Association between the administration of phenylbutazone prior to racing and musculoskeletal and fatal injuries in Thoroughbred racehorses in Argentina.

OBJECTIVE: To examine the association between prerace administration of phenylbutazone and the risk of musculoskeletal injury (MSI) and fatal injury in Thoroughbred racehorses that raced between 2006 and 2015 at 2 of the 4 official racetracks in Argentina. SAMPLE: Data from racetrack databases and veterinary reports on 283,193 race starts. PROCEDURES: Data were collected relating to race performance and injury outcomes for starts at these tracks. The incidence of MSI and fatal injury was calculated for each year, stratified by the declared prerace administration of phenylbutazone. Univariable logistic regression, followed by multivariable logistic regression, was used to identify significant risk factors for both MSI and fatal injury. RESULTS: Analyses identified associations between the declared prerace administration of phenylbutazone and the risk of MSI and fatal injury during racing. Horses with declared prerace phenylbutazone administration had greater odds of MSI (OR, 1.45 [95% CI, 1.03 to 2.04]) and fatal injury (OR, 1.59 [95% CI, 1.1 to 2.27]) than did horses racing without prerace phenylbutazone administration. These associations remained significant when other risk factors were accounted for in both multivariable models. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested an association between the prerace administration of phenylbutazone and the risk of MSI and fatal injury in Thoroughbred racehorses during racing. Although these results did not imply a direct causal relationship between prerace phenylbutazone administration and injury, they may be considered in the development of more conservative medication policies to optimize racehorse welfare in North and Latin America.

Risk factors associated with fatal injuries in Thoroughbred racehorses competing in flat racing in the United States and Canada.

OBJECTIVE To identify risk factors associated with fatal injuries in Thoroughbred racehorses in the United States and Canada. DESIGN Retrospective study. ANIMALS 1,891,483 race starts by 154,527 Thoroughbred racehorses at 89 racetracks in the United States and Canada from 2009 to 2013. PROCEDURES Data were extracted from the Equine Injury Database, which contained information for 93.9% of all official flat racing events in the United States and Canada during the 5-year observation period. Forty-four possible risk factors were evaluated by univariate then multivariable logistic regression to identify those that were significantly associated with fatal injury (death or euthanasia of a horse within 3 days after sustaining an injury during a race). RESULTS 3,572 race starts ended with a fatal injury, resulting in a period incidence rate of 1.9 fatal injuries/1,000 race starts. Twenty-two risk factors were significantly associated with fatal injury. Risk of fatal injury was greater for stallions than for mares and geldings and increased as the number of previous nonfatal injuries and race withdrawals and level of competitiveness (eg, horse's winning percentage and race purse) of the horse or race increased. CONCLUSIONS AND CLINICAL RELEVANCE Results identified several risk factors associated with fatal injuries in Thoroughbred racehorses. This information can be used as a guideline for the identification of racehorses at high risk of sustaining a fatal injury and in the design and implementation of preventative measures to minimize the number of fatal injuries sustained by horses competing in flat racing in the United States and Canada.