Veterinary Services 

Centers for Epidemiology and Animal Health February 2009 

_________________________________________________________________________________________________________________________ 

Bull Management Practices 

on U.S. Beef Cow-calf 

Operations 

The U.S. Department of Agriculture’s National 

Animal Health Monitoring System (NAHMS) 

conducted the Beef 2007-08 study, which focused 

on beef cow-calf health and management practices 

in 24 States*. These major beef cow-calf producing 

States represented 79.6 percent of U.S. operations 

with beef cows and 87.8 percent of U.S. beef cows. 

One of the goals of the Beef 2007-08 study was 

to take an in-depth look at bull management 

procedures on U.S. beef cow-calf operations, since 

proper selection and management of bulls is a 

fundamental component of any operation’s 

reproductive program. 

During the Beef 2007-08 study, beef producers 

were asked about their use of artificial insemination 

or natural service, and the methods used to ensure 

that bulls were fertile. 

Bull Breeding 

 The most common breeding method used by 

cow-calf producers is “natural service” by a bull 

only, as opposed to artificial insemination alone or 

in combination with natural service. At least some 

replacement heifers and cows were bred only by 

bulls on nearly all operations (95.7 percent). Most 

heifers and cows were only exposed to a bull (79.2 

percent and 94.2 percent, respectively) (figure 1). 

Ensuring optimal cow-to-bull ratios minimizes 

costs and enhances reproduction. Using too many 

bulls for the same group of females increases the 

risk of injury to the bulls and may result in additional 

expenditures for purchasing and maintaining bulls. 

Overall, cow-calf producers expected mature bulls 

to service 25 females and yearling bulls to service 

17 females. Most reproductive specialists advocate 

*States: 

Alabama, Arkansas, California, Colorado, Florida, Georgia, Idaho, 

Iowa, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, 

Nebraska, New Mexico, North Dakota, Oklahoma, Oregon, South 

Dakota Tennessee, Texas, Virginia, and Wyoming. 

that a mature bull can service 25 to 35 cows; 

however it has been shown that highly fertile bulls 

can service up to 50 cows. 

 

0

20

40

60

80

100

Cows*

Heifers

Breeding Method 

Percent

Figure 1. Percentage of Heifers and Cows Bred or Intended to be 

Bred for Calving in 2007, by Breeding Method

Both artificially

inseminated and

exposed to bulls

79.2

94.2

3.9 1.1

12.4

4.1 4.5 0.6

Only artificially

inseminated Only exposed to bulls Brought on bred females

*Some heifers may have been included in this category.

Reproductive examinations 

An annual reproductive examination is 

important to ensure that bulls are healthy and 

fertile. The percentage of operations that tested the 

semen of at least some bulls in preparation for the 

last breeding season ranged from 18.1 percent of 

operations with 1 to 49 beef cows to 61.1 percent of 

operations with 200 or more beef cows. Similarly, 

scrotal measurements were performed on a lower 

percentage of operations with 1 to 49 cows than on 

larger operations (figure 2). Overall, 26.8 percent of 

operations semen tested bulls and 15.6 percent of 

operations performed scrotal measurement. 

United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

0 20 40 60 80

200 or more

100-199

50-99

1-49

Percent

Procedure

Semen test

Scrotal

measurement

Culture for trich

(Tritrichomonas

fetus)

18.1

41.7

51.6

61.1

10.1

24.4

30.2

41.8

7.5

12.1

15.5

25.4

Herd Size

(Number of Beef Cows)

Figure 2. Percentage of Operations that Performed the Following 

Reproductive Procedures on Bulls* in Preparation for the Last 

Breeding Season, by Herd Size

*Bulls that had been on operation for at least the last two breeding seasons and excluding bulls purchased, 

 leased, or borrowed.

Of the 30.7 percent of operations that 

purchased, leased, or borrowed bulls for the last 

breeding season, 71.3 percent semen tested at 

least some of these bulls. 

Tritrichomonas fetus 

Tritrichomonas fetus (T. fetus)—of which bulls 

are the primary carrier—is a sexually transmitted 

protozoon that causes early embryonic loss in 

cattle and, therefore, prolonged calving seasons. 

Once infected, a female can transmit the protozoon 

to other bulls during breeding but will usually clear 

the infection by the next breeding season. Older 

bulls are more likely to be chronic carriers. Young 

bulls can sometimes clear the infection. 

Critical strategies to prevent T. fetus infections 

include maintaining a closed cow herd, purchasing 

virgin bulls, and testing nonvirgin bulls. Only 9.8 

percent of operations cultured bulls for T. fetus, and 

just 18.5 percent of bulls were cultured for T. fetus

in preparation for the last breeding season; 35.1 

percent of operations that purchased, leased, or 

borrowed bulls in preparation for the last breeding 

season cultured bulls. Additionally, 53.3 percent of 

operations that purchased, leased, or borrowed a 

bull, added bulls that were more than 18 months of 

age or no longer considered virgin, but only 34.4 

percent of those operations cultured all these bulls 

for T. fetus. 

Summary 

Breeding management decisions are key to the 

production and profitability of cow-calf operations. 

Data from this study suggest that there may be 

areas in which producers can improve the 

operations efficiency and reduce its disease risk 

through better bull management. 

________________________________ 

For more information, contact: 

USDA:APHIS:VS:CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov 

#N541.0209 

____________________________________ 

The U.S. Department of Agriculture (USDA) prohibits 

discrimination in all its programs and activities on the 

basis of race, color, national origin, age, disability, and 

where applicable, sex, marital status, familial status, 

parental status, religion, sexual orientation, genetic 

information, political beliefs, reprisal, or because all or 

part of an individual’s income is derived from any public 

assistance program. (Not all prohibited bases apply to 

all programs.) Persons with disabilities who require 

alternative means for communication of program 

information (Braille, large print, audiotape, etc.) should 

contact USDA’s TARGET Center at (202) 720–2600 

(voice and TDD). To file a complaint of discrimination, 

write to USDA, Director, Office of Civil Rights, 1400 

Independence Avenue, S.W., Washington, D.C. 20250–

9410, or call (800) 795–3272 (voice) or (202) 720–6382 

(TDD). USDA is an equal opportunity provider and 

employer. 

Mention of companies or commercial products does not 

imply recommendation or endorsement by the USDA 

over others not mentioned. USDA neither guarantees 

nor warrants the standard of any product mentioned. 

Product names are mentioned solely to report factually 

on available data and to provide specific information.