiotics.
112 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

Not all operations that used antibiotics treated all sick animals. For example, on the 

15.7 percent of operations that administered antibiotics to weaned market lambs (table 

E.1.a), 11.0 percent of weaned market lambs were lame or had footrot, and 81.4 percent 

of affected lambs were treated. Therefore, 8.9 percent of all weaned market lambs on 

these operations were treated for lameness or footrot.

E.6.c. For operations that treated weaned market lambs with antibiotics1 during 2010, 

percentage of lambs affected by the following diseases:

Percent Weaned Market Lambs2

Disease/disorder Affected

Std. 

error

Of those 

affected, 

percent 

treated

Std. 

error

Respiratory 6.0 (1.3) 92.5 (3.4)

Diarrhea/scours 

or other digestive 

problem

5.3 (2.1) 78.8 (8.7)

Pinkeye 1.1 (0.7) 83.6 (13.3)

Lameness/footrot 11.0 (3.5) 81.4 (7.5)

Other 0.7 (0.3) 74.5 (14.9)

1

 Oral, injectable, or topical.

2

 As a percentage of weaned market lambs on January 1, 2011.
USDA APHIS VS / 113 

Section I: Population Estimates–E. Antibiotics

7. Treatment of ewes

About one-fourth of all operations treated ewes for respiratory disease and lameness 

(24.6 and 24.4 percent, respectively). There were no substantial differences by region 

(data not shown).

E.7.a. For operations with ewes, percentage of operations that gave ewes any antibiotics* 

to treat the following diseases or disorders, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Disease/disorder Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Respiratory 23.2 (2.3) 25.0 (2.5) 39.0 (4.3) 24.6 (1.7)

Diarrhea/scours 

or other digestive 

problem

4.0 (1.0) 1.8 (0.8) 3.4 (1.3) 3.4 (0.8)

Pinkeye 6.6 (1.4) 6.5 (1.9) 8.3 (2.1) 6.6 (1.1)

Lameness/footrot 21.5 (2.3) 31.2 (2.8) 29.6 (3.7) 24.4 (1.8)

Reproductive 11.0 (1.7) 14.6 (2.0) 23.0 (3.4) 12.6 (1.3)

Mastitis 27.3 (2.4) 37.2 (3.2) 41.3 (4.8) 30.6 (1.9)

Abortion 4.6 (1.1) 7.8 (1.5) 13.6 (3.0) 5.9 (0.9)

Other 6.4 (1.4) 4.1 (1.1) 5.5 (2.0) 5.8 (1.0)

Any 56.4 (2.8) 64.7 (3.4) 65.4 (5.1) 59.0 (2.1)

*Oral, injectable, or topical.
114 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

On the 59.0 percent of operations that treated ewes with antibiotics (table E.1.a), 

tetracycline was the most commonly used antibiotic to treat pinkeye and lameness 

(60.5 and 61.5 percent of operations, respectively). Just over two-thirds of operations 

(67.1 percent) that treated ewes with antibiotics used penicillin to treat for reproductive 

disease. Sulfonamide was rarely used for any condition other than diarrhea/scours or 

other digestive disorder. The majority of “other” antibiotics used to treat pinkeye were a 

tetracycline/peptide class compound.

E.7.b. For operations that treated ewes with antibiotics* during 2010, percentage of 

operations by antibiotic given, and by disease or disorder treated:

Percent Operations

Disease or Disorder

Respiratory

Diarrhea/

scours or other 

digestive Pinkeye

Lameness/

footrot

Antibiotic Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.2 (0.2) 11.8 (7.7) 0.0 (—) 0.6 (0.4)

Penicillin 38.8 (4.0) 19.9 (9.5) 10.1 (5.7) 21.4 (3.5)

Cephalosporin 5.0 (2.1) 3.6 (3.4) 0.4 (0.3) 2.0 (1.3)

Phenicol 

(i.e., fl orfenicol) 14.6 (2.9) 3.6 (3.5) 0.0 (—) 11.0 (3.1)

Lincosamide 0.8 (0.8) 0.0 (—) 0.0 (—) 0.1 (0.1)

Macrolide 3.5 (1.2) 0.0 (—) 0.0 (—) 1.3 (1.0)

Sulfonamide 0.5 (0.4) 41.6 (12.4) 0.5 (0.4) 0.0 (—)

Tetracycline 33.2 (3.6) 19.6 (9.2) 60.5 (8.8) 61.5 (4.2)

Other 3.2 (1.2) 0.0 (—) 28.5 (7.8) 2.0 (1.3)

*Oral, injectable, or topical.
USDA APHIS VS / 115 

Section I: Population Estimates–E. Antibiotics

E.7.b. (cont’d.) For operations that treated ewes with antibiotics* during 2010, percentage 

of operations by antibiotic given, and by disease or disorder treated:

Percent Operations

Disease or Disorder

Reproductive Mastitis Abortion Other

Antibiotic Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Aminoglycoside 0.5 (0.5) 0.9 (0.7) 0.0 (—) 0.0 (—)

Penicillin 67.1 (4.9) 59.0 (3.6) 47.1 (7.8) 55.4 (9.1)

Cephalosporin 3.8 (2.0) 7.4 (1.9) 1.2 (1.2) 3.0 (2.1)

Phenicol 

(i.e., fl orfenicol) 3.9 (2.4) 5.4 (1.7) 4.5 (3.8) 8.1 (5.4)

Lincosamide 0.0 (—) 1.2 (0.7) 1.2 (1.2) 0.0 (—)

Macrolide 0.7 (0.7) 3.5 (1.4) 0.0 (—) 0.0 (—)

Sulfonamide 3.0 (1.2) 0.6 (0.3) 1.4 (1.3) 0.0 (—)

Tetracycline 18.8 (3.8) 20.6 (3.1) 44.5 (7.6) 33.5 (8.7)

Other 2.2 (1.9) 1.4 (1.3) 0.0 (—) 0.0 (—)

*Oral, injectable, or topical.
116 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

Not all operations that used antibiotics treated all sick animals. For example, on the 

59.0 percent of operations that administered antibiotics to ewes (table E.1.a), 1.5 percent 

of ewes had respiratory disease and, of these ewes, 96.0 percent were treated with 

antibiotics. Therefore, 1.4 percent of ewes on operations that used oral, injectable, or 

topical antibiotics during 2010 were treated for respiratory disease. 

E.7.c. For operations that treated ewes with antibiotics1 during 2010, percentage of 

ewes affected by disease, and percentage of affected ewes treated, by disease/disorder 

treated:

Percent Ewes2

Disease/disorder Affected

Std. 

error

Of those 

affected, 

percent treated

Std. 

error

Respiratory 1.5 (0.2) 96.0 (1.7)

Diarrhea/scours 

or other digestive 0.4 (0.1) 74.6 (13.8)

Pinkeye 0.6 (0.2) 95.6 (2.3)

Lameness/footrot 3.9 (0.5) 89.7 (3.4)

Reproductive 0.7 (0.1) 96.6 (1.4)

Mastitis 1.4 (0.1) 89.0 (2.7)

Abortion 0.7 (0.2) 74.6 (8.4)

Other 0.3 (0.1) 94.7 (2.4)

1

Oral, injectable, or topical.

2

As a percentage of ewe inventory on January 1, 2011.
USDA APHIS VS / 117 

Section I: Population Estimates–E. Antibiotics

8. Coccidiostats and growth promotants 

Subclinical coccidiosis in lambs is often responsible for signifi cant reduction in weight 

gain. Therefore, coccidiostats are generally considered cost effective. Overall, 

39.8 percent of operations used a coccidiostat in feed or water. The most commonly 

used coccidiostat used was ionophores in feed (21.9 percent of operations). A higher 

percentage of small and medium operations (21.8 and 25.5 percent, respectively) used 

ionophores in feed during 2011 compared with large operations (8.1 percent). 

E.8.a. Percentage of operations that used coccidiostats in feed or water during 2010, by 

coccidiostat used and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Coccidiostat Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Feed

Ionophores 21.8 (2.4) 25.5 (2.6) 8.1 (3.4) 21.9 (1.8)

Sulfa drugs 1.4 (0.7) 1.3 (0.7) 1.1 (1.0) 1.4 (0.5)

Decoquinate 14.8 (2.0) 16.7 (2.1) 14.2 (2.7) 15.2 (1.5)

Amprolium 2.7 (1.0) 1.9 (0.7) 1.2 (0.8) 2.4 (0.7)

Other 0.3 (0.3) 0.0 (—) 0.0 (—) 0.2 (0.2)

Water

Sulfa drugs 6.9 (1.4) 3.9 (1.0) 2.7 (1.2) 5.9 (1.0)

Decoquinate 0.3 (0.2) 1.1 (0.9) 1.5 (1.0) 0.6 (0.3)

Amprolium 11.3 (1.8) 11.5 (2.0) 7.5 (2.4) 11.1 (1.4)

Other 0.0 (—) 0.3 (0.3) 0.0 (—) 0.1 (0.1)

Any coccidiostat 

in feed or water 40.0 (2.7) 41.9 (2.9) 29.1 (4.4) 39.8 (2.0)
118 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

A higher percentage of operations in the East region (55.5 percent) used coccidiostats 

in feed or water compared with operations in the West or Central regions (30.9 and 

21.6 percent, respectively). A higher percentage of operations in the East region used 

ionophores or decoquinate in feed (31.8 and 21.0 percent, respectively) compared with 

operations in the West region (14.7 and 9.4 percent, respectively) or the Central region 

(11.4 and 10.0 percent, respectively). Very few operations in the Central and East regions 

(0.6 and 0.7 percent, respectively) used decoquinate in water, and virtually no operations 

in the West region did. 

E.8.b. Percentage of operations that used coccidiostats in feed or water during 2010, by 

coccidiostat used and by region:

Percent Operations

Region

West Central East

Coccidiostat Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Feed

Ionophores 14.7 (3.9) 11.4 (1.8) 31.8 (3.1)

Sulfa drugs 0.4 (0.4) 0.7 (0.4) 2.1 (1.1)

Decoquinate 9.4 (3.3) 10.0 (1.7) 21.0 (2.5)

Amprolium 0.6 (0.4) 1.2 (0.5) 3.9 (1.3)

Other 0.0 (0.0) 0.5 (0.5) 0.0 (0.0)

Water

Sulfa drugs 5.2 (2.5) 1.4 (0.6) 9.4 (1.9)

Decoquinate 0.0 (0.0) 0.6 (0.4) 0.7 (0.5)

Amprolium 8.3 (3.0) 5.0 (1.1) 16.4 (2.4)

Other 0.0 (0.0) 0.0 (0.0) 0.1 (0.1)

Any coccidiostat 

in feed or water 30.9 (5.1) 21.6 (2.3) 55.5 (3.1)
USDA APHIS VS / 119 

Section I: Population Estimates–E. Antibiotics

Overall, 20.8 percent of operations used any growth promotant in feed or water. A total 

of 12.5 percent of operations used aureomycin premix or soluble powder in feed as a 

growth promotant, and 4.8 percent used tetracycline. Only 1.1 percent of operations used 

tetracycline in water. 

E.8.c. Percentage of operations that used a growth promotant in feed or water during 

2010, by growth promotant used and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Growth 

promotant Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Feed

Aureomycin 

premix or soluble 

powder 

12.2 (1.8) 12.3 (2.0) 15.9 (3.2) 12.5 (1.4)

Tetracycline 4.3 (1.0) 5.2 (1.3) 9.3 (2.4) 4.8 (0.8)

Neomycin 

sulfate 0.3 (0.3) 0.4 (0.4) 0.0 (—) 0.3 (0.2)

Other antibiotics 0.0 (—) 0.4 (0.4) 0.0 (—) 0.1 (0.1)

Ionophores 10.3 (1.8) 16.5 (2.1) 5.0 (1.8) 11.5 (1.3)

Water

Aureomycin 

premix or soluble 

powder 

0.0 (—) 0.4 (0.4) 1.4 (0.9) 0.2 (0.1)

Tetracycline 1.2 (0.7) 0.7 (0.5) 2.0 (1.1) 1.1 (0.5)

Neomycin 

sulfate 0.0 (—) 0.2 (0.2) 0.0 (—) 0.0 (0.0)

Other antibiotics 0.3 (0.3) 0.4 (0.4) 0.0 (—) 0.3 (0.3)

Any growth 

promotant in 

feed or water

19.4 (2.2) 24.1 (2.4) 23.4 (3.6) 20.8 (1.7)
120 / Sheep 2011

Section I: Population Estimates–E. Antibiotics

A higher percentage of operations in the East and Central regions (26.5 and 

18.5 percent, respectively) gave any growth promotants in feed or water compared with 

operations in the West region (8.3 percent). Very few operations in the East region used 

either neomycin sulfate (0.7 percent) or other antibiotics (0.2 percent) in feed, while no 

operations in the West or Central regions used either in feed. 

E.8.d. Percentage of operations that used a growth promotant in feed or water during 

2010, by growth promotant used and by region:

Percent Operations

Region

West Central East

Growth promotant Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Feed

Aureomycin premix 

or soluble powder 4.9 (2.3) 8.7 (1.5) 17.6 (2.4)

Tetracycline 1.9 (1.5) 6.1 (1.2) 4.8 (1.3)

Neomycin sulfate 0.0 (—) 0.0 (—) 0.7 (0.5)

Other antibiotics 0.0 (—) 0.0 (—) 0.2 (0.2)

Ionophores 3.9 (1.8) 7.6 (1.6) 16.7 (2.4)

Water

Aureomycin premix 

or soluble powder 0.0 (—) 0.2 (0.2) 0.2 (0.2)

Tetracycline 1.0 (0.6) 1.2 (1.1) 1.1 (0.6)

Neomycin sulfate 0.0 (—) 0.1 (0.1) 0.0 (—)

Other antibiotics 0.0 (—) 0.0 (—) 0.7 (0.5)

Any growth promotant 

in feed or water 8.3 (2.7) 18.5 (2.3) 26.5 (2.8)
USDA APHIS VS / 121 

Section I: Population Estimates–F. Parasites and Deworming

In sheep, internal parasites commonly live in the abomasum and the small and large 

intestines, where they damage the mucosa and, depending on the worm species, feed 

on blood, leading to reduced weight gain, weight loss, and death. Parasites are a major 

limiting factor to sheep production on pastures located in moist and warm climates. 

Sheep raised on herded/open range, or even fenced range in dry climates, will not 

normally develop a heavy parasite burden. In more intensive grazing systems, controlling 

gastrointestinal parasites is critical; however, controlling parasites is becoming more 

diffi cult as resistance to dewormers becomes more frequent. 

Fecal egg counts are commonly used to diagnose parasite species and quantify the 

amount of gastrointestinal parasites present in the fl ock. Egg counts can also be used 

to determine which sheep always have high egg counts and, therefore, should probably 

be culled. Fecal egg counts are also valuable in determining whether anthelminthic 

resistance is present in the fl ock. The presence of worms does not necessarily indicate 

that deworming is required. Sheep should be dewormed strategically, based on a 

number of indicators including timing (prelambing), clinical signs, and pasture movement. 

Deworming should never be used alone as a control strategy. More information on when 

to deworm sheep can be found at: www.acsrpc.org.

1. Fecal testing

A higher percentage of operations in the East region (19.8 percent) performed fecal 

testing for intestinal parasites compared with operations in the Central region 

(9.9 percent). 

F.1.a. Percentage of operations that performed fecal testing for intestinal parasites during 

2010, by region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std. 

error Pct.

Std.

error

17.3 (4.0) 9.9 (1.8) 19.8 (2.5) 16.0 (1.5)

F. Parasites and 

Deworming
122 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

Very few herded/open range operations (4.4 percent) performed fecal testing for intestinal 

parasites during 2010 compared with fenced range (14.8 percent) or pasture 

(18.0 percent) operations. 

F.1.b. Percentage of operations that performed fecal testing for intestinal parasites during 

2010, by primary fl ock type: 

Percent Operations

Primary Flock Type

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std.

error Pct.

Std.

error Pct.

Std. 

error Pct.

Std.

error

4.4 (1.9) 14.8 (3.0) 18.0 (2.0) 7.9 (3.5)

2. Deworming

The majority of operations never used dewormers in sheep feed for stomach or intestinal 

worms during 2010. There were no substantial differences by region, fl ock size, or fl ock 

type (data not shown). 

F.2.a. Percentage of operations by frequency dewormers were used in sheep feed for 

stomach or intestinal worms (not including coccidia) during 2010, and by region:

Percent Operations

Region

West Central East

All

operations

Frequency Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Always 7.9 (3.1) 3.9 (1.5) 3.4 (1.2) 4.3 (0.9)

Sometimes 4.9 (2.0) 5.6 (1.7) 10.9 (1.9) 8.1 (1.2)

Never 87.2 (3.6) 90.5 (2.2) 85.8 (2.2) 87.6 (1.4)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 123 

Section I: Population Estimates–F. Parasites and Deworming

The majority of operations (89.2 percent) used an oral (not in feed) or injectable 

dewormer in 2010. A lower percentage of operations in the Central region (78.4 percent) 

used oral or injectable dewormers compared with operations in the West or East regions 

(90.8 and 96.2 percent, respectively). 

F.2.b. Percentage of operations that used a dewormer given orally (not in feed) or by 

injection during 2010, by region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

90.8 (3.0) 78.4 (2.7) 96.2 (1.3) 89.2 (1.3)

The percentage of operations that used oral or injectable dewormers during 2010 ranged 

from 49.0 percent of herded/open range operations to 93.3 percent of pasture operations.

F.2.c. Percentage of operations that used a dewormer given orally (not in feed) or by 

injection during 2010, by primary fl ock type:

Percent Operations

Primary Flock Type

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

49.0 (8.6) 84.5 (3.2) 93.3 (1.4) 86.2 (4.9)
124 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

Ewes and lambs were dewormed as a general preventive measure by the highest 

percentage of operations (87.3 and 78.8 percent, respectively). 

F.2.d. For operations that used a dewormer given orally (not in feed) or by injection in 

ewes and lambs during 2010, percentage of operations by reason for administering 

dewormer:

Percent Operations

Dewormer Used in . . .

Ewes Lambs

Reason Percent Std. error Percent Std. error

General preventive measure 87.3 (1.6) 78.8 (2.0)

Because worms were seen 21.3 (2.0) 23.9 (2.1)

Fecal test results 

indicated a need 11.0 (1.3) 11.5 (1.5)

Because sheep or lambs 

were thin or doing poorly 48.0 (2.3) 44.0 (2.4)

Bottlejaw, scours, and 

other clinical signs 38.9 (2.2) 33.6 (2.3)

Other 2.0 (0.6) 2.2 (0.7)

The FAMACHA© card originated in South Africa and has been validated by the Southern 

Consortium for Small Ruminant Parasite Control as a very effective method for controlling 

the intestinal parasite Haemonchus contortus, or barber’s pole worm, so named because 

of its blood-fi lled intestines spiraling around its white egg-fi lled uterus. Barber’s pole 

worms are arguably one of the most economically important parasites for sheep and 

goat producers. They live in the animal’s intestines and feed on blood from the host, 

sometimes causing anemia, bottle jaw (swelling under the jaw), or death. Barber’s pole 

worms can also damage the nutrition-absorbing cells of the intestines, causing weight 

loss, poor growth, and reduced milk production. 

Young lambs are most sensitive to Haemonchus, while older lambs and sheep usually 

acquire some immunity to the parasite. Not all lambs or sheep become clinically ill with 

severe anemia. Animals with minimal or no anemia do not need to be treated for worms. 

In fact, treating all sheep for worms can contribute to the development of resistance 

to dewormers. Dewormer resistance is a serious concern for the sheep and other 

animal industries. The FAMACHA card allows producers to identify which sheep need 

to be treated for barber’s pole worms and which do not. The card provides a chart with 

examples of inner eyelid color and allows a producer to compare sheep eyelid color with 

the chart to determine whether anemia exists and, therefore, which animals need to be 
USDA APHIS VS / 125 

Section I: Population Estimates–F. Parasites and Deworming

treated for worms. However, it is important to note that anemia can be caused by many 

things other than the barber’s pole worm. Therefore, if deworming does not improve the 

animal’s condition, then some other illness might be present. Sheep that always need 

to be treated may need to be evaluated for culling, and good record keeping will help 

identify these animals. 

Just over one-tenth of operations (11.3 percent) used the FAMACHA card/eye color 

anemia score for sheep or lambs. 

F.2.e. Percentage of operations that used the FAMACHA card/eye color (anemia) score 

for sheep or lambs, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

11.1 (1.8) 12.6 (2.1) 8.5 (3.5) 11.3 (1.4)

A higher percentage of pasture operations (14.4 percent) used the FAMACHA card 

compared with fenced range (5.3 percent) or herded/open range (0.0 percent) operations. 

F.2.f. Percentage of operations that used the FAMACHA card/eye color (anemia) score 

for sheep or lambs, by primary fl ock type:

Percent Operations

Primary Flock Type

Herded/

open range Fenced range Pasture Dry lot/feedlot

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

0.0 (—) 5.3 (2.3) 14.4 (1.9) 7.4 (3.6)
126 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

A higher percentage of operations in the East region (17.5 percent) used the FAMACHA 

card than operations in the Central region (3.2 percent).

F.2.g. Percentage of operations that used the FAMACHA card/eye color (anemia) score 

for sheep or lambs, by region: 

Percent Operations

Region

West Central East

Percent Std. error Percent Std. error Percent Std. error

9.6 (3.3) 3.2 (1.1) 17.5 (2.4)

Of the 11.3 percent of operations that used the FAMACHA card system in 2010 

(table F.2.e), 81.9 percent used it to selectively deworm sheep or lambs. The majority of 

“other” reasons for using the FAMACHA card was as a learning tool.

F.2.h. For operations that used the FAMACHA card/eye color (anemia) score for sheep or 

lambs, percentage of operations by reason for using the FAMACHA card:

Reason Percent operations Std. error

Identify or cull worm-susceptible 

sheep or lambs 60.6 (6.4)

Selectively deworm sheep or 

lambs (e.g., only sheep or lambs 

with certain scores 

were dewormed)

81.9 (5.1)

Other 10.5 (3.8)
USDA APHIS VS / 127 

Section I: Population Estimates–F. Parasites and Deworming

A higher percentage of operations dewormed ewes more than once a year than 

dewormed the other sheep types. The frequency of deworming preweaned and weaned 

lambs may refl ect operation deworming schedule and not apply to individual animals 

(e.g., cannot deworm a preweaned lamb less than once per year because of short 

duration for this life stage). 

F.2.i. Percentage of operations by frequency of deworming sheep using conventional or 

natural/alternative dewormers during 2010, and by sheep type:

Percent Operations 

 Frequency

Never

Less than 

once a year Once a year

More than 

once a year

Sheep type Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Total

Preweaned lambs 58.8 (2.1) 4.7 (1.0) 20.4 (1.8) 16.0 (1.6) 100.0

Weaned 

replacement 

lambs

18.3 (1.6) 2.9 (0.7) 28.0 (1.9) 50.6 (2.2) 100.0

Weaned 

market lambs 35.9 (2.1) 3.8 (0.8) 26.9 (2.0) 33.3 (2.1) 100.0

Ewes 8.6 (1.0) 4.2 (0.9) 22.9 (1.7) 64.2 (2.0) 100.0

A higher percentage of operations in the Central region (18.0 percent) never dewormed 

their sheep compared with operations in the West or East regions (6.6 and 1.7 percent, 

respectively). 

F.2.j. Percentage of operations that never used conventional or natural/alternative 

dewormers on any sheep or lambs during 2010, by region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

6.6 (2.5) 18.0 (2.4) 1.7 (0.7) 8.1 (1.0)
128 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

The dewormers used by the highest percentage of operations were from the classes 

benzimidazole (69.1 percent of operations) and avermectin (69.0 percent). A higher 

percentage of operations in the West region used an avermectin product compared with 

operations in the Central or East regions. A higher percentage of operations in the East 

region used a moxidectin product compared with operations in the Central and West 

regions. 

F.2.k. For operations that used conventional or natural/alternative dewormers during 

2010, percentage of operations by type of natural or chemical dewormers used, and by 

region:

Percent Operations

Region

West Central East

All

operations

Dewormer Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

High tannin concentrate 

plants (e.g., lespedeza) 0.2 (0.2) 0.4 (0.3) 0.9 (0.5) 0.6 (0.3)

Natural or alternative 

dewormers (e.g., 

diatomaceous earth, 

botanicals, herbs, 

cayenne pepper, 

copper oxide wire 

particles)

3.1 (2.2) 8.3 (2.5) 5.9 (1.6) 6.2 (1.2)

Avermectin (e.g., 

Dectomax®, Ivomec®) 87.3 (3.7) 66.2 (3.5) 64.6 (3.2) 69.0 (2.1)

Moxidectin (e.g., 

Cydectin®/Quest®) 18.2 (4.4) 24.1 (3.3) 42.5 (3.1) 32.9 (2.1)

Benzimidazole (e.g., 

Valbazen®) 65.6 (5.4) 59.7 (3.7) 75.6 (2.9) 69.1 (2.1)

Morantel (e.g., 

Rumatel®) or Pyrantel 

(e.g., Strongid®)

1.5 (1.5) 0.3 (0.3) 2.3 (1.1) 1.6 (0.6)

Levamisole 

(e.g., Prohibit®) 25.1 (4.9) 12.4 (2.5) 23.3 (2.6) 20.3 (1.8)

Other 1.5 (1.5) 0.0 (—) 1.0 (0.7) 0.8 (0.4)
USDA APHIS VS / 129 

Section I: Population Estimates–F. Parasites and Deworming

3. Dewormer effi cacy and information sources

The most commonly used method to prolong or improve the effi cacy of dewormers was to 

rotate dewormer type. The majority of operations (70.4 percent) rotated dewormer types 

during 2010. About one-fourth of operations (26.9 percent) chose to deworm more often, 

while 33.0 percent dewormed less often/strategically as a means to prolong or improve 

the effi cacy of the dewormers. There were no substantial differences by region, fl ock size, 

or fl ock type (data not shown). 

F.3.a. For operations that used conventional or natural/alternative dewormers in sheep 

during 2010, percentage of operations by method used to prolong or improve the effi cacy 

of the dewormers used, and by region:

Percent Operations

Region

West Central East

All

operations

Technique Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Rotate dewormer type 66.9 (5.3) 66.4 (3.5) 73.8 (3.0) 70.4 (2.1)

Monitor effectiveness

by fecal testing 11.9 (3.6) 7.1 (1.6) 11.8 (2.0) 10.4 (1.3)

Deworm more often 22.5 (4.6) 22.0 (3.2) 31.2 (3.1) 26.9 (2.1)

Deworm less often/

strategically 34.1 (5.4) 22.9 (3.3) 38.5 (3.2) 33.0 (2.2)

Other 7.2 (3.0) 3.6 (1.4) 8.1 (1.7) 6.6 (1.1)
130 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

The appearance of the sheep was the primary method used by the majority of operations 

(67.2 percent) to determine whether or not a dewormer was working. 

F.3.b. For operations that used conventional or natural/alternative dewormers on sheep 

during 2010, percentage of operations by primary method used to determine whether or 

not the dewormer program was working, and by region:

Percent Operations

Region

West Central East

All

operations

Primary method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Achieve expected 

performance 6.1 (2.7) 13.2 (2.3) 14.2 (2.3) 12.6 (1.5)

Appearance of sheep 67.0 (5.3) 72.2 (3.2) 64.4 (3.1) 67.2 (2.1)

Fecal consistency 

(no diarrhea) 10.6 (3.5) 6.6 (2.1) 4.2 (1.3) 6.0 (1.1)

Improved eye score 0.4 (0.4) 1.5 (0.7) 6.5 (1.5) 4.0 (0.8)

Laboratory testing 3.2 (2.1) 2.4 (0.9) 3.8 (1.2) 3.3 (0.8)

Other 12.6 (3.5) 4.1 (1.1) 7.0 (1.6) 7.0 (1.1)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 131 

Section I: Population Estimates–F. Parasites and Deworming

For the 91.9 percent of operations that used either conventional or natural/alternative 

dewormers (table F.2.j), the primary information sources regarding deworming were 

veterinarian (69.1 percent of operations) and other sheep producers (66.8 percent). 

F.3.c. For operations that used conventional or natural/alternative dewormers on sheep 

during 2010, percentage of operations that ranked the following sources of deworming 

information as somewhat or very important, by region:

Percent Operations

Region

West Central East

All

operations

Information source Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Veterinarian 61.9 (5.4) 69.1 (3.7) 71.4 (3.0) 69.1 (2.1)

Other sheep producers 64.0 (5.4) 62.4 (3.7) 70.3 (3.1) 66.8 (2.2)

Sales representative 14.3 (3.7) 18.5 (2.5) 20.9 (2.6) 19.0 (1.7)

Extension/

university personnel 34.0 (5.2) 39.5 (3.5) 48.3 (3.2) 43.2 (2.2)

Magazines/

journals/club or 4-H 

publications (articles and/

or ads)

47.4 (5.5) 51.4 (3.7) 63.1 (3.2) 56.9 (2.2)

Internet 38.0 (5.5) 32.8 (3.5) 44.7 (3.3) 40.0 (2.3)

Other 5.1 (2.5) 8.6 (2.4) 5.6 (1.5) 6.4 (1.2)
132 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

There was no difference between fl ock sizes in whether a veterinarian was involved 

in the diagnosis of parasite infections. Overall, 33.7 percent of operations involved a 

veterinarian in the diagnosis of parasite infections.

F.3.d. Percentage of operations by level of veterinarian’s involvement regarding diagnosis 

of parasite infections, and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Level of 

involvement Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Very involved 11.2 (1.8) 12.6 (1.9) 14.1 (3.0) 11.7 (1.4)

Somewhat 

involved 21.6 (2.3) 21.5 (2.8) 28.7 (4.9) 22.0 (1.8)

Not involved 67.3 (2.7) 66.0 (3.1) 57.2 (5.1) 66.4 (2.0)

Total 100.0 100.0 100.0 100.0

While 69.1 percent of producers thought the veterinarian was an important source of 

deworming information (table F.3.c), just 44.7 percent indicated veterinarians were very 

or somewhat involved with decisions about treatments. Regardless of size, over half 

of operations that treated their sheep with a dewormer (55.3 percent) did not include 

a veterinarian in the decision about parasite treatments. There were no substantial 

differences by region (data not shown).

F.3.e. Percentage of operations by level of veterinarian’s involvement regarding decisions 

about parasite treatments (dewormer), and by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Level of 

involvement Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Very involved 15.4 (2.1) 16.0 (2.2) 20.9 (4.7) 15.8 (1.6)

Somewhat 

involved 29.2 (2.7) 28.4 (3.4) 26.4 (4.7) 28.9 (2.1)

Not involved 55.4 (3.0) 55.6 (3.5) 52.7 (5.7) 55.3 (2.3)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 133 

Section I: Population Estimates–F. Parasites and Deworming

Overall, just 8.7 percent of operations used a fecal egg count reduction test to determine 

whether resistance to dewormers was occurring on their operations. 

F.3.f. For operations that dewormed, percentage of operations by fecal test used to 

determine resistance to dewormers during 2010:

Fecal test

Percent 

operations

Std. 

error

Fecal egg count reduction (worm egg count 

both before and after deworming) 8.7 (1.2)

DrenchRite 

(assay for resistance to dewormers) 0.6 (0.4)

Other 0.2 (0.2)

4. Fly, ked, and tick control

External parasites (ectoparasites) can be a cause of economic loss on U.S. sheep 

operations and are often controlled through the use of insecticides. These parasites 

include a number of fl y species, some of which can deposit eggs in wounds or larvae 

in nasal passages. Fly larvae feed on tissue until the next stage in their life cycle and 

cause extensive tissue damage. Ectoparasites also include keds, blood-sucking fl ies 

commonly referred to as sheep ticks. Ked bites cause irritation, wool loss due to rubbing 

or biting, and reduced weight gain due to discomfort. The bites may cause hard nodules 

on the skin, which reduce the value of pelts. True ticks are not host specifi c, are widely 

distributed throughout the United States and, while generally not a serious concern for 

sheep, may be responsible for disease transmission. It is likely at least some producers 

answered questions regarding tick control as if the control was for keds.
134 / Sheep 2011

Section I: Population Estimates–F. Parasites and Deworming

Nearly one-third of operations (30.7 percent) used control methods for fl ies and/or 

keds during 2010, and 19.3 percent used control methods for ticks. Over half of large 

operations (59.2 percent) used a control method for fl ies and/or keds compared with just 

one-fourth of small operations (25.4 percent). A higher percentage of large operations 

used pour-on products for fl ies, keds, and ticks compared with small and medium 

operations. 

F.4.a. Percentage of operations that used the following control methods for fl ies and/or 

keds, and ticks during 2010, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Control method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Flies and/or keds

Pour-on product 14.5 (1.8) 27.4 (2.8) 42.1 (4.7) 19.4 (1.5)

Topical spray 14.5 (2.0) 14.6 (2.6) 21.6 (4.2) 15.0 (1.6)

Dip 0.7 (0.5) 0.1 (0.1) 0.0 (—) 0.6 (0.4)

Any 25.4 (2.4) 38.4 (3.3) 59.2 (5.3) 30.7 (1.9)

Ticks

Pour-on product 10.6 (1.6) 18.4 (2.1) 38.2 (4.6) 14.2 (1.3)

Topical spray 4.6 (1.2) 5.5 (1.6) 16.7 (3.9) 5.5 (0.9)

Dip 0.4 (0.4) 1.4 (1.3) 0.0 (—) 0.6 (0.4)

Any 14.5 (1.9) 24.3 (2.8) 53.6 (5.2) 19.3 (1.5)
USDA APHIS VS / 135 

Section I: Population Estimates–F. Parasites and Deworming

Pour-on products were used by a higher percentage of operations in the Central region to 

control fl ies and/or keds and ticks compared with operations in the East region. 

F.4.b. Percentage of operations that used the following control methods for fl ies and/or 

keds, and ticks during 2010, by region:

Percent Operations

Region

West Central East

Control method Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

Flies and/or keds

Pour-on product 19.3 (4.2) 29.5 (2.8) 12.3 (1.8)

Topical spray 18.9 (4.2) 14.0 (2.3) 14.3 (2.3)

Dip 1.6 (1.5) 0.9 (0.8) 0.0 (—)

Any 35.1 (5.1) 39.5 (3.1) 23.0 (2.6)

Ticks

Pour-on product 15.7 (3.9) 23.5 (2.4) 7.2 (1.4)

Topical spray 6.7 (2.4) 8.2 (1.8) 3.4 (1.2)

Dip 0.0 (—) 0.9 (0.8) 0.6 (0.6)

Any 21.7 (4.3) 31.1 (2.8) 10.2 (1.8)
136 / Sheep 2011

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

Alternating sheep grazing with either another domestic species or crop or hay production 

can reduce parasite loads on pastures. 

1. Pasture management

The majority of operations (85.5 percent) alternated pasture methods or commingled 

sheep with other species during 2010. A higher percentage of operations in the Central 

region (36.8 percent) commingled cattle or horses with ewe/lamb pairs compared with 

operations in the East region (23.4 percent). 

G.1.a. Percentage of operations that grazed sheep on pasture during 2010, by pasturing 

method and by region: 

Percent Operations

Region

West Central East

All

operations

Pasturing method Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Alternated grazing sheep 

and other domestic 

species, such as cattle 

or horses

26.7 (4.6) 33.6 (3.1) 25.2 (2.8) 28.4 (1.9)

Commingled cattle or 

horses with ewe/lamb 

pairs

23.1 (4.5) 36.8 (3.2) 23.4 (2.5) 28.0 (1.8)

Alternated grazing 

sheep and crop or hay 

production

36.4 (4.8) 45.7 (3.3) 44.6 (3.2) 43.6 (2.1)

Any of the above 88.7 (3.6) 82.1 (2.7) 86.7 (2.2) 85.5 (1.6)

G.1.b. Percentage of operations that used pasture rotation during 2010, by region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

75.1 (4.6) 61.9 (3.2) 73.5 (2.9) 69.8 (2.0)

G. Pasture 

Management, 

Water Sources, 

and Feeding 

Practices
USDA APHIS VS / 137 

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

Over half of operations that used pasture rotation (55.2 percent) rested pastures for 22 to 

63 days between grazing sheep. A higher percentage of operations in the Central region 

than in the other regions allowed pastures to rest for more than 9 weeks between grazing 

sheep.

G.1.c. For operations that used pasture rotation, percentage of operations by number of 

days pasture was allowed to rest between grazing sheep, and by region:

Percent Operations

Region

West Central East

All

operations

Number of days Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

1–21 34.5 (5.8) 18.0 (3.1) 44.9 (3.8) 34.8 (2.5)

22–63 58.6 (6.0) 57.3 (4.2) 52.8 (3.8) 55.2 (2.6)

64 or more 7.0 (2.6) 24.8 (3.7) 2.3 (1.1) 10.0 (1.4)

Total 100.0 100.0 100.0 100.0

Just over half of all operations (51.4 percent) placed harvested or commercial feed 

directly on the ground for sheep to eat, ranging from 46.1 percent of small operations to 

75.5 percent of large operations. 

G.1.d. Percentage of operations that placed harvested or commercial feed directly on the 

ground for sheep to eat during 2010, by fl ock size:

Percent Operations

Flock Size (number of ewes)

Small

(20–99) 

Medium

(100–499)

Large

(500 or more)

All 

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

46.1 (2.8) 60.2 (3.5) 75.5 (4.9) 51.4 (2.2)
138 / Sheep 2011

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

A higher percentage of operations in the Central region (65.4 percent) placed harvested 

or commercial feed directly on the ground for sheep to eat compared with operations in 

the West or East regions. 

G.1.e. Percentage of operations that placed harvested or commercial feed directly on the 

ground for sheep to eat during 2010, by region:

Percent Operations

Region

West Central East

Percent Std. error Percent Std. error Percent Std. error

45.5 (5.4) 65.4 (3.1) 43.5 (3.3)

Photograph courtesy of American Sheep Industry Association.
USDA APHIS VS / 139 

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

2. Water sources

Approximately three-fourths of operations provided sheep access to a bucket, trough, 

or waterer in which the rim was less than 2 feet off the ground (higher likelihood of fecal 

contamination), regardless of season (winter or summer) or region. A higher percentage 

of operations in the West region had a stream (or other running water) during winter 

compared with operations in the other regions.

G.2.a. Percentage of operations in which the fl ock typically had access to the following 

water sources during winter and summer, by region: 

Percent Operations

Region

West Central East

All

operations

Water source Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Winter

Pond/lake/reservoir 

(or other standing 

water)

33.6 (5.0) 28.3 (3.3) 16.7 (2.4) 23.4 (1.8)

Stream (or other 

running water) 47.9 (5.4) 22.3 (2.8) 26.6 (2.8) 28.7 (1.9)

Bucket, trough, or 

waterer in which 

rim was less than 

2 ft off the ground

79.1 (4.4) 76.4 (2.9) 74.8 (2.7) 76.1 (1.8)

Bucket, trough, or 

waterer in which 

rim was 2 ft or more 

off the ground

39.3 (5.3) 36.3 (3.2) 38.7 (3.1) 38.0 (2.1)

Other 0.7 (0.6) 7.9 (1.6) 2.8 (0.9) 4.2 (0.7)

Summer

Pond/lake/reservoir 

(or other standing 

water)

30.4 (4.6) 46.2 (3.3) 35.2 (3.0) 38.1 (2.0)

Stream (or other 

running water) 42.5 (5.2) 43.9 (3.2) 38.1 (3.1) 40.8 (2.1)

Bucket, trough, or 

waterer in which rim 

was less than 

2 ft off the ground

77.6 (4.6) 68.0 (3.1) 74.2 (2.8) 72.6 (1.9)

Bucket, trough, or 

waterer in which 

rim was 2 ft or more 

off the ground

33.7 (5.1) 32.5 (3.2) 37.4 (3.1) 35.1 (2.1)

Other 0.7 (0.6) 2.2 (1.3) 0.7 (0.5) 1.2 (0.5)
140 / Sheep 2011

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

The primary source of water for operations during winter and summer was a bucket, 

trough, or waterer in which the rim was less than 2 feet off the ground. The next most 

common water source in winter and summer was a bucket, trough, or waterer in which 

the rim was 2 feet or more off the ground. 

G.2.b. Percentage of operations by primary water source during winter and summer, by 

region:

Percent Operations

Region

West Central East

All

operations

Primary 

water source Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error Pct.

Std. 

error

Winter

Pond/lake/reservoir 

(or other standing 

water)

3.6 (1.6) 4.8 (1.8) 1.7 (0.8) 3.1 (0.8)

Stream (or other 

running water) 15.2 (3.8) 7.9 (1.7) 7.3 (1.7) 8.8 (1.2)

Bucket, trough, or 

waterer in which rim 

was less than 

2 ft off the ground

52.6 (5.4) 53.9 (3.4) 58.2 (3.1) 55.8 (2.1)

Bucket, trough, or 

waterer in which rim 

was 2 ft or more off 

the ground

19.0 (4.3) 20.5 (2.8) 25.3 (2.7) 22.6 (1.8)

Other water source 2.0 (1.5) 6.6 (1.1) 2.8 (1.0) 4.0 (0.7)

Multiple water sources 

used equally 7.7 (2.6) 6.3 (1.6) 4.8 (1.4) 5.8 (1.0)

Total 100.0 100.0 100.0 100.0

Summer

Pond/lake/reservoir 

(or other standing 

water)

3.0 (1.6) 16.1 (2.5) 5.9 (1.4) 8.9 (1.1)

Stream (or other 

running water) 14.3 (3.8) 18.0 (2.0) 10.8 (2.0) 13.9 (1.4)

Bucket, trough, or 

waterer in which rim 

was less than 

2 ft off the ground

55.2 (5.4) 40.0 (3.3) 52.3 (3.1) 48.5 (2.1)

Bucket, trough, or 

waterer in which rim 

was 2 ft or more off 

the ground

19.1 (4.3) 16.9 (2.7) 21.2 (2.6) 19.4 (1.7)

Other water source 2.0 (1.5) 2.2 (0.8) 0.7 (0.6) 1.4 (0.5)

Multiple water sources 

used equally 6.5 (2.3) 7.0 (1.6) 9.1 (1.8) 7.9 (1.1)

Total 100.0 100.0 100.0 100.0
USDA APHIS VS / 141 

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

3. Feeding practices

On just under two-thirds of operations (61.9 percent), weaned lambs less than 12 months 

of age shared common feed or water sources with adult sheep.

G.3.a. Percentage of operations in which weaned lambs less than 12 months of age 

generally shared common feed or water sources with adult sheep, by region: 

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

66.7 (5.2) 68.7 (3.0) 55.6 (3.1) 61.9 (2.0)

G.3.b. Percentage of operations in which weaned lambs less than 12 months of age 

generally shared common feed or water sources with adult sheep, by region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

23.7 (4.7) 24.4 (2.7) 28.3 (2.9) 26.2 (1.9)
142 / Sheep 2011

Section I: Population Estimates–G. Pasture Management, Water Sources, and Feeding Practices

Placing thin ewes with younger sheep can expose the younger sheep to chronic diseases 

such as Johne’s disease. Approximately one-fourth of operations (26.2 percent) placed 

young sheep with thin ewes to encourage or increase the ewes’ feed intake. 

G.3.c. Percentage of operations that ever placed thin ewes with younger sheep to 

encourage or to increase the ewes’ feed intake, by region:

Percent Operations

Region

West Central East

All

operations

Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error Pct.

Std.

error

23.7 (4.7) 24.4 (2.7) 28.4 (2.9) 26.2 (1.9)
USDA APHIS VS / 143 

Section II: Methodology

NAHMS develops study objectives by exploring existing literature and contacting industry 

members about their informational needs and priorities during a needs assessment 

phase. The needs assessment for the NAHMS Sheep 2011 study collected information 

from U.S. sheep producers and other sheep specialists about what they perceived to 

be the most important sheep health and productivity issues. A driving force of the needs 

assessment was the desire of NAHMS to receive as much input as possible from a 

variety of producers, industry experts and representatives, veterinarians, extension 

specialists, universities, Federal and State governments, and industry organizations. 

Information was collected through a needs assessment questionnaire, and top issues 

were prioritized by teleconferences with representatives of the sheep industry, along with 

extension agents and other university affi liates. 

The needs assessment for Sheep 2011 was conducted from December 2009 

through February 2010. A total of 275 stakeholders completed the needs assessment 

questionnaire. In addition, a focus group of producers, researchers, extension 

veterinarians, and clinicians helped develop the study objectives. Of these, 37 percent 

were meat producers, 14 percent wool producers, 0.8 percent milk producers, 

8.0 percent 4-H or club lamb participants, 1.9 percent veterinarians, 21.8 percent 

Federal or State governments, 5.3 percent university or extension agents, 0.8 percent 

allied industry, and 10.3 percent classifi ed themselves as “other,” which included mostly 

producers of meat and wool, hair sheep, or seed stock. The number of sheep raised 

by producers was between 1 and 5,000. Of the respondents, 49.2 percent were from 

the Eastern time zone, 34.9 percent from the Central time zone, 7.0 percent from the 

Mountain time zone, and 8.9 percent from the Pacifi c time zone. 

Ewe health/management was the most important management issue, with 40 percent 

of respondents ranking health/management as either their fi rst, second, or third most 

important issue. For producers who indicated ewe health as a priority, their specifi c areas 

of interest included: mastitis, Q fever, ovine progressive pneumonia, Johne’s disease, 

abortion prevention, parasites, nutrition, and proactive information for ewe health. 

Internal parasites were the most important disease issue for survey respondents. Overall, 

65.7 percent of respondents ranked internal parasites as one of their top three disease 

issues. This top ranking held true for producer respondents and veterinary and university 

extension agents. The next most important disease issues were scrapie (22.0 percent of 

respondents), abortions (19.8 percent), and lameness (19.8 percent). 

Federal and State veterinarians made up nearly 22 percent of respondents. The following 

describes their responses to the survey: The top three management issues were: 

identifi cation (15.9 percent), infectious disease (15.2 percent), and disease prevalence 

(13.4 percent). The top three disease-specifi c issues were: scrapie (18.1 percent), 

internal parasites (13.6 percent), and Johne’s disease (10.6 percent).

Section II: Methodology

A. Needs 

Assessment
144 / Sheep 2011

Section II: Methodology

Once the most important issues were identifi ed, the study objectives were created 

by prioritizing the needs during discussions with producers, veterinarians, university 

extension agents, and government personnel. 

Objectives for NAHMS Sheep 2011 study were:

 Describe trends in sheep health and management practices from 1996 to 

2011.

 Describe management and biosecurity practices used to control common 

infectious diseases, including scrapie, ovine progressive pneumonia, Johne’s 

disease, and caseous lymphadenitis. 

 Estimate the prevalence of gastrointestinal parasites and anthelmintic 

resistance.

 Estimate the prevalence of Mycoplasma ovipneumonie in domestic sheep 

fl ocks. Relate presence of the organism in blood and nasal secretions to 

clinical signs and demographic and management factors. 

 Facilitate the collection of information and samples regarding causes of 

abortion storms in sheep.

 Determine producer awareness of the zoonotic potential of contagious 

ecthyma (sore mouth) and the management practices used to prevent 

transmission of the disease.

 Provide sera to include in the serological bank for future research. 

1. State selection

The preliminary selection of States to be included in the study was done from January 

through April 2010, using the National Agricultural Statistics Service (NASS) 2007 Census 

of Agriculture and the January 29, 2010, “Sheep and Goat Report.” A goal for NAHMS 

national studies is to include States that account for at least 70 percent of animals and 

producer populations in the United States. The 22 States recommended for inclusion 

in the study were California, Colorado, Iowa, Idaho, Kentucky, Kansas, Michigan, 

Minnesota, Missouri, Montana, New Mexico, New York, Ohio, Oregon, Pennsylvania, 

South Dakota, Texas, Utah, Virginia, Washington, Wisconsin, and Wyoming. These 

States, according to the 2007 Census of Agriculture, represented 85.5 percent of the U.S. 

ewe inventory and 70.1 percent of farms with ewes. In addition, the States included 

84.6 percent of the January 1, 2010, ewe inventory (NASS annual ewe inventory, 2010).

A memo identifying these 22 States was provided in July 2010 to the USDA–APHIS–

VS–CEAH Director and, in turn, the VS regional directors. Each regional director sought 

input from the respective States about being included or excluded from the study. The 22 

States were included in the study. 

B. Sampling and 

Estimation
USDA APHIS VS / 145 

Section II: Methodology

2. Operation selection

The list sampling frame was provided by NASS. Within each State a stratifi ed random 

sample was selected. The size stratum was the number of sheep and lambs for each 

operation on the list sampling frame at the time of sample selection. These procedures 

were used to select the sample for the NASS January 2010 Sheep survey. Sampling 

effi ciencies were gained by drawing a subsample of respondents to this survey. This 

procedure eliminated a large number of out-of-business and zero-inventory reports. The 

sample was selected from those producers who reported one or more ewes on hand 

January 1, 2010. The sample of sheep producers was selected in each State. Among 

producers reporting fewer than 20 ewes, 1,381 operations were selected for Phase Ia. 

For operations reporting 20 or more ewes, a total of 3,539 operations were selected 

for contact during Phase Ib. Therefore a total of 4,920 operations were selected for the 

study.

Operations with 20 or more ewes that participated in Phase I were invited to participate in 

data collection for Phase II. A total of 1,240 operations agreed via written consent to be 

contacted by veterinary medical offi cers as part of Phase II in the study. 

3. Population inferences

a. Phases Ia and Ib: general sheep management questionnaire

Inferences cover the population of sheep producers with at least 1 ewe on hand January 

1, 2010, in the 22 participating States. As of December 31, 2007 (2007 Census of 

Agriculture), these States accounted for 85.5 percent of all ewes in the United States 

(3,005,813 head out of 3,516,409) and 70.1 percent of farms with ewes (47,855 out of 

68,222). In addition, these States accounted for 84.6 percent of the January 1, 2010, ewe 

inventory in the United States or 2,824,000 head out of 3,340,000 head. (See appendix 

II for respective data on individual States.) All respondent data were statistically weighted 

to refl ect the population from which they were selected. The inverse of the probability 

of selection by strata for each operation was the initial selection weight. This selection 

weight was adjusted for nonresponse within each State and size group from the NASS 

survey as well as adjusted for subsampling and again for nonresponse to this study. 

These adjustments and weighting allow for inferences back to the original population 

from which the sample was selected.

b. Phase II: VS visit

Inferences cover the population of sheep producers with 20 or more ewes in the 22 

participating States. For operations eligible for Phase II data collection (those with 20 or 

more ewes that completed the general sheep management questionnaire) weights were 

adjusted to account for operations that did not want to continue to Phase II. The 22-State 
146 / Sheep 2011

Section II: Methodology

target population of operations with 20 or more ewes was estimated to represent 

74.5 percent of all sheep operations with 20 or more ewes in the 22 States on January 1, 

2011 (see appendix II).

1. Data collectors and data collection period

a. Phases Ia and 1b: general sheep management questionnaire

All data were collected from January 1 to February 11, 2011. Producers with fewer than 

20 ewes were contacted via telephone interviewers who administered the questionnaire, 

which averaged approximately 30 minutes. NASS enumerators administered the general 

sheep management questionnaire to producers with 20 or more ewes via an in-person 

interview, which took approximately 1 hour. 

b. Phase II: VS visit

Data were collected from producers by Federal or State veterinary medical offi cers 

(VMOs) or animal health technicians (AHTs) from March 14 to June 30, 2011. The 

interview took approximately 1.5 hours. 

1. Phase I: Validation—general sheep management questionnaire

Telephone interviews were conducted via computer-assisted telephone interview 

software at each individual State NASS offi ce and edited. For the in-person administered 

questionnaire, initial data entry and validation for the general sheep management 

questionnaire were also performed in the individual NASS State offi ces. Data were 

entered into a SAS data set and edited. Individual State data fi les were then combined 

and sent to NAHMS national staff, which performed additional data validation on the 

entire data set. 

2. Phase II: Validation—VS visit questionnaires

After completing the VS visit questionnaires, data collectors sent them to their respective 

State NAHMS coordinators who reviewed the questionnaire responses for accuracy. Data 

entry and validation were completed by CEAH staff using SAS.

C. Data 

Collection

D. Data Analysis
USDA APHIS VS / 147 

Section II: Methodology

The purpose of this section is to provide various performance measurement parameters. 

Historically, the term “response rate” was used as a catchall parameter, but there 

are many ways to defi ne and calculate response rates. Therefore, the following table 

presents an evaluation based on a number of response measurement parameters, which 

are defi ned with an “x” in categories that contribute to the measurement.

1. Phase Ia: general sheep management questionnaire—fewer than 20 ewes 

A total of 1,381 operations were selected for the survey. Of these operations, 

64.2 percent completed the questionnaire. 

Measurement parameter

Response category

Number 

operations

Percent 

operations Contacts Usable1 Complete2

Refused GSM 

questionnaire/inaccessible 298 21.6 x4

Ineligible (no sheep or 

lambs on Jan. 1, 2011) 196 14.2 x x

Complete 887 64.2 x x x

Total 1,381 100.0 887 887

Percent of total 

operations 64.2 64.2

Percent of total 

operations weighted3 60.6 60.6

1

Useable operation—respondent provided answers to inventory questions for the operation (either zero or 

positive number on hand).

2

Survey complete operation—respondent provided answers to all or nearly all questions.

3

Weighted response—the rate was calculated using the initial selection weights.

4

The number of operations that refused verses those that were not contacted was not tracked.

E. Sample 

Evaluation
148 / Sheep 2011

Section II: Methodology

2. Phase Ib: general sheep management questionnaire—20 or more ewes 

A total of 3,539 operations were selected for the questionnaire. Of these operations, 

3,191 (90.2 percent) were contacted. There were 2,661 operations that provided 

usable inventory information (75.2 percent of the total selected and 83.4 percent of 

those contacted). In addition, there were 2,369 operations (66.9 percent) that provided 

“complete” information for the questionnaire. 

Measurement parameter

Response category

Number 

operations

Percent 

operations Contacts Usable1 Complete2

Zero sheep on 

January 1, 2011 211 5.9 x x

Out of business 81 2.3 x x

Refused GSMQ 

questionnaire 530 15.0 x

Complete VMO 

consent signed 1,241 35.1 x x x

Complete VMO 

consent refused 1,025 29.0 x x x

Complete,

ineligible for VMO

103 2.9 x x x

Out of scope 17 0.5

Offi ce hold (NASS 

elected not to contact) 69 1.9

Inaccessible 262 7.4

Total 3,539 100.0 3,191 2,661 2,369

Percent of total 

operations 90.2 75.2 66.9

Percent of total 

operations weighted3 90.9 77.9 68.5

1

Useable operation—respondent provided answers to inventory questions for the operation (either zero or 

positive number on hand).

2

Survey complete operation—respondent provided answers to all or nearly all questions.

3

Weighted response—the rate was calculated using the initial selection weights.
USDA APHIS VS / 149 

Section II: Methodology

3. Phase II: VS initial visit questionnaire

There were 1,241 operations that consented during Phase I to be contacted by a 

veterinary medical offi cer (VMO) for Phase II. Of these 1,241, 761 (61.3 percent) agreed 

to continue in Phase II of the study and completed the VMO initial visit questionnaire; 330 

(26.6 percent) refused to participate. Approximately 11.0 percent of the 1,291 operations 

were not contacted, and 1.0 percent were ineligible because they had fewer than 20 

sheep at the time they were contacted by the VMO during Phase II of the study.

Measurement parameter

Response category

Number 

operations

Percent 

operations Contacts Usable1 Complete2

Survey complete 761 61.3 x x x

Survey refused 330 26.6 x

Not contacted 137 11.0

Ineligible3 13 1.0 x x

Total 1,241 100

Percent of total 

operations 89.0 62.4 61.4

Percent of total 

operations weighted4 88.1 59.6 58.4

1

Useable operation—respondent provided answers to inventory questions for the operation (either zero or 

positive number on hand).

2

Survey complete operation—respondent provided answers to all or nearly all questions.

3

Ineligible—no ewes at time of interview, which occurred from March 14 to June 30, 2011.

4

Weighted response—the rate was calculated using the initial selection weights.
150 / Sheep 2011

Appendix I: Sample Profi le

1. Number of responding operations, by herd size

Phase Ia: 

general sheep 

management 

questionnaire—

fewer than 20 ewes

Phase Ib: general 

sheep management 

questionnaire—20 

or more ewes

Phase II: VS 

initial visit 

questionnaire

Herds 

(number of ewes) Number of responding operations

Fewer than 20 887

20 to 99 1,049 343

100 to 499 859 287

 500 or more 461 131

Total 887 2,369 761

2. Number of responding operations, by region

Phase Ia: 

general sheep 

management 

questionnaire—

fewer than 20 ewes

Phase Ib: general 

sheep management 

questionnaire—20 

or more ewes

Phase II: VS 

initial visit 

questionnaire

Region Number of responding operations

West 175 325 116

Central 348 1,208 349

East 364 836 296

Total 887 2,369 761

A. Responding 

Operations

Appendix I: Sample Profi le
USDA APHIS VS / 151 

Appendix II: U.S. Ewe Population and Farms

Number of Ewes Number of Farms

Region State

Ewes on 

farms with 

1 or more 

head

Ewes on 

farms with 

20 or more 

head

Pct. of 

total

Farms with 

1 or more 

head

Farms with 

20 or more 

head

Pct. of 

total

West CA 286,544 269,021 93.9 3,413 946 27.7

OR 119,356 104,842 87.8 2,802 804 28.7

WA 35,138 (D) 1,977 367 18.6

 Total 441,038 (D) 8,192 2,117 25.8

Central CO 200,269 194,698 97.2 1,265 493 39.0

ID 161,935 (D) 1,047 367 35.1

KS 52,614 48,143 91.5 1,011 450 44.5

MT 184,087 (D) 1,375 859 62.5

NM 87,131 78,150 89.7 2,152 756 35.1

SD 210,005 (D) 1,580 1,231 77.9

TX 580,861 550,346 94.7 6,814 2,694 39.5

UT 210,388 203,621 96.8 1,430 514 35.9

WY 258,096 255,618 99.0 817 495 60.6

 Total 1,945,386 (D) 17,491 7,859 44.9

East IA 128,518 113,364 88.2 3,168 1,606 50.7

KY 22,225 15,880 71.5 1,171 309 26.4

MI 48,398 38,932 80.4 1,969 582 29.6

MN 85,049 75,343 88.6 2,225 1,038 46.7

MO 51,328 41,933 81.7 1,911 718 37.6

NY 42,321 35,260 83.3 1,523 497 32.6

OH 74,331 59,700 80.3 2,929 1,103 37.7

PA 62,828 46,728 74.4 3,067 837 27.3

VA 48,219 38,991 80.9 1,796 691 38.5

WI 56,172 44,057 78.4 2,413 780 32.3

 Total 619,389 510,188 82.4 22,172 8,161 36.8

Total (22 States) 3,005,813 (D) 47,855 18,137 37.9

Percent of U.S. 85.5 70.1 74.5

Total U.S. (50 States) 3,516,409 3,193,721 90.8 68,222 24,346 35.7

Source: NASS 2007 Census of Agriculture.

Appendix II: U.S. Ewes Population and Farms

A. Number of Ewes–State, Region, and United States
152 / Sheep 2011

Appendix II: U.S. Ewe Population and Farms

B. Ewes, Flock Size Distribution–State, Region, and United States

Flock Size

1–19 20–99 100–499 500 or more

Region State Farms Head Farms Head Farms Head Farms Head

West CA 2,467 17,523 737 28,185 129 24,906 80 215,930

OR 1,998 14,514 633 24,712 133 27,549 38 52,581

WA 1,610 (D) 347 (D) 15 (D) 5 (D)

 Total 6,075 (D) 1,717 (D) 277 (D) 123 (D)

Central CO 772 5,571 347 14,083 88 18,594 58 162,021

ID 680 5,029 276 10,663 50 9,498 41 136,745

KS 561 4,471 353 14,825 76 (D) 21 (D)

MT 516 (D) 486 (D) 277 59,288 96 (D)

NM 1,396 8,981 674 23,660 52 (D) 30 (D)

SD 349 (D) 724 (D) 410 81,396 97 (D)

TX 4,120 30,515 1,762 73,910 666 13,7602 266 338,834

UT 916 6,767 344 14,137 85 15,843 85 173,641

WY 322 2,478 298 13,032 96 21,418 101 221,168

 Total 9,632 (D) 5,264 (D) 1,800 368,680 795 1,284,513

East IA 1,562 15,154 1,357 55,777 236 40,053 13 17,534

KY 862 6,345 277 9,786 30 (D) 2 (D)

MI 1,387 9,466 504 20,852 71 12,595 7 5,485

MN 1,187 9,706 848 33,723 177 32,280 13 9,340

MO 1,193 9,395 626 23,980 87 14,503 5 3,450

NY 1,026 7,061 418 16,213 74 15,064 5 3,983

OH 1,826 14,631 995 38,956 103 17,205 5 3,539

PA 2,230 16,100 740 28,103 90 13,962 7 4,663

VA 1,105 9,228 607 23,140 82 (D) 2 (D)

WI 1,633 12,115 682 26,719 97 (D) 1 (D)

 Total 14,011 109,201 7,054 277,249 1,047 (D) 60 (D)

Total (22 States) 29,718 (D) 14,035 (D) 3,124 604,820 978 1,613,763

Percent of U.S. 67.7 71.7 83.2 84.7 95.0 94.2

Total U.S. (50 States) 43,876 322,688 19,563 767,044 3,753 714,448 1,030 1,712,229

Source: NASS 2007 Census of Agriculture.
USDA APHIS VS / 153 

Appendix II: U.S. Ewe Population and Farms

C. U.S. Sheep and Lamb Population, January 1, 2011, Inventory

Region State

Ewes

(x1,000 head)

Rams

(x1,000 head)

Replacement 

lambs

(x1,000 head)

Total breeding 

sheep and 

lambs

(x1,000 head)

All sheep and 

lambs

(x1,000 head)

West CA 283 12 45 340 610

OR 118 7 23 148 215

WA 36 3 7 46 56

 Total 437 22 75 534 881

Central CO 142 5 28 175 370

ID 153 6 26 185 235

KS 33 2 8 43 70

MT 170 7 38 215 230

NM 77 5 15 97 110

SD 176 7 32 215 275

TX 525 40 125 690 880

UT 211 9 35 255 280

WY 220 8 47 275 365

 Total 1,707 89 354 2,150 2,815

East IA 106 5 19 130 200

KY 22 1.5 4.5 28 34

MI 44 3 11 58 74

MN 77 4 14 95 130

MO 57 3 13 73 81

NY 43 3 10 56 70

OH 81 6 16 103 129

PA 62 6 16 84 98

VA 55 3 9 67 90

WI 59 3 14 76 90

 Total 606 37.5 126.5 770 996

Total (22 States) 2,750 148.5 555.5 3,454 4,692

Percent of U.S. 84.5 78.2 82.9 83.9 84.8

Total U.S. (50 States) 3,255 190 670 4,115 5,530

Source: NASS “Sheep and Goats report,” January 28, 2011.
154 / Sheep 2011

Appendix II: U.S. Ewe Population and Farms

D. Breeding Sheep: Survey Percent by Size Group, United States, 2008–09

1–99 head 200–499 head 500–4,999 head 5,000+ head

2008 2009 2008 2009 2008 2009 2008 2009

Operations 92.5 93.7 6.2 5.2 1.2 1.0 0.1 0.1

Inventory 32.6 36.2 22.7 20.8 30.2 31.3 14.5 11.7

Source: NASS Farms, Land in Farms, and Livestock Operations, 2009 Summary, February 2010.
USDA APHIS VS / 155 

Appendix III: Antibiotic Classes and Product Names

Antibiotic class Active ingredient

Aminoglycoside Gentamicin

Gentamicin sulfate

Neomycin sulfate

Neomycin 

Penicillin Penicillin

Ampicillin trihydrate

Penicillin G benthazine and Pen G Procaine

Penicillin G benzathine

Peniciilin G procaine

Penicillin-dihydrostreptomycin

Cephalosporin Ceftiofur sodium

Ceftiofur crystalline

Ceftiofur hydrochloride

Cephapirin benzathine/cephapirin sodium

Phenicol Florfenicol

Lincosamide Pirlimycin hydrochloride

Macrolide Tulathromycin

Tilmicosin phosphate

Sulfonamide Trimethorim sulfadiazine

Sulfachlorpyridazine

Sulfamethazine

Trimethoprim sulfadiazine

Tetracycline Oxytetracycline

Oxytetracycline hydrochloride

*Not a complete list of available antibiotics in each class.

Appendix III: Antibiotic Classes and Active Ingredients*
156 / Sheep 2011

Appendix IV: Study Objectives and Related Outputs

To develop the objectives for the NAHMS Sheep 2011 study, a needs assessment 

was conducted from December 2009 through February 2010 to determine the current 

issues facing the U.S. sheep industry. A total of 278 stakeholders completed the needs 

assessment questionnaire. In addition, an advisory group of producers, researchers, 

extension veterinarians, and clinicians helped develop the study objectives. 

Objectives for NAHMS Sheep 2011 study 

1. Describe trends in sheep health and management practices from 1996 to 2011.

 Part I: Reference of Sheep Management Practices in the United States, 2011, 

May 2012

 Part II: Reference of Sheep Marketing and Biosecurity Practices in the United 

States, 2011, December 2012

 Part III: Health and Management on U.S. Sheep Operations, 2011, Summer 2013 

 Part IV: Trends in the U.S. Sheep Industry, 1996–2011, expected Fall 2013

 Vaccination Practices on U.S. Sheep Operations, 2011, info sheet, expected 

spring 2013

 Sheep and Lamb Losses on U.S. Sheep Operations, 2011, info sheet, expected 

spring 2013

 Lambing Management on U.S. Sheep Operations, 2011, info sheet, expected 

spring 2013

2. Describe management and biosecurity practices used to control common infectious 

diseases, including scrapie, ovine progressive pneumonia, Johne’s disease, and caseous 

lymphadenitis. 

 Biosecurity Practices on U.S. Sheep Operations, 2011, info sheet, expected 

summer 2013

 Parasite Control on U.S. Sheep Operations, 2011, info sheet, expected summer 

2013

 Producer Disease Awareness, 2011, info sheet, expected summer 2013

 Antimicrobial Drug Use on U.S. Sheep Operations, 2011, info sheet, expected 

summer 2013

3. Estimate the prevalence of gastrointestinal parasites and anthelmintic resistance.

 Gastrointestinal Parasites and Anthelmintic Resistance, 2011, info sheet, 

expected fall 2013

Appendix IV: Study Objectives and Related Outputs
USDA APHIS VS / 157 

Appendix IV: Study Objectives and Related Outputs

4. Estimate the prevalence of Mycoplasma ovipneumonia in domestic sheep fl ocks. 

Relate presence of the organism in blood and nasal secretions to clinical signs and 

demographic and management factors. 

 Mycoplasma ovipneumonia in Domestic Sheep Flocks, 2011, info sheet, 

expected fall 2013

5. Facilitate the collection of information and samples regarding causes of abortion 

storms in sheep.

 Toxoplasmosis in Lambs in U.S. Sheep Flocks, 2011, info sheet, expected fall 

2013

 Q Fever in Sheep in the United States, 2011, info sheet, expected fall 2013

 Campylobacter on U.S. Sheep Operations, 2011, info sheet, expected summer 

2013

 Salmonella on U.S. Sheep Operations, 2011, info sheet, June 2013

6. Determine producer awareness of the zoonotic potential of contagious ecthyma (sore 

mouth) and the management practices used to prevent transmission of the disease.

 Sore Mouth on U.S. Sheep Operations, 2011, info sheet, expected fall 2013
158 / Sheep 2011

Appendix IV: Study Objectives and Related Outputs
USDA APHIS VS / 159 

Appendix IV: Study Objectives and Related Outputs
160 / Sheep 2011

Appendix IV: Study Objectives and Related Outputs
USDA APHIS VS / 161 

Appendix IV: Study Objectives and Related Outputs
Sheep 2011

Table of Contents

Introduction 1

Terms Used in This Report 3

Section I: Population Estimates 3

 A. General Management 5

 1. Ewe age 5

 2. Flock additions 6

 3. Operations with no fl ock additions in 2010 8

 4. Contact with other animals 10

 5. Rodent control 12

 6. Visitors 13

 7. Housing 18

 8. Manure handling 21

 9. Offi cial fl ock identifi cation and ear tags 23

 10. Identifi cation other than offi cial scrapie ear tags 

26

 B. Reproduction Management 28

 1. Calculation of lambing rate 28

 2. Producer-expected (normal or average) lambing 

percentage 31

 3. Lambing season 34

 4. Breeding management for the last completed 

lambing season 35

 5. Lambing outcome 37

 6. Low lambing rate 40

 7. Lamb supplements 47

 8. Ewe synchronization 52

C. Lambing Management 55

 1. Manure and waste beddding management 

during lambing 55

 2. Placenta removal and disposal 58

 3. Abortion 61

 4. Tail docking 67

D. Disease Control and Illness 69

 1. Health management 69

 2. Johne’s disease 76

 3. Scrapie 78

 4. Ovine progressive pneumonia 80

 5. Toxoplasmosis and coxiellosis 83

 6. Diseases present in the last 3 years 84

 7. Vaccination practices 85

 8. Market lamb injections 92

E. Antibiotics 97

 1. Antibiotic use 97

 2. Antibiotic treatment records 99

 3. Antibiotics given 101

 4. Treatment of nursing lambs 104

 5. Treatment of weaned replacement lambs 107

 6. Treatment of weaned market lambs 110

 7. Treatment of ewes 113

 8. Coccidiostats and growth promotants 117

F. Parasites and Deworming 121

 1. Parasites 121

 2. Deworming 122

 3. Deworming effi cacy 129

 4. Fly, ked, and tick control 133

G. Pasture Management 136

 1. Pasture management 136

 2. Water sources 139

 3. Feeding practices 141

Section II: Methodology 143

Appendix I: Sample Profi le 150

Appendix II: U.S. Ewe Population and Farms 151

Appendix III: Antibiotic Classes 155

Appendix IV: Study Objectives and Related Outputs 

156