Genetic parameters of racing merit of Thoroughbred horses in steeplechase races

The aim of this study was to estimate variance components of racing ability in Thoroughbreds involved in steeplechase races. Race results were collected from steeplechase races in France (n=9041), in the United Kingdom and Ireland (n=8314) and contained the results of overall 106 020 runs from 1998 to 2003. Performance was measured by two criteria: earnings and ranks after mathematical transformation. The effects of year, sex, age, and race were considered as fixed, animal, permanent environment and maternal as random. Maternal environmental component for ranks were 0.021 in France and 0.000 in the United Kingdom and Ireland. Estimated heritabilities for the ranking criteria were 0.18 (repeatability 0.33) in France and 0.06 (repeatability 0.19) in the United Kingdom and Ireland. The high genetic correlation between the two traits (0.94 and 0.97) gives the opportunity to find out the most suitable criteria for breeding value estimation.