Estimation of genetic parameters of autosomal and sex-linked pre-weaning traits in Makuie sheep using multivariate analysis

Abstract

The objective of this study was to determine the genetic parameters of autosomal and sex-linked effects for birth weight (BW), weaning weight (WW), average daily gain from birth to weaning (ADG) and kleiber ratio (KR) of Makuie sheep. The data set used in this study was collected at Makuie sheep breeding station in West Azerbaijan province, Iran, between 1994 and 2011. The fixed effects included herd-year, sex (male or female), birth type (single or twin), and age of dam (five classes, 2-6 years old). The three multivariate linear animal models including direct (autosomal and sex-linked) and maternal effects were used to analyze data. The 2nd model (including direct additive genetic effects of animal (autosomal and sex-linked) and permanent environmental effects), with the lowest AIC value was considered as the most appropriate model. Based on the most appropriate fitted model, direct autosomal and sex-linked heritabilities of BW, WW, ADG and KR were 0.12±0.04 and 0.03±0.03, 0.18±0.04 and 0.05±0.03, 0.37±0.04 and 0.04±0.03, and 0.52±0.05 and 0.07±0.04, respectively. The magnitude of sex-linked variances as a proportion of phenotypic variance obtained by the best model were 4%, 4.5%, 3% and 5.7% for BW, WW, ADG and KR, respectively. Also, the autosomal and sex-linked chromosomes, maternal permanent environmental and phenotypic correlations were ranged from -0.20 to 0.96, 0.11 to 0.84, -0.34 to 0.89 and -0.20 to 0.91, respectively. The results of this study indicated that the sex-linked chromosomes have an affect like maternal effects, and it could contribute to a more accurate estimation of the direct autosomal heritability.