Effects of variation in age and birth weight on fleece traits at eighteen and thirty months

Abstract

Simple regression coefficients of fleece traits, measured at 18 and 30 months of age, on variations in age at sampling (as determined by the date of birth) and on birth weight were calculated for eight flocks in Western Victoria (4 Merino, 3 Corriedale, 1 Polwarth). The regression coefficients of fleece traits on age variation were generally small and not significant. The regression coefficients of fleece traits on birth weight generally showed an increase in greasy and clean fleece weight and per cent clean scoured yield, and a decrease in mean fibre diameter with increase in birth weight. Variation in age and birth weight contributed to the variation in clean wool weight at 18 months of age by 0.1-5.2 per cent, and 0.1-6.2 per cent respectively; at 30 months of age, the contributions were 0.1-2.3 per cent and 0.0-11.0 per cent respectively. Merino, Corriedale, and Polwarth lambs had mean days of birth (from day of first lamb birth) of 20.6, 22.3, and 14.4, and mean birth weights of 7.85, 8.01, and 9.68 lb respectively.