Estimation of genetic parameters of Thoroughbred racing performance in the Czech Republic

Abstract

The aim of this study was to estimate the breeding value of English Thoroughbreds in the Czech Republic using racing results from a 22-year period (1980-2001). The data include the performance of two and three-year-old horses which raced in flat races at hippodromes in the Czech Republic. The racing results (30 203) were available corresponding to 6 333 horses descending from 762 sires and 2 836 dams. Different criteria were applied in order to analyse the performance: Log of earnings per race, a normalized ranking value, distance of the race when placed, earnings and number of starts for 2, 3, 2+3 year-old horses. After preliminary studies, a year effect or a sex by year effect was finally retained. Variance component estimation using VCE software gave the following values for heritability (±standard errors): 0.14 ± 0.01 and 0.16 ± 0.01 for the Log of earnings per race and the ranking value. Repeatability was 0.31 and 0.35, respectively. The maternal environment component was evaluated as 0.02 ± 0.004 for the Log of earnings per race and 0.03 ± 0.004 for the ranking value. We found that the Log of earnings per race and the ranking value were two appropriate criteria when taking into account racing performance in selection for Thoroughbreds in the Czech Republic. The genetic correlation of the two criteria was 0.98 ± 0.003. The heritability for the distance when placed was 0.18 ± 0.01. The genetic correlation of the Log of earnings per race and distance was medium, 0.38 ± 0.05 and of the same order, 0.39 ± 0.05 for ranking value and distance. In the case where we used the Log of annual earnings and the number of starts, the heritabilities were for the Log of earnings: 0.15 ± 0.03 for two-year-olds, 0.34 ± 0.03 for three-year-olds and 0.32 ± 0.03 for two and three-year-old careers together and respectively, 0.12 ± 0.03, 0.21 ± 0.03 and 0.20 ± 0.02 for number of starts. The genetic correlations between the earnings and the number of starts were respectively: 0.26 ± 0.14, 0.33 ± 0.06 and 0.19 ± 0.07. The genetic correlation between the number of starts for two and three year-olds which was restricted to horses earning money for two consecutive years, was average: 0.35 ± 0.05 and between earnings for the same ages was high 0.80 ± 0.04.