Influence of weaning age, management, and slaughter age on export lamb carcass production and slipe wool weights

Abstract

Abstract A series of five experiments was conducted over a period of 4 years with lambs weaned at 4, 5, 6, 9, 12, 15, or 18 weeks of age. Management treatments included restricted milk intake, creep grazing, rotational grazing, and set stocking. Slaughter ages ranged from 12 to 30 weeks. Early weaning at 4, 5, or 6 weeks caused varying post-weaning growth checks, lasting from 1 to 4 weeks, the most severe following 4-week weaning in the absence of creep grazing. Subsequent growth rates were similar to those for later-weaned lambs. Weaning lambs at 9 weeks of age resulted in similar final live weights to those obtained by weaning at 12 or 15 weeks. The reductions in final slaughter weights caused by early weaning (up to 21%) were associated in some experiments with lower killing-out percentages and reduced carcass fat. In one experiment, where treatments were compared at a common carcass weight of 17.5 kg, 4-week weaning resulted in 2–5% lower levels of chemical carcass fat and up to 4% and 1% higher values for water and protein respectively than in later-weaned lambs. Creep grazing in association with early weaning tended to minimise the growth check. Restricted milk intake before weaning at 5 weeks of age caused a prolonged growth reduction followed by no compensatory growth. Set stocking resulted in heavier weights for both early- and late-weaned lambs. A liberal supply of milk and grass before early weaning and the lack of subsequent compensatory growth are discussed. Favourable reasons for early weaning include reduction of carcass fat and removal of competition by ewes under conditions of feed shortage. The practice can also be used in association with sheep dairy production, accelerated lambing, or progeny test programmes. It is recommended that the conventional lamb weaning age be reduced to about 9 weeks.