Genetic analysis of growth traits in Muzaffarnagari sheep

Data on 4112 Muzaffarnagari sheep, maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, and recorded between 1976 and 1999, were analysed to study the growth-related traits and their genetic control. The average weights at birth, and at 12 months of age were 3.1 +/- 0.2 and 28.0 +/- 0.6 kg, respectively. The pre- and post-weaning average daily weight gains were 127.8 +/- 3.3 g and 49.4 +/- 1.6 g. and the associated growth efficiencies were 3.59 +/- 0.08 and 0.95 +/- 0.03. Significant differences associated with the year of lambing were observed in body weight, weight gain and efficiency in weight gain at different stages of growth. The lambs born in the dam's second parity were generally of heavier weight and higher daily weight gain than those born in other parities. Males were heavier and had a higher weight gain than females at almost all stages of growth and the differences tended to increase with age. Single-born lambs had a distinct advantage over those born in multiple births at all stages of growth. The heritabilities of all body weights, weight gains and efficiency in weight gains at different stages of growth were moderate (0.18-0.26), except for birth weight, which was of low heritability (0.068 +/- 0.01). The phenotypic and genetic correlations among the different body weights were positive and high, except for birth weight. The genetic correlation of the pre- and post-weaning average daily weight gains with body weights were high and positive.