Direct Maternal Genetic Effects and Birth Weight Trends of Indigenous Tuli Cattle of Zimbabwe

Abstract

The birth weight records of 3137 indigenous Tuli calves from Matopos Research Station in Zimbabwe, collected during 1988 - 1997 were analyzed to estimate the variance components and heritability of birth weight using the ASREML approach. A single trait animal model was fitted, allowing for genetic maternal effects and genetic covariance between direct and maternal effects. Estimates of heritability for direct genetic effects (h²_A), maternal genetic effects (h²_M) and the genetic covariance between direct and maternal effects as proportions of the total variance (c_AM) of birth 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 that selection should be directed at both components, considering the maternal heritability estimate, which was moderate. The environmental parameter records of the study area suggest that birth weight was not depressed by the tropical semi arid environmental conditions.