Adjustments for variability and their impact on heritability estimates of the earnings of Banei racing horses

Abstract

Here, we examined the impact of adjustments of variability on heritability estimates of the earnings of 2-year-old Banei racing horces. Data of 2302 Banei racing horses born in the period 2005-2014, and the pedigree records of 27,215 animals were used in our statistical analyses. The records of Banei racing horses contained sex, year and month of birth, date of performance testing, and earnings at 2 year of age. The variability of earnings at 2 years of age was adjusted by log-transformation or stratification into 3, 5 or 7 classes. An animal model that included sex, birth year, and age at the time of performance testing as fixed effects, and additive genetic effects and residuals as random effects, was used to estimate genetic parameters. Age at the time of performance testing was estimated by using the date of the performance testing and the birth month. The heritability estimates of log-transformed earnings (0.29) was higher than that of untransformed earnings (0.16). The heritability estimates when earnings were stratified into 3, 5, or 7 classes were in the range 0.32-0.36. Thus, the present results suggest that higher heritability estimates are obtained when the variability of earnings is adjusted.