Estimation of (CO) variance components for growth traits in Magra sheep

The objective of the study was to estimate the (co)variance components and genetic parameters for different growth traits of Magra flock maintained at the Arid Region Campus, ICAR-Central Sheep and Wool Research Institute, Bikaner, Rajasthan. The study comprised records of 2309 animals distributed over a period of 12 years (1999–2010). The estimation was done by restricted maximum likelihood procedures, fitting six animal models with various combinations of direct and maternal effects. The direct heritability estimates from the best model, as per likelihood ratio test for body weights at birth, 3, 6, 9 and 12 months of age and average daily gain from birth to 3, 3–6 and 6–12 months of age were 0.37±0.04, 0.25±0.04, 0.24±0.04, 0.36, 0.36±0.06, 0.21±0.04, 0.20±0.04 and 0.16±0.05, respectively. The genetic correlation between direct and maternal genetic effects was found to be moderate to large and negative for all the traits, indicating antagonistic pleiotropy, which must be considered while formulating breeding plans. Moderate to high heritability estimates indicate the presence of genetic variability in the flock that can be utilized for improvement of these traits through selection.