Estimation of Genetic and Phenotypic Variance Components for Body Weight Traits of Moghani Sheep using Gibbs Sampling Approach

In this study for prediction of the (Co)-variance components and genetic and phenotypic parameters for growth traits of Moghani sheep, data from birth weight (7368 records), weaning weight (5892 records), 6-month weight (5110 records), 9-month weight (2912 records) and yearling weight (2893 records) were used.  Data was collected during 1995-2017 from Moghani sheep breeding station in Jafarabad of Moghan. (Co) variance components and genetic parameters were estimated by Bayesian statistical method based on Gibbs sampling technique, because of high accuracy of bayasian method. Environmental factors such as birth year, birth season, Sex of lamb, birth type and mother's age were significant on all traits (P<0.01 and as fixed effects in the mode. Age of lamb during weaning was used as covariate in the model. Based on lowest AIC for birth weight, weaning weight, 6-month weight, 9-month weight and yearling weight the direct heritability was found to be 0.35±0.003, 0.20±0.004, 0.23±0.002, 0.36±0.004 and 0.24±0.003 for the traits, respectively. Maternal heritability of birth weight and weaning weight were 0.26±0.002 and 0.11 ±0.002, respectively. The results revealed by increasing lamb's age and reducing lamb's dependence on mother, the contribution of maternal effects to direct genetic effects decreases. Therefore, the importance of this effect was reduced by increasing age due to decreased dependenc if lamb to mother. Low to moderate heritability of the traits indicated that selection for these traits will result in a low to moderate genetic improvement.