Estimation of (co) Variance Components for Growth Traits of Shall Sheep using Different Animal Models

The objective of this study was to investigate genetic and phenotypic parameters of body weight of shall lambs in different ages. Records of growth traits obtained from 6,692 lambs (progeny of 195 rams and 1,288 ewes) were used. The records of birth weight, BW (6,690 records), 3-month weight, W3 (6,654 records), 6- month weight, W6 (6,662 records), 9-month weight, W9 (6,599 records) and 12-month weight, W12 (6,528 records) collected between 1997 and 2013 in Shal Breeding Station in Ghazvin province were used. Genetic parameters were estimated applying restricted maximum likelihood method fitting an animal model using WOMBAT program. Test of significance for the fixed effects was carried out using SAS 9.2 software. The mean ± standard deviation of BW, W3, W6, W9 and W12 were 4.31±0.92, 20.90±3.46, 34.13±3.92, 47.42±4.21, and 60.46±4.28 kg, respectively. Direct heritability estimates were 0.13±0.02, 0.57±0.05, 0.52±0.05, 0.79±0.04 and 0.73±0.05 for BW, W3, W6, W9 and W12 respectively. The highest maternal heritability was estimated for W9 (0.32±0.02).