The genetic parameters of racing success and longevity in the New Zealand Thoroughbred racing industry

ABSTRACT Within the Thoroughbred industry, individual success can be measured with races and prize money won. At an industry level, there is a requirement for horses to be able to race from a young age and have a sustained injury‐free career. Therefore, the variance components of such traits were investigated within ASReml for 26,920 New Zealand Thoroughbred racehorses. Age at first competitive high‐speed event (trial or race start) had high heritability ( h 2 = 0.52 ± 0.02), and an inverse genetic correlation with career earnings (−0.40 ± 0.05) and number of wins (−0.35 ± 0.06). Career earnings ( h 2 = 0.24 ± 0.02) had positive genetic and phenotypic correlations (0.59 ± 0.004) with career length, implying that racing success could be a useful selection proxy for career length. Horses that started earlier had longer career length (−0.21 ± 0.07, – 0.18 ± 0.01). The low heritability of career length (0.11 ± 0.01) reflects considerable environmental influence on this trait, reinforcing the importance of early training and exercise in increasing career length. Therefore, the optimal strategy is a selection programme focusing on racing success, which improves commercial appeal and is genetically correlated with longevity. A training and racing programme that encourage an early competitive high‐speed event would optimise the phenotypic development of the musculoskeletal system and reduce injury risk.