The purpose of the study was to estimate the influence of the additive and non-additive genetic effects on the birth weight, using two different crossbreed models. Data on 1176 birth weights were collected. The animals were crosses, with different ratios of Awassi, East-Friesian, Istrian, and Travnik Pramenka sheep breed. The focal breed in this study was Istrian, which is an autochthonous breed in Croatia. In both models mixed procedure was used with random effect of sire and fixed effects of sex, year and month of birth, litter size, and direct inbreeding. The first model contained the additive breed effects, while the second model additionally included non-additive effects of heterosis and recombination loss. Sex, litter size, year and month of birth significantly affected birth weight in both models. Effect of direct inbreeding was negative and significant only in second model. Significant positive additive breed effect was estimated for Awassi breed in both models. The East-Friesian additive breed effect was positive in both models, but it was significant for the first one only. The positive and significant heterosis effect for the birth weight was estimated for the crosses between East-Friesian and Travnik Pramenka, as well as between Travnik Pramenka and Istrian breed. Same crosses showed significant and positive effect of recombination loss. The negative effect of recombination loss was estimated for the crosses of Awassi breed.
- crossbreeding effects
- birth weight