Estimation of genetic parameters for growth traits in Mehrabani sheep

This research was carried out to estimate genetic and phenotypic parameters for growth traits of Mehraban sheep. The data included the birth weight (BW، n=6645)، 3-month weight (3MW، n=3685)، 6- month weight (6MW، n= 2406) and 9-month weight (9MW، n=1684) records that were collected from 1994 to 2010 at Mehraban Sheep Breeding center under supervision of Agriculture-Jahad Organization of Hamedan. The pedigree file consisted of the information of animals from 1987 to 2010 years of birth. The effects of herd-year، season، sex، type birth and age of dam at lambing were fitted in the model as fixed effects. Due to the variation between ages at weighting of lambs this effect considered as a covariate in the model. The significant of fixed effects were determined using general linear model (GLM) procedure of SAS software. Bayesian analysis was carried out for traits، using the GIBBSS3F90 program. The most suitable model for each trait was determined based on deviance information criterion (DIC). The estimated direct heritabilites with most appropriate model were 0. 24، 0. 43، 0. 43 and 0. 23 for BW، 3MW، 6MW and 9MW traits، respectively. The estimated maternal heritabilites were 0. 04، 0. 43 and 0. 19 for BW، 3MW and 9MW، respectively. The results of this research show that a fair rate of genetic progress seems possible by selection for all traits، but negative genetic correlation was observed between direct and maternal genetic effects for all the traits، indicating antagonistic pleiotropy، which needs special care while formulating breeding plans.