Ontario Racehorse Death Registry, 2003-2015: Descriptive analysis and rates of mortality.

The study analyses data from the Ontario Racehorse Death Registry between the years 2003-2015 in order to understand patterns and causes of mortality amongst racehorses. The results indicate that the risk and rate of death varied by breed, with Thoroughbreds experiencing the highest risk and rate of death associated with exercise, followed by Quarter Horses, and the lowest being Standardbreds.

Objective and Methods

• The purpose of the research was to understand and quantify mortality in racehorses and pinpoint differences between the breeds. The motivation for this analysis was to provide insights on ways to enhance the welfare of racehorses and possibly reduce the costs associated with participation in horse racing. To do this, the researchers conducted a retrospective annualised cohort study using the Ontario Death Registry, examining data from 2003-2015.
• The researchers reviewed 1713 cases from the registry over this 12-year period. They aimed to determine mortality rates based on breed, year, age, gender and the circumstances of death. They supplemented their data with race and trial data from industry performance databases to establish the relationship between death and official work.

Findings

• Upon analyzing the data, the researchers found differences in mortality rates and individual risk among the different breeds of racehorses. Thoroughbreds had the highest exercise-associated mortality (EAM) rate and risk, followed by Quarter Horses, and finally, Standardbreds with the lowest.
• This mortality rate was not associated solely with exercise however. Non-exercise annual individual risk was actually highest for Standardbreds, as compared to the other two breeds.
• The pattern and type of EAM reflected the specific characteristics of the industry competitive activities associated with each breed. Higher mortality rates for Thoroughbreds and Quarter horses were linked with exercise and involved incidents like musculoskeletal injuries, sudden death and accidents. Standardbreds had lower EAM, reflecting the more extensive nature of training preparation and racing for this breed.

Limitations and Conclusions

• The study did have some limitations. The data available did not provide information on morbidity, mortality beyond the 60-day horizon or for horses not racing. The numbers for the Quarter horses were also relatively small.
• Despite these limitations, the study reached the conclusion that the intensity of race exercises poses a clear hazard for horses, with the level of risk varying according to breed. It was also found that the nature of these risks is closely mirrored by industry cultural and management norms.
• The differences in death rates among different breeds suggest that some mortality could be prevented with different practices, improving the welfare of the horses and lowering the costs of participating in the races.
• A consistent finding, irrespective of breed, was that musculoskeletal injuries were a key contributing factor to mortality among racehorses.