Variance components and heritabilities for body weight traits in Sangsari sheep, using univariate and multivariate animal models

The records of growth traits of 2778 lambs of Sangsari sheep flock from Damghan research station (Semnan Province, Iran), collected during 1986–1998, were analyzed to estimate the variance components and heritabilities of some growth and gain traits, using a Derivative Free, Restricted Maximum Likelihood (DFREML) approach.The single and/or multiple trait animal models were employed to perform the mentioned task. Different models of DFREML run for univariate analysis and log likelihood ratio for different models were compared to locate the most appropriate model for the analysis of each trait. With univariate analysis, direct heritability estimates for birth weight, weaning weight, 6 months weight, 9 months weight, yearling weight, average daily gain from birth to weaning, average daily gain from birth to 6 months of age and average daily gain from weaning to 6 months of age were 0.33 ± 0.05, 0.17 ± 0.05, 0.49 ± 0.07, 0.08 ± 0.05, 0.10 ± 0.05, 0.03 ± 0.02, 0.17 ± 0.60 and 0.05 ± 0.30, respectively. Maternal heritability estimates were 0.65 for birth weight, 0.08 for weaning weight, 0.01 for average daily gain from birth to weaning and 0.11 for 6 months weight. The results of pair-wise and multivariate (five traits) analyses for heritability estimates are also reported, which are not very different from those mentioned above. The results of this study showed that maternal heritability was higher for pre-weaning than for post-weaning traits.