Genetic Parameters Estimation and Trends for Birth Weight in Cattle

In this study data on birth weight (BWT) of local Tuli calves collected from 1988- 1997 at Matopos Research Station, located in Bulawayo, Zimbabwe were analyzed. A single trait animal model was fitted allowing for genetic maternal effects and a genetic covariance between direct and maternal effects. Estimates of heritability for direct genetic effects (h²A), maternal genetic effects (h²M), and the genetic covariance between direct and maternal effects as a proportion of the total variance (cAM) for weaning weight were, 0.25, 0.14, -0.06, respectively. Direct additive genetic variance was twice larger than maternal variance. The correlation between direct and maternal effects was negative implying selection be directed at both components considering the maternal heritability estimate which was moderate. The natures of environmental values suggest that birth weight was not depressed by the tropical harsh semi arid environmental conditions.