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

Veterinary Services 

Centers for Epidemiology and Animal Health March 2007 

_________________________________________________________________________________________________________________________ 

Trends in Equine Mortality, 

1998–2005 

One priority in the U.S. Department of Agriculture’s 

National Animal Health Monitoring System’s 

(NAHMS) Equine 2005 study was to compare 

changes in the equine industry from 1998 to 2005 

in relation to equine death events. 

For the Equine 2005 study, NAHMS collected 

data on equine health and management practices 

from a representative sample of operations with 5 

or more equids in 28 States within four regions.* 

The 28-State target population represented 78.0 

percent of equids and 78.6 percent of operations 

with 5 or more equids in the United States. 

Interviews were conducted from July 18 through 

August 12, 2005, and 2,893 equine operations 

provided data on equine health and management. 

 Some estimates in this information sheet are 

compared to estimates from Equine ’98, NAHMS’ 

previous study of the U.S. equine industry. For the 

evaluation of changes and trends, the data used to 

generate estimates based on the Equine ’98 study 

were re-analyzed to represent operations with five 

or more equids present on January 1, 1998. 

Therefore, estimates for comparing the 2 study 

periods are based on 3 points of commonality: 

same 28 States, data collection performed by 

National Agricultural Statistics Service 

enumerators, and same reference population of 5 

or more equids. 

 Of operations participating in the Equine 2005 

study, 40.3 percent identified their primary function 

as “farm/ranch” and 37.0 percent identified their 

primary function as “residence with equids for 

personal use.” A resident equid was defined as an 

____________________________________

*Regions: 

West: California, Colorado, Montana, New Mexico, Oregon, 

Washington, and Wyoming

Northeast: New Jersey, New York, Ohio, and Pennsylvania

South: Alabama, Florida, Georgia, Kentucky, Louisiana, 

Maryland, Oklahoma, Tennessee, Texas, and Virginia 

Central: Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, 

and Wisconsin

equid that spent or was expected to spend more 

time at the operation than at any other operation 

during the previous 12 months, whether or not it 

was present at the time of the interview. The 

operation was its home base. 

Participants in the Equine 2005 study were 

asked to provide information on deaths among their 

resident equids during the previous 12 months.

Owner/operators were asked about the number of 

deaths (including euthanasia) and the underlying 

causes of these deaths for three age groups: birth 

to 30 days, 30 days to 6 months, and 6 months and 

older. Cause of death was reported by the 

owner/operator and not necessarily confirmed by a 

veterinarian. 

Foal deaths 

Overall, the percentages of foals born alive that 

died within the first 30 days of life were similar in 

1998 and 2005, 4.2 and 4.9 percent respectively. 

Of these deaths, about half occurred within the first 

2 days of life in both 1998 and 2005 (table 1). 

There was a decrease in percentage of foal deaths 

from 1998 to 2005 attributed to unknown and 

“other” causes (figure 1). 

Table 1. For foals born alive, percentage of foals 

that died in the first 30 days of life (including those 

born on or moved onto the operation) during the 

previous 12 months, by age at death (in days): 

 Percent Foals 

 1998 2005 

Age at Death (Days) Percent Percent 

2 or less 2.0 2.6 

3 to 30 2.2 2.3 

Total 4.2 4.9 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

The difference in other causes of death can 

most likely be attributed to the addition in the 2005 

study questionnaire of two new cause-of-death 

categories: infectious disease unrelated to specific 

body system, blood infection (septicemia); and 

failure to get colostrum or milk from the mare. 

These additions allowed owner/operators to better 

categorize known causes of death and may have 

led to the decrease in deaths reported as unknown. 

Together, the two new cause-of-death categories 

accounted for 18.2 percent of deaths in 2005. 

Unknown causes of death dropped from 33.2 

percent in 1998 to 17.9 percent in 2005. 

 In 1998, other than unknown and other causes 

of death, birth defects accounted for the highest 

percentage of foal deaths (17.6 percent), followed 

by injury/wounds/trauma unrelated to birth (9.4 

percent) and dystocia, trauma, or complications at 

birth (5.1 percent). In 2005, excluding unknown and 

other causes of death, injury/wounds/trauma 

unrelated to birth accounted for the highest 

percentage of foal deaths (18.6 percent), followed 

by failure to get colostrum or milk from mare (14.9 

percent), and dystocia, trauma, or complications at 

birth (10.7 percent) (figure 1). In 1998, “other” 

reported known causes of foal death included 

prematurity, lack of milk or colostrum production by 

mare, exposure, drowning, and infection. In 2005 

“other” known causes of foal death included 

predator attacks and adverse environmental 

conditions. 

Since injury/wounds/trauma is one of the 

leading causes of foal deaths in foals during the 

first 30 days of life, it may be possible to reduce the 

overall percentage of deaths in this age category 

because injury/wound/trauma is a potentially 

preventable cause of death. 

0

10

20

30

40

2005

1998

Dystocia Birth

defects

Injury/

wounds/

trauma

Septi- Other

cemia

Failed 

to get 

colostrum/

milk from mare

Unknown Combined

categories*

Figure 1. For Foals Born Alive, Percentage of Foal Deaths During

the First 30 Days of Life, by Cause of Death and by Year

Percent

5.1

10.7

17.6

8.9 9.4

18.6

NA

3.3

14.9

NA

29.3

13.7

33.2

17.9

5.4

12.0

Cause of Death

*Combined categories include colic (0.2%,1.5%), other digestive (0.6%, 6.4 %),

respiratory (1.5%, 3.6 %), and neurologic problems (3.1%, 0.5 %)

Equid deaths 

Overall, the percentages of equids more than 

30 days of age that died in 1998 and 2005 were 

similar (2.0 and 1.8 percent, respectively). The 

highest mortality rates were found in equids aged 

20 years and or more in both 1998 and 2005 (11.9 

and 10.2 percent, respectively). Mortality rates for 

equids more than 30 days but less than 20 years of 

age were eight to nine times lower than that of 

equids 20 years or older (Table 2). 

Table 2. Percentage of resident equids more than 30 

days of age that died or were euthanized during the 

previous 12 months, by age: 

 Percent Resident Equids* 

1998 2005 

Age at Death Pct. Pct. 

More than 30 days 

but less than 6 

months 1.4 1.2 

6 months to less 

than 5 years 1.5 1.1 

5 years to less 

than 20 years 1.4 1.2 

20 years or older 11.9 10.2 

Total deaths of 

equids more than 

30 days of age 2.0 1.8 

*(Number of resident equids that died or were euthanized) x 100/age 

class of resident equine inventory.
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Overall, for equids more than 30 days to less 

than 6 months of age, the percentages of deaths 

attributed to a specific cause were similar in 1998 

and 2005 (figure 2). Injury/wounds/trauma 

accounted for the highest percentage of deaths 

among these equids in 1998 and 2005. 

Injury/wounds/trauma is a potentially preventable 

cause of death, and lowering the number of deaths 

in this category would decrease the overall 

percentage of deaths among this age group. In 

addition, approximately one in four deaths among 

equids aged more than 30 days to less than 6 

months were attributed to unknown causes in 1998 

and 2005. Identifying a higher percentage of these 

unknown causes would allow owners/operators to 

take precautions that could lead to fewer deaths. 

Colic

Fire/lightening

other storms

Injury/wounds

trauma

Lameness

Liver/kidney

0 5 10 15 20 25 30 35

2005

1998

Other

digestive

Other

known

Combined

categories*

Unknown

7.5

31.8

3.4

NA

7.9

23.9

7.8

8.5

NA

1.1

9.3

8.3

5.8

14.6

9.5

8.9

28.3

23.4

Cause

of Death

Percent

Figure 2. For Equids More Than 30 Days to Less Than 

6 Months of Age, Percentage of Equid Deaths (Including 

Euthanasia), by Cause of Death and by Year

*Includes respiratory (2.8%, 7.3%), neurologic (6.6%, 0.0%), 

reproductive (0.0%, 1.6%), and dystocia (0.1%, 0.0%).

 For equids aged 6 months or older, the 

percentages of deaths were similar in 1998 and 

2005 across all causes of death (figure 3) with the 

exception of “other” known causes of death, which 

was higher in 1998 than in 2005, likely because of 

additional choices added to the 2005 questionnaire. 

Commonly reported causes of death in this age 

category in 1998 and 2005 were old age, colic, and 

injury/wounds/trauma. “Other” known causes of 

death in 1998 included cancer, heart disease, 

poisoning, lightning strike, liver disease, and birth 

defects. In 2005, “other” known causes of death 

included heart attack, snake bite, stroke, ruptured 

vessel, heat stroke, endocrine disease, and pigeon 

fever. 

Colic

Fire/lightening

other storms

Injury/wounds

trauma

Lameness

Liver/kidney

0 5 10 15 20 25 30 35

2005

1998

Other

digestive

Other

known

Combined

categories*

Unknown

Cause

of Death

Percent

Figure 3. For Equids 6 Months or Older, Percentage of 

Equid Deaths (Including Euthanasia), by Cause of Death 

and by Year

*Includes respiratory (3.1%, 2.7%), neurologic (1.8%, 3.3%), 

reproductive (0.5%, 0.9%), and dystocia (1.3%, 2.3%).

NA

2.7 Cancer

Old age

22.2

15.2

NA

2.1

12.7

16.0

6.9

7.7

24.8

30.4

1.3

3.0

NA

1.9

5.8

18.0

6.7

9.2

7.4

5.7

Summary 

A high percentage of death among foals aged 

less than 30 days and equids aged more than 30 

days to less than 6 months was attributed to 

unknown causes in both 1998 and 2005. Identifying 

these unknown causes is an area for further study. 

If the cause of death is found to be preventable, it 

may be possible to prevent future equid deaths. 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

________________________________ 

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 

www.aphis.usda.gov/vs/ceah/ncahs 

#N471-0307 

____________________________________ 

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