Estimation of Genetic and Environmental Parameters Affected Pre-Weaning Traits of Arabi Lambs
In this study, the data of Birth Weight (BW), Weaning Weight (WW) and Average Daily Gain from birth to weaning (ADG) of Arabi lambs were used to estimate of environmental effects, heritability, phenotypic and genetic correlations among these traits. The parameters were estimated using derivative free restricted maximum likelihood methods by excluding or including maternal genetic or maternal permanent environmental effects to optimize the model for each trait. Influencing factors such as type of birth, year of birth, lambs sex and age of dam were investigated as the fixed effects for models. The results showed that year of birth, type of birth, lambs sex and age of dam were highly significant sources of variation on mentioned traits (p<0.001). On the basis of log likelihood ratio test results, model 1 which included direct genetic effects only was determined to be the most appropriate model for above traits. Direct genetic heritability of BW, WW and DG were 0.12±0.07, 0.10±0.07 and 0.10±0.08, respectively. Phenotypic and genetic correlations between BW-WW, BW-ADG and WW-ADG were 0.23 and 0.49, 0.12 and 0.43 and 0.67 and 0.89, respectively.