Estimation of (co)variance component and genetic parameters for pre-weaning growth traits in shallsheep

Body weight traits prior to weaning are of special importance in sheep breeding programs.

In this study genetic parameters for pre-weaning growth traits in Shall sheep were estimated using data on birth weight (BW), weaning weight (WW) and average daily gain (ADG) from birth to weaning, collected during 1994 to 2009 in Qazvin province. The data belonged to four herds and included 1,992 records for BW, 1,584 records for WW and 1,568 records for ADG.

Six different models were used to estimate the genetic parameters. The most appropriate model was determined for each trait using likelihood ratio test.

The estimated direct heritability for BW, WW and ADG were 0.34, 0.48 and 0.21, respectively. Genetic correlations between traits were positive and medium to high. The phenotypic correlations were lower than the corresponding genetic correlations.

Due to high heritabilities estimated of birth and weaning weights and also high genetic correlation between these traits, direct selection for genetic improvement of these traits will be effective.