Estimation of genetic and phenotypic correlations among production and reproduction traits in Shal sheep

Document Type : Research Paper

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Abstract

The purpose of this study was to estimate genetic and phenotypic correlations between production, Body weight at birth (BWT), Weaning weight (WWT), 6 month weight (BWT6M) and yearling weight (BWT12M) and ewe reproduction traits including total number of lamb’s born (NLB/EL) and weaned (NLW/EL) and total weight of lambs born (TLBW/EJ) and weaned per ewes joined (TLWW/EJ) of Shal sheep born from 1998 to 2009 at Agricultural Jahad Organization. Data were related to 6221 lambs descending from 180 rams and 4060 ewes. Bivariate analysis for estimate the genetic covariance was conducted. Direct additive genetic correlations between body weights at different ages, were positive and moderate to high (ranged from 0.56 to 0.88) and phenotypic correlation between these traits were estimated positive, but with lower than respected genetic correlations. Direct additive genetic correlations between body weight at different ages and TLWW­/EJ were positive and high (ranged from 0.76 to 0.91) and phenotypic correlations between them were positive however they were less than genetic correlations. Direct additive genetic correlations between body weight at different ages with NLB/EL and NLW/EL were positive and moderate to high (ranged from 0.44 to 0.89) and phenotypic correlations between them were also positive but lower. The results of this study indicated that direct selection for body weight at early stage of life, can improve ewe composite reproduction traits.

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