Estimation of the heritability of lameness in standardbred trotters.

The degree of lameness of 265 randomly selected three-year-old standardbred trotters was assessed on a fixed point scale with 0 indicating soundness and 5 indicating that the animals were not weightbearing. Two variables were used to describe the signs of lameness; one was the continuous variable: the sum of the initial lameness score and the lameness scores after separate flexion tests of the carpal, stifle/tarsal and phalangeal joints and the second was the bivariate variable; the ratio of lame/sound horses. The mean (sd) heritability of the continuous variable was estimated to be 0.25 (0.21), and the model was significant (P = 0.05) with a determination coefficient of R2 = 0.14. For the bivariate variable, lame/sound, the heritability was estimated to be 0.33. The breeding values for the 16 sires in the analyses ranged from 72.2 to 130.5. No influence of gender on the prevalence of lameness was detected.