Risk factors for racehorse fatalities identified in British study

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Risk factors for Thoroughbred racehorse fatalities in Britain have been explored in a study, with firmer going and increasing race distance found to increase the chances of death.

Improving horse performance, the first year of racing and wearing eye cover for the first time were also found to increase the odds of a fatality.

Sarah Rosanowski and her colleagues, writing in the peer-reviewed journal PLOS ONE, said a key focus of the racing industry is to reduce fatalities.

The study team analysed data relating to horses participating in flat racing in Great Britain between 2000 and 2013.

Information on the horses, the races and the courses were combined with all race-day fatalities recorded by racecourse veterinarians in a central database.

The researchers looked at all starts, as well as separating out those on turf surfaces for separate analysis.

There were 806,764 starts in total, of which 548,571 were on turf, with 610 fatalities in total. This represented a fatality incidence of 0.76 per 1000 starts.

Of the 610 fatalities, 377 (61.8%) occurred on turf.

In both analyses, increased track firmness, increasing racing distance, increasing average horse performance, first-year racing and wearing eye cover for the first time all increased the odds of fatality, the researchers reported.

“Generally, the odds of fatality also increased with increasing horse age whereas increasing number of previous starts reduced fatality odds.”

When looked at all starts, horses racing in an auction race were 1.46 times were more likely to die compared with horses not racing in this race type. Auction races are restricted to horses sold or bought  under the hammer at specified sales.

When looking at turf starts only, horses racing in Group 1 races were at 3.19 times more likely to die than horses not entered in this race type.

In total, 205 trainers (16.8%) had horses that experienced a race-day fatality on turf. Sixty-two percent of these (127) had one fatality, 20.5% (42) had two fatalities and 11.7% (24) had three or four fatalities.

One trainer had more than 10 fatalities over the 14-year study period.

Discussing their findings, the researchers said: “Regardless of race type, horses with higher average performance scores (i.e. better performing horses) had an increased risk of fatality.”

They said the association between horse age and race-day fatality had been identified previously, with studies identifying increasing risk with increasing age at which a horse started racing.

“While age-related variables (age at first start, current age or years in racing) have been included in most race-day risk factor models, few have included variables to account for both the current age of the horse and the age at which they started racing.

“The current study, rather than providing conflicting evidence regarding the effect of age on the risk of race-day fatality, through the inclusion of first year racing, adds growing evidence regarding the complexity of age as a risk factor for race-day fatality.”

The importance of career length and the age or stage that horses start racing, as well as the role of  bone microdamage, which can lead to failure, have been noted previously.

“Regardless of the firmness of the going or whether the start was held on a turf or an all-weather surface, racing in summer or autumn had the highest risk of fatality. This is similar to previous studies, where racing in summer was identified as increasing the risk of superficial digital flexor tendon injury in jumping horses and increasing the risk of sudden death.

“It is possible that changes to the ground surface, which may not be accurately measured by the official race going, may occur during the summer and autumn months, increasing the likelihood of fatality.

“However, this is unlikely to be the complete picture.

“Firstly, the flat racing season runs from April until early November, with few races held in winter. Thus, the risk of fatality increased with the progression of the racing reason.

“This could be because trainers may be under more pressure to race previously unraced or lightly-raced horses before the end of the racing season, with such horses being more prone to racing injury because of underlying issues that prevented them from racing earlier on in the season.

“Additionally, potential seasonal changes in training surfaces and increased time in training and/or training intensity for horses racing later in the flat racing season could play a role. It was not possible to take account of such factors in the current study, as training data are not routinely collected.”

They concluded: “This study has identified specific and, in some cases, potentially modifiable risk factors for fatality in flat racing in Great Britain.

“Previously identified risk factors of going, race distance and age, plus novel risk factors of eye cover and race type are important risk factors for the occurrence of race-day fatality in flat racing Thoroughbreds.

“The results from this study will help to inform intervention strategies aimed at further reducing the rate of fatality in flat racing horses, enhancing horse and jockey welfare and safety.”

The study team comprised Rosanowski, from the City University of Hong Kong; Yu-Mei Chang and Kristien Verheyen, both from Britain’s Royal Veterinary College; and Anthony Stirk, from the British Horseracing Authority.

Rosanowski SM, Chang Y-M, Stirk AJ, Verheyen KLP (2018) Risk factors for race-day fatality in flat racing Thoroughbreds in Great Britain (2000 to 2013). PLoS ONE 13(3): e0194299. https://doi.org/10.1371/journal.pone.0194299

The study can be read here

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