The Reporting of Racehorse Fatalities in New Zealand Thoroughbred Flat Racing in the 2011/12–2021/22 Seasons

SIMPLE SUMMARY: Race day fatalities, associated with fracture and suspected cardiac failure, represent a significant welfare concern. To reduce race day fatalities, data are needed to determine the risk factors under New Zealand racing conditions. The aim of this study was to examine race and horse-level risk factors for race day fatalities in New Zealand Thoroughbred flat racing using retrospective race day data from the 2011/12–2021/22 racing seasons. Horse and race-level factors associated with fatality within 72 h of racing were identified by merging fatality data with master race data for the corresponding seasons. The incidence of fatalities was low and most fatalities were the result of euthanasia due to fatal fracture. Horses which raced over greater distances were more likely to sustain a fatal fracture than horses racing ≤1600 m. Male horses and firmer track conditions were also associated with an increase in the risk of fatal fracture. Horses aged 5 years and older were more likely to die from heart failure than younger horses. The shift in the reporting system to an online app resulted in a greater level of detail provided for fatality events, enabling the identification of specific risk factors. ABSTRACT: Race day fatalities as a consequence of catastrophic musculoskeletal injury and cardiac failure are both a welfare concern and provide a challenge for the social perceptions of equine welfare within the racing industry. To reduce race day fatalities, the risk factors under New Zealand racing conditions need to be identified. The aim of this study was to examine race and horse-level risk factors for fatalities in New Zealand Thoroughbred flat racing using retrospective race day data from the 2011/12–2021/22 racing seasons. Horse and race-level factors associated with a suspected cardiac failure and fatal fracture were identified by merging fatality data with the master race dataset for the corresponding seasons. Most fatalities were associated with fatal fracture (0.4 per 1000 starts, 95% CI 0.4–0.5). Horses which raced over distances > 1600 m were 1.7 times (95% CI 1.2–2.5) more likely to sustain a fatal fracture than horses racing ≤ 1600 m. Male horses and firmer track conditions were also associated with an increase in the risk of fatal fracture. Horses aged 5 years and older were 2.1 (95% CI 1.1–4.6) times more likely to suffer a suspected cardiac failure than younger horses. Changes in the industry reporting system improved the level of detail provided for fatalities, enabling the identification of specific risk factors.