AND MATERNAL (CO)VARIANCE COMPONENTS AND HERITABILITY ESTIMATES FOR BODY-WEIGHT AT DIFFERENT AGES AND FLEECE TRAITS IN AFRINO SHEEP

Data, consisting of 4325 lamb records, the progeny of 146 sires and 94 6 darns, collected on the Carnarvon Afrino flock over the period 1975 to 1992, were used for this study. Variance components resulting from direct additive genetic effects, maternal additive genetic effects, ma ternal permanent environmental effects, as well as the relationship be tween direct and maternal effects for birth weight, monthly body weigh t from weaning at 4 months to 12 months of age, 18 month body weight, 16 month clean fleece weight and 16 month mean fibre diameter were est imated by REML procedures. By ignoring or including maternal genetic o r environmental effects, five different models of analysis were fitted in order to determine the most effective model for each trait. The di rect heritability estimate for body weight increased from birth (0.22/-0.04) up to 8 months of age (0.59+/-0.06), where it seemed to stabil ise. Maternal heritability estimates for body weight, on the other han d, increased from birth (0.09+/-0.04) to 5 months of age (0.17+/-0.02) , whereafter it decreased gradually. The maternal permanent environmen tal effect was significant only for birth weight (0.12+/-0.03). Direct heritability estimates of 0.62+/-0.04 and 0.73+/-0.03 were obtained f or clean fleece weight and mean fibre diameter, respectively. Maternal effects had no significant influence on clean fleece weight or mean f ibre diameter.