Estimation of the autosomal and sex-linked genetic parameters for growth rate and efficiency-related traits in Moghani sheep

In the present study data on growth traits of Moghani sheep breed, collected during 1988 to 2011 at Jafarabad breeding station, were used. The studied traits were average daily gain from birth to weaning (ADG1), average daily gain from weaning to six months of age (ADG2), average daily gain from six months of age to yearling age (ADG3), Kleiber ratio from birth to weaning (KR1), Kleiber ratio from weaning to six months of age (KR2), Kleiber ratio from six months of age to yearling age (KR3), growth efficiency from birth to weaning (GE1), growth efficiency from weaning to six months of age (GE2), and growth efficiency from six months of age to yearling age (GE3). Genetic and phenotypic parameters were estimated for autosomal and sex-linked components of the studied traits under animal model. Direct autosomal heritability estimates for ADG1, ADG2, ADG3, KR1, KR2, KR3, GE1, GE2 and GE3 were 0.09±0.01, 0.07±0.02, 0.03±0.01, 0.13±0.02, 0.09±0.02, 0.02±0.01, 0.07±0.01, 0.06±0.01 and 0.02±0.01, respectively. Pre-weaning studied traits were not influenced by sex-linked additive genetic components. Sex-linked heritability estimates for ADG2, KR2, GE2, ADG3, KR3 and GE3 were 0.04±0.01, 0.02±0.01, 0.02±0.01, 0.02±0.01, 0.02±0.01 and 0.03±0.01, respectively. Autosomal additive genetic correlations between the traits were ranged from -0.68±0.22 for ADG3-KR1 and ADG1-GE2 to 0.99±0.01 for KR3-GE3. Sex-linked additive genetic correlations among the traits were positive and varied from 0.14±0.02 for GE2-ADG3 to 0.98±0.01 for ADG3-KR3 and KR3-GE3. Results revealed that when sex-linked effects are important, genetic analysis using an animal model which accounts for both autosomal and sex-chromosome inheritance provides more accurate estimates of variance components of the studied post-weaning traits.