Deaths of Standardbred racehorses examined in a Canadian study tended to reflect what researchers describe as a continuum of circumstances rather than a single fatal event.
Their study highlighted a range of factors that contribute to the likelihood of death.
“Though occurring frequently, musculoskeletal injury was less frequent than all other presenting problems combined,” University of Guelph researchers reported in the journal Animals.
For their study, Peter Physick-Sheard, Amanda Avison and William Sears delved into the data contained in a registry of racehorse mortalities which Ontario authorities have required since 2003.
The database, they said, provided opportunities to better understand losses and contributing factors in Standardbred deaths.
“Fatalities occur on and off racetracks, involving welfare concerns, economic impact, and damage to racing’s public profile and social license,” they said.
“Musculoskeletal injury, the most visible loss, represents only one source and remains poorly understood, while for other losses and off-track mortality little is known.”
The study team looked at factors surrounding 978 Standardbred deaths recorded in the Ontario Racehorse Death Registry between 2003 and 2015.
Race and qualifying data for official events and formal workouts (there were 1,778,330 in all) were also gathered. The study team was aided by the findings of post mortem examinations carried out in 55% of the fatalities.
Analysis showed that sex, age, and the workload volume (in particular cumulative workload), as well as the intensity of work, were strongly associated with mortality.
The mortality rate decreased with age, suggesting a survivor effect for older horses and highest mortality odds for young horses. Sex was also influential, with stallions having consistently high odds of mortality.
Looking at the sex-age interaction, the difference was greatest between young geldings (low liability) and young stallions (high liability), with this difference reversing with increasing age.
Females and geldings both experienced increasing mortality odds as they aged when compared with stallions.
Track class, race versus qualifying performance, and outcomes (finishing positions, scratchings, or failure to finish) also affected mortality odds, which increased as performance slowed.
“Intense competition at higher performance levels and qualifying races at lower levels carried particularly high odds.”
The researchers said industry structure contributed to deaths through the interaction between horse characteristics and the competition environment.
Deaths, they said, tended to reflect what they described as a continuum of circumstances, the cumulative impacts of which might be able to be identified before a fatal event occurs.
In essential terms, deaths in the study population had a broad association with frequency, intensity, and quality of work, as well as performance history, age, and sex.
“Mortality,” they said, “is not an inevitable outcome of racing and may represent the endpoint of a continuum of influences whose effects might be anticipated.”
Circumstances that affect the likelihood of death may reflect interaction between intrinsic horse characteristics (their profile and performance) and the competitive environment, and problem-specific triggers by which the combined effect of stressors and chance events cause a specific clinical episode.
“Triggers may be difficult to identify, enumerate, control or foresee, and may masquerade as seemingly benign circumstances.”
Other underlying factors, once recognized, might be manipulated, managed or pre-empted to minimize liability to adverse outcomes when a trigger is encountered.
“Circumstances that appear to carry particularly high odds, such as intense competition and frequent need to requalify, should receive particularly close attention,” they said.
“Analysis suggests that at these levels, while recognizing we have much to learn concerning specific triggers, we may already have significant components of the information required to have an impact on mortality and possibly morbidity (disease) as well.”
The authors stressed that the immediate circumstances behind any specific death should be seen as separate from what they described as the underlying environmental liability.
“This has implications for how future research might be conducted and findings interpreted.
“It is hoped the present study can be used to decrease mortality and cumulative injury so as to reduce losses and strengthen societal support for racing.”
Sixteen Standardbred tracks were active in Ontario during the study period.
The study team noted that horses are the industry’s primary resource and are costly to prepare and maintain.
Horses at risk could perhaps be identified by tools such as performance profiling, with their deaths prevented. “The same approach could be applied to identify horses most in need of withdrawal from competition.”
Physick-Sheard, P.; Avison, A.; Sears, W. Factors Associated with Mortality in Ontario Standardbred Racing: 2003–2015. Animals 2021, 11, 1028. https://doi.org/10.3390/ani11041028