Genetic parameters of racing merit of thoroughbred horses in Poland

Abstract

Summary The study aimed at estimating variance components of racing ability traits in thoroughbred horses as a contribution to defining the breeding objective for this breed. Data collected were 12 143 placings at finish (square root) and 8641 earnings (log) won by 1414 horses running in 1693 races over the period of 1998–2001. Age of horses ranged from 2 to 5+ years, and the distances were from 1000 to 3200 m. Horses were from 11 state stables, from private breeders (one collective group), and from foreign breeding (another collective group within the factor ‘breeder’). Variance components were estimated by the residual maximal likelihood (REML) method. Statistical analysis accounted for fixed effects of year, age, race, breeder (optional), sex, weight carried and distance, and for the random effects of rider, permanent environment, and animal additive genetics. Pedigrees were at least three generations deep. When breeder effect was excluded from the model, heritability coefficients were 0.12 and 0.18, repeatability 0.23 and 0.34 for earnings and placings at finish, respectively.