BAYESIAN ESTIMATION OF GENETIC PARAMETERS OF GROWTH TRAITS IN ZANDI SHEEP

This study was conducted at Ramin agricultural and natural resources university inKhuzestan of Iran in 2012 to 2013. In order to estimate the (co) variance components andgenetic parameters of growth traits in Zandi sheep, It was used a total of 6188 records of birthweight (BW), 5170 records of weaning weight(WW), 2994 records of 6 month weight(6MW), 2283 records of 9 month weight(9 MW) respectively which collected in the Khajiranimal breeding station from Tehran city during 1994-2010. The SAS statistical software wasused to determine the environmental factors that affect these traits and MTGSAM softwarewas used to determine genetic parameters of growth traits under Bayesian method.Environmental factors include year of birth, lamb sex, type of birth and age of dam had asignificant difference on all traits. It is entered the age of animal in to the model as covariateduring the weigh. It is estimated the heritability and variance components of each trait withBayesian method under the uni-trait animal model. By including or ignoring maternal geneticeffector or common environmental effects due to dam to direct additive genetic effects ofanimal, six different model of analysis were fitted into each trait. To find the best model foreach trait, it was considered the minimum residual variance. Mean and standard deviation ofBW, WW,6MW and 9 MW were 4.24±0.72, 21.48±3.79, 30.98±4.7, 32.8±4.53 respectively.Results showed that for BW, model was included direct additive genetic effects, maternaladditive genetic effects and maternal permanent environmental effects without consideringthe covariance between them. For WW, model was included direct additive genetic effects,  maternal additive genetic effects with considering the covariance between them. For 6 MW,model was included direct additive genetic effects, maternal additive genetic effects andmaternal permanent environmental effects with considering the covariance between them.For 9 MW, model was included direct additive genetic effects, maternal additive geneticeffects and maternal permanent environmental effects without considering the covariancebetween them. The direct estimated heritability of BW,WW, 6MW with the best model were0.124, 0.169, 0.258 and 0.163 respectively.