Direct and maternal effects for body measurements at birth and weaning in Muzaffarnagari sheep of India

Estimates of co(variance) components were obtained for body measurements at birth and weaning in Muzaffarnagari sheep maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 27 years (1978 through 2004). Records of 5821 lambs descended from 176 rams and 1698 ewes were used in the study. Analyses were carried out by REML fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits. The best model was chosen after testing the improvement of the log-likelihood values. Direct heritability estimates were inflated substantially for all traits when maternal effects were ignored. The direct heritability estimates for body length, height at withers and heart girth of lambs at birth were 0.14, 0.14 and 0.07, respectively. The corresponding maternal heritability estimates for these traits at birth were 0.13, 0.15 and 0.13, respectively. Moderate estimates of the direct heritability (h2) and the fraction of variance due to maternal permanent environmental effects (c2) for body length (h2 = 0.12, c2 = 0.08), height at withers (h2 = 0.16, c2 = 0.08) and heart girth (h2 = 0.15, c2 = 0.09) was observed at weaning. Results suggest that maternal additive effects were only important at birth for these traits but permanent environmental maternal effect had some influence on body measurements at weaning. These results indicate that modest rates of genetic progress appear possible for body measurements at birth and weaning.