(Co)variance components, genetic parameters and trends for body weight traits in Muzaffarnagari sheep of India
Author(s): Ezhil Vadhana P, Ran Vir Singh, Gopal Dass and Anuj Chauhan
Abstract: The aim of present investigation was to estimate variance and covariance components, genetic parameters and genetic, phenotypic and environmental trends for body weight traits at different ages of Muzaffarnagari sheep for a period of 27 years (1991-2017). Phenotypic data was collected from Central Institute for Research on Goats, Makhdoom. The traits analyzed under present study were birth weight (BWT), weaning weight (WWT), 6 months weight (6WT), 9 months weight (9WT) and 12 months weight (12WT). Sex, season, year of lambing, parity and type of birth were included as fixed effects for mixed model analysis. Six animal models with different combinations of direct and maternal genetic effects were fitted by restricted maximum likelihood method using Wombat software. Bayesian information criterion was utilized for determining best model for all traits. Model 3 was obtained as the best model for all traits. Direct heritability estimates of BWT, WWT, 6WT, 9WT and 12WT are 0.29, 0.37, 0.47, 0.34 and 0.41 respectively and their respective maternal heritabilities were 0.31, 0.12, 0.19, 0.13 and 0.13. Negative covariance was observed between direct and maternal effects for all traits. The genetic and phenotypic correlation among the traits ranged from 0.23 (BWT-12WT) to 0.91 (9WT-12WT); 0.28 (BWT-9WT) to 0.84 (6WT-9WT and 9WT-12WT) respectively. Overall genetic and phenotypic and trends for all the traits were in desired direction. Negative estimates were observed for environmental trends. Desired genetic improvement obtained through selection is hampered by environmental interaction. Importance of maternal effect in influencing the traits was found in the investigation.
