برآورد مولفه هاي (كو) واريانس و پارامترهاي ژنتيكي صفات پشم توليدي و تعداد بره متولد شده در هر زايمان ميش هاي لري بختياري

Estimation of (co) variance componenets and genetic parameters of Clean fleece weight and litter size in Lori-Bakhtiari ewes

In this study 4136 records of ewe Clean fleece weight and 3135 records of litter size collected during the period 1990-2000 from a flock at Rearing and Breeding of Lori-Bakhtiari sheep Station in Shahre-Kurd were used to estimate (Co)varianee components and genetic parameters of ewe Clean fleece weight and litter size. (Co)Variance components and genetic parameters were estimated using Derivative Free Restricted Maximum Likelihood (DFRFML.) with univariate and hivariate animal models including fixed effects of year, ewe age and regression coefficient of ewe body weight, and random effects of additive genotype of ewe, permanent environment and residuals. Least-squares means (A.s.e.) of ewe Clean fleece weight and litter size were 1.9510.01 kg and 1.1610.006 head, respectively. Effects ofʹ year and ewe age on traits under study were highly significant (pK0.001). Estimation of variance components from univariate were the same as hivariate analysis. Estimation of genetic (co)varianee components were 0.10840.0! 1 and 0.01610.005 for ewe Clean fleece weight and litter size and -- 0.002+0.005 for genetic covariance between them. Estimation of genetic parameters for ewe Clean fleece weight and litter size were respectively 0.56+0.04 and 0.13+0.04 for heretability, 0.64 and 0.28 for repeatability and -- 0.04+0.04 for genetic correlation between two traits. The results of this study showed that the rate of response to selection for litter size will be slow, while selection for ewe Clean fleece weight resulting considerable progress for this trait without any negative effect on litter size.