Estimation of genetic parameters for growth traits and genetic and phenotypic trends of reproductive traits in the nomadic Lori sheep flocks

(Co) variance components and genetic parameters for growth traits including birth weight (BW), weaning weight (WW) and six-month weight (6MW) as well as parameters, genetic and phenotypic trends of reproductive traits including total weight of lambs weaned per the ewe (TWLW) and the number of lambs born at birth per ewe (NLBE) in Lori sheep were estimated using the Bayesian method. The data included 7363 records for BW, 7054 records for WW, 6765 records for 6MW, 1012 records for TWLW and 1048 records for NLBE. The data were collected by the Agricultural Organization of Lorestan Province between the 2001 to 2010 years (for growth traits) and 2003 to 2010 years (for reproductive traits). The estimates of direct heritability for lamb body weights were 0.36 at birth, 0.11 at weaning and 0.05 at six months of age. The genetic and phenotypic trends reproductive traits were calculated based on regression of the mean of breeding value on birth year and mean of phenotypic value on birth year, respectively. Heritability, genetic and phenotypic trends for TWLW trait were 0.05, 5.4±1.16 and 255±0.45 grams per year, respectively. Heritability, genetic and phenotypic trends of NLBE trait were 0.09, 0.002±0.02 and 0.125±0.07, respectively. Genetic improvement of TWLW and NLBE traits at considered period were 31.64 grams and 0.008 of Lamb. The estimate of heritability at birth was higher than other traits so selection based on this trait would increase the genetic advances. Genetic and phenotypic trends for reproductive traits were not significant and the genetic trend was low.