Management of highly fecund ewe types and their lambs for 8-monthly lambing, 2. Effect of weaning age and sex on lamb growth and carcass traits
1992
Fogarty, N.M. | Hall, D.G. | Atkinson, W.R. (New South Wales Agriculture, Cowra (Australia). Agricultural Research Inst.)
The effect of weaning at ages ranging from 6 to 13 weeks on growth of lambs from Booroola Merino x Poll Dorset (BD), Trangie Fertility Merino x Poll Dorset (TD), and Border Leicester x Merino (BLM) ewes was examined in an 8-monthly lambing system. In the first year, there was a significant difference between growth rates to 3 months of age of lambs weaned at 12, 9, and 6 weeks. In the second year, lambs were weaned at weekly intervals from 6 to 13 weeks of age, and growth rates were higher because of better seasonal conditions. Using regression coefficients, lambs weaned at 12 and 9 weeks were estimated to have higher growth rates by 17 and 8 percent, respectively, than lambs weaned at 6 weeks. Weaning age had no effect on any carcass trait. Carcass weight accounted for most variation in carcass traits, and its inclusion in the model removed the effect of type of rearing. There was a significant crossbred type x carcass weight interaction for fat depth at the C site, due to progeny of BLM ewes being fatter than the other crossbred types at heavier carcass weights. There was no advantage from early weaning in management for an 8-monthly lamb production system because lamb growth and survival were depressed
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