Genetic parameters of racing performance on Thoroughbred horses in Hungary
The study aimed the estimation of variance components of racing ability traits in Thoroughbred horses. Collected data consisted of 1486 2−3−4-years-old general handicap weights (GHCP), 30 807 runs, 20 040 placings at finish, 16 605 earnings (log) won by 1 890 horses running in 3 316 races over the period of 1996–2004. Age of horses ranged from 2 to 12 years, and the distances varied from 1 000 to 3 200 m. Variance components were estimated by the residual maximal likelihood (REML) method. Statistical analysis accounted for fixed effects of year, age, race, sex, weight carried, trainer, jockey, ground and distance, and for the random effects of jockey, permanent environment, and additive genetic effects. Pedigrees were at least six generations deep. When trainer or rider effect was excluded from the model, heritability coefficients for earnings were 0.109 and 0.108 (repeatability 0.224 and 0.227), heritability for placings at finish were 0.059 and 0.059 (repeatability 0.142 and 0.14 respectively). Estimated heritabilities on the hendicap weights were high, 0.562 for the three-years-old, 0.661 in the and 0.663 for the four-year-old horses respectively.