Estimation of variance components and genetic parameters for some of reproduction traits in Mehraban sheep, using univariate animal models

This study was conducted to estimate genetic parameters of reproduction traits in Mehraban sheep. The data were collected from Mehraban sheep flocks of Hamedan province، during 1994 – 2008. Variance components of the studied traits were estimated using univariate animal models with derivative free approach of restricted maximum likelihood. Heritabilities of age at the first lambing، litter size، number of lambs born per year and number of total lambs born per ewe were estimated as 0. 15، 0. 06، 0. 04 and 0. 01، respectively. Estimates of heritability for litter average birth weight، litter average weaning weight، total litter birth weight، total lambs birth weight per year، total lambs birth weight per ewe، total litter weaning weight، total lambs weaning weight per year and total lambs weaning weight per ewe were 0. 04، 0. 17، 0. 08، 0. 03، 0. 09، 0. 11، 0. 09 and 0. 23 respectively. Estimates of the variance due to permanent environmental effects were negligible for the studied traits; therefore the estimates of heritability and repeatability for each trait were approximately equal. It was concluded that consideration of litter average weaning weight and the age at the first lambing، in the selection programs، is probably an effective method for genetic improvement of reproductive efficiency in Mehraban sheep.