Maternal genetic additive variability of conformation traits in half-bred horses

Direct and maternal additive genetic variances as well as covariances between these effects were estimated via derivative-free restricted maximum likelihood algorithm under an animal model. 2750 half-bred mares from four Studs were recorded. The following three traits were analysed: height of wither, circumference of chest, circumference of canon. The breed group, year of birth and place of birth were included as fixed effects. The computations were performed using two genetic models (with and without maternal effects). Direct additive heritability estimates were 0.539 for height of wither, 0.345 (and 0.442 from maternal model) for circumference of chest and 0.233 for circumference of cannon. Using the likelihood ratio test it was concluded that the maternal effects were significiant for the analysed traits. Generally, negative correlation estimates between direct and maternal genetic effects were found for single traits.