Effect of different animal models on estimate of genetic parameters and trends of some growth traits for Baluchi sheep

In this research, a data set comprising 35,511 pre-weaning growth records belonging to 11,837 lambs (6,030 males and 5,807 females) resulted from 300 rams and 3,694 ewes and collected during 1986-2008 from two flocks of Abbas Abad Breeding Centre, Mashhad was used. Based on inclusion of direct additive genetic (model 1), direct additive genetic and maternal permanent environment (model 2), two above components along with maternal additive genetic and without covariance (model 3), and with taking account of covariance (model 4), genetic parameters were estimated. Based upon the best model, C2, direct and maternal heritabilities for birth weight were 0.081, 0.104 and 0.072, respectively. The corresponding figures for weaning weight were 0.073, 0.063 and 0.025, respectively and for daily gain were 0.068, 0.046 and 0.014, respectively. Genetic trends for the traits were found to be 2.688 (±0.104), 7.208 (±0.359) and 0.069 (±0.004) g per year, respectively and statistically significant (P<0.01) indicating that positive favorable changes have been resulted from selection in the population under consideration.