Risk factors for the elimination of endurance horses from competition

Objective-To identify risk factors such as signalment, previous competition miles completed, ride characteristics, and physical examination variables associated with the elimination of horses during endurance competitions. Design-Retrospective observational study. Sample-Veterinary records for 3,493 endurance horse competition starts. Procedures-Records were requested of all sanctioned 2007 endurance horse competitions in the United States. Only rides that provided data from all horses were included. The horse's signalment, previous endurance competition record, specific ride characteristics, weight division (ie, based on rider's weight with tack), and physical examination variables throughout the ride were included for analysis. Examination variables were separated into abnormalities occurring prior to the start of the ride, during the first half of the ride, and during the second half of the ride. Multivariate logistic regression was used to identify risk factors for overall elimination and elimination subcategories (lameness and metabolic). Results-Specific breeds, the heavyweight division, and distance of the ride were all associated with an increased risk of elimination. A variety of examination variables prior to the start of the ride and during the ride were associated with elimination and included heart rate, cardiac recovery index, and abnormal gastrointestinal sounds. Conclusions and Clinical Relevance-Results suggested that specific risk factors were associated with elimination of horses from endurance competitions. These factors may be used to help identify horses at higher risk for elimination and prevent morbidity associated with competition. (J Am Vet Med Assoc 2011;239:493-498)