High workload among risk factors for Thoroughbred fatalities in Ontario – study

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Injury risk was found to be higher in workouts for horses switching from dirt/synthetic to turf racing.
Injury risk was found to be higher in workouts for horses switching from dirt/synthetic to turf racing. Photo by Thomas Hawk

Risk factors for Thoroughbred deaths in Ontario racing include a high workload and their stage of training, researchers report.

The Canadian province’s Alcohol and Gaming Commission records racing fatalities through its Equine Health Program.

University of Guelph researchers Peter Physick-Sheard, Amanda Avison and William Sears set about examining all Thoroughbred fatalities from 2003 to 2015 to identify associations.

Official records and details of fatalities were combined in modelling of 236,386 Thoroughbred race starts for 433 fatalities (within 60 days), and 459,013 workouts for 252 fatalities within the same 60-day window.

Fatality rates were found to be 2.94 per 1000 race starts (all fatalities) and 1.96 per 1000 starts (breakdowns only), with an overall rate of 2.61%, or 26.1 fatalities per 1000 horses.

Musculoskeletal injury was the most common cause and there was a high incidence of horses dying suddenly, the trio reported in the journal Animals.

“Liability was high for young horses early in the season with a differential according to sex and whether a male horse was gelded.”

Horses undertaking repeated workouts had a higher risk, and the risk was also found to be higher in workouts for horses switching from dirt/synthetic to turf racing, and for young horses in sprints.

Race distance was not a significant factor, but high fatality rates were seen in some distance races with large fields, combined with effects of age and workload.

As field size increased, so did the fatality risk for early-finishing horses.

“Findings suggest jockey strategy could be an important factor influencing fatalities,” the study team wrote.

“Findings indicate that rapid accumulation of workload in animals early in their preparation is likely to be damaging,” they reported.

The fatality rate fell toward the end of a season and for horses with a long career history of successful performance. However, horses not exhibiting this robustness and staying power represent the population of greatest concern.

Fatality rates were found to be 2.94 per 1000 race starts (all fatalities) and 1.96 per 1000 starts (breakdowns only), with an overall rate of 2.61%, or 26.1 fatalities per 1000 horses.
Photo by mjsmith01

Comparison with published reports reveals Ontario’s Thoroughbred fatality rates to be high, they said.

“There is no single explanation. Here, as in previous studies, musculoskeletal injury was the predominant complaint, but horses dying suddenly was also a frequent complaint.”

The findings, they said, present opportunities for intervention. Higher risks for horses switching from dirt/synthetic to turf racing and for young horses engaged in short-distance sprints present additional targets, they added.

“Though the impact of race distance appears limited, high mortality in some large field races, when combined with effects of age and workload, identify circumstances where horses might be at particular risk. Large races run at distance tend to be feature races, and fatalities particularly noticeable.”

The authors said the relationships between field size, finish position, and fatality are complex, but provide additional insights into possible causes of death and focus for intervention.

“Horses undertaking repeated workouts appear to have a higher liability, suggesting ongoing problems and a need for closer monitoring. Evidence jockey strategy could be a contributing factor in fatality reveals the need for further study.”

The study team said they could not confirm a specific impact of training, but results suggest rapid accumulation of workload in animals in early preparation is likely damaging.

“Though fatality appears to fall toward the end of a season and for horses with a long career history of successful performance, it is horses that do not exhibit this robustness and staying power that represent the population of greatest concern in reducing fatality.

“If identified associations represent sources of stress, current or cumulative, then identifying at-risk animals on this basis may be as productive as targeting specific, discrete mechanisms suspected to be causative.

“It will be up to the industry and regulators to decide what aspects, if any, of this study’s findings they wish to incorporate.”

Handling and management of young horses and the impacts of sex may require fundamental changes in the industry at many levels, they said.

“Close monitoring of musculoskeletal function, evaluating horses in greater depth before they work or race, and ensuring injured horses are recovered before return to work, applied as extensions to the close monitoring many trainers already apply, might be more rapidly adopted, but have manpower and resource dimensions.

“Achieving a better understanding of reasons for horses dying suddenly, though urgent, likely has a long horizon.

“Specifics aside, many industry members are already concerned by injury and fatality levels and welcome industry-wide initiatives acknowledging and addressing the problem. Clearly, we need to know more.”

Physick-Sheard, P.; Avison, A.; Sears, W. Factors Associated with Fatality in Ontario Thoroughbred Racehorses: 2003–2015. Animals 2021, 11, 2950. https://doi.org/10.3390/ani11102950

The study, published under a Creative Commons License, can be read here.

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