Description of veterinary events and risk factors for fatality in National Hunt flat racing Thoroughbreds in Great Britain (2000-2013).

BACKGROUND: No large-scale studies have described veterinary events occurring in National Hunt (NH) flat racing or investigated risk factors for fatality in this race type.

OBJECTIVES: To describe injuries and conditions requiring veterinary attendance on race day and to determine risk factors for racehorse fatality in NH flat racing in Great Britain.

STUDY DESIGN: Retrospective cohort study (2000-2013).

METHODS: Information from all NH flat races held over the study period, including horse, race and veterinary event report details, was combined. Veterinary events were described by type and anatomical structure(s) affected. Incidence per 1000 starts were calculated for all veterinary events and by event group, and stratified by certain horse- and race-level variables. Risk factors for fatality were determined using multivariable logistic regression modelling.

RESULTS: Over the 14-year study period, 544 veterinary events were recorded, providing an overall incidence of 13.0 events per 1000 starts. The most common events were bone injuries (23.5%) and tendon or ligament injuries (16.4%). A fatal outcome was recorded for 117 horses (21.5% of all events), resulting in an incidence of 2.9 deaths per 1000 starts. Odds of fatality were 4.33 (95% confidence interval [CI] 1.59-11.82; P = 0.02) times higher in races restricted to conditional jockeys compared to those that were not. Horses starting in their first race experienced 1.44 (95% CI 1.00-2.08; P = 0.05) times the odds of death compared to those that had raced before.

MAIN LIMITATIONS: Classification of veterinary events frequently relied upon presumptive diagnosis.

CONCLUSIONS: This study provides a benchmark for the ongoing surveillance of veterinary events in NH flat racing. These results support the phasing out of NH flat races restricted to conditional jockeys and highlight the need for further work to establish why NH flat racing Thoroughbreds competing in their first race are at increased risk for death.