Influence of maternal effects on estimation of genetic parameters of growth traits in Ghezel sheep using bayesian via Gibbs sampling technique

The current study was carried out to estimate maternal effects and to research the influence of this effect on estimate of genetic parameters for growth traits in Ghezel sheep, using pedigree information and body weight records collected from year 1994 to 2010 in Ghezel Sheep Miandoab Breeding Station. The studied traits were body weight at birth and 3, 6, 9 and 12 months of age. (Co) variance components, heritability and maternal effects were estimated by Bayesian via Gibbs sampling technique. The significant test for known effects was carried out by GLM procedure of SAS 9.2 software. The fixed effects of sex, type of birth, age of dam as well as year- season of birth were significant (P<0.05). Genetic parameters were estimated using MTGSAM software by using four different models including or ignoring maternal effects. Based on the results, the full model including environmental and maternal genetic effects was the most appropriate model according to standard error of prediction. Direct heritabilities for body weight at birth and for 3, 6, 9, and 12 months of age were 0.23±0.02, 0.31±0.03, 0.36±0.04, 0.37±0.03 and 0.39±0.03, respectively. In current study the effect of maternal permanent environment on all traits was low and also negative correlation was observed between maternal and direct additive genetic effects. Although estimated heritability of maternal effects for body weight was lower in older ages, but probably using the maternal effects in the statistical model could cause in more accurate estimation of genetic parameters for growth traits in all ages.