Estimation of Covariance Components and Genetic Parameters for Weaning Weight in Matebele Goat, Sabi, Dorper and Mutton Merino Sheep

Covariance components and genetic parameters were estimated from pedigree records of weaning weight (WWT) of indigenous Matebele goat (2110) from Matopos Research Station, Bulawayo, and, indigenous Sabi sheep (2342), Dorper sheep (1933) and Mutton Merino sheep (1548) from Grasslands Research Station, Marondera in Zimbabwe. Covariance components were estimated using the AIREML in animal model that included fixed effects of sex, year of birth, birth type and age of dam. Random effects were direct and maternal genetic of animal and dam with genetic covariance maternal permanent environmental, and random residual. Estimates of direct heritability were 0.36, 0.38, 0.48 and 0.28 for indigenous Matebele goat, indigenous Sabi sheep, Dorper sheep and Mutton Merino sheep, respectively. Estimates of direct heritability were 0.11, 0.09, 0.01 and 0.44 for indigenous Matebele goat, indigenous Sabi sheep, Dorper sheep and Mutton Merino sheep, respectively. Maternal heritability was higher than direct heritability for weaning weight in Dorper sheep. An estimate of permanent environmental variance as a proportion of phenotypic variance was negligible in goat and sheep breeds. When fitted in model estimates of genetic correlation between direct and maternal effects were observed positive and negative for weaning weight. There is high genetic variability in indigenous goat and indigenous sheep which can be exploited to improve weaning weight by mass selection.