Estimates of (co)variance components due to direct and maternal effects for lamb growth traits in Bharat Merino sheep

Estimates of (co)variance components were obtained for lamb growth traits in Bharat Merino sheep over a period of 17 years (1990–2006). Records of 2 630 lambs from 214 sires and 949 dams were used for this analysis. Data were analyzed by restricted maximum likelihood (REML), fitting an animal model ignoring or including maternal genetic and maternal permanent environment effect. Six different animal models were fitted for all traits. Overall additive genetic variability was very low in the flock for all the traits (h2 for birth, 3 and 6 month weight, ADG1 and ADG2 obtained from the best model were 0.06±0.02, 0.01±0.02, 0.01±0.01, 0.04±0.02 and 0.00, respectively). Maternal effects declined with the advancement of age. Partitioning of maternal effect into genetic and permanent environmental components was difficult. Correlation between direct and maternal genetic effect was high and negative. Complex models explained variation more efficiently than the simple models.