Abstract
Genetic parameters were estimated for birth weight and weaning weight from three year (1991-1993) data totalling 1100 records of 25 rams to 205 ewes of Indigenous Sabi flock maintained at Grasslands Research Station in Zimbabwe. AIREML procedures were used fitting an Animal Model. The statistical model included the fixed effects of year of lambing, sex of lamb, birth type and the random effect of ewe. Weight of ewe when first joined with ram was included as a covariate. Direct heritability estimates of 0.27 and 0.38, and maternal heritability estimates of 0.24 and 0.09, were obtained for birth weight and weaning weight, respectively. The total heritability estimates were 0.69 and 0.77 for birth weight and weaning weight, respectively. Direct-maternal genetic correlations were high and positive. The corresponding genetic covariance estimates between direct and maternal effects were positive and low, 0.25 and 0.18 for birth weight and weaning weight, respectively. Responses to selection were 0.8 kg and 0.14 kg for birth weight and weaning weight, respectively. The estimated expected correlated response to selection for birth weight by directly selecting for weaning weight was 0.26. Direct heritabilities were moderate; as a result selection for any of these traits should be successful. Maternal heritabilities were low for weaning weight and should have less effect on selection response. Indirect selection can give lower response than direct selection. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1690-1694)
Highlights
The Sabi sheep is the most common indigenous breed in Zimbabwe
Maternal heritabilities were low for weaning weight and should have less effect on selection response
Unlike for exotic sheep breeds, no estimates of both covariances components and genetic parameters for weight traits in indigenous Sabi sheep have been estimated to allow the development of sensible breeding programmes.The records of indigenous Sabi flock at Grasslands Research Station, Marondera, Zimbabwe small provided an opportunity to estimate the genetic parameters for birth weight and weaning weight
Summary
The Sabi sheep is the most common indigenous breed in Zimbabwe. It has similar features to Red Maasai and Tswana sheep of Eastern and Southern Africa (Mason and Maule, 1960). The resistance of their hairy coat to penetration by awned seeds allows the breed to enjoy wide distribution in the country. Unlike for exotic sheep breeds, no estimates of both covariances components and genetic parameters for weight traits in indigenous Sabi sheep have been estimated to allow the development of sensible breeding programmes.The records of indigenous Sabi flock at Grasslands Research Station, Marondera, Zimbabwe small provided an opportunity to estimate the genetic parameters for birth weight and weaning weight. (c) to predict responses to direct selection for birth weight and weaning weight
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