Abstract

Two experiments investigated the post-weaning nutritional requirements and subsequent growth rates of lambs born in May and June. The objective was to produce heavyweight lamb carcasses during the period of otherwise difficult supply (November to January). Experiment 1 examined the feed intake, growth rate and carcass composition of ram and ewe lambs born in late May (weaned late July) offered three pasture allowances. Pasture dry matter allowances of 6%, 12% and 22% of liveweight/head/day resulted in average growth rates of 68, 1109 and 148 g/d, respectively in weaned lambs over the period from July to January. Experiment 2 investigated growth rates of June born lambs fed pelleted supplements (420 g DM/head/day) at pasture. Weaned ram lambs were offered either high protein, medium protein or no supplements at two pasture allowances (12% and 22% of live weight/head/day) for 12 weeks between September and December. At the low pasture allowance the high protein supplement gave a 13% improvement in growth rate (P<0.05) over the medium protein supplement. For the final six weeks of the experiment, half of the high pasture allowance group was offered a white clover dominant pasture. Over this latter period the "clover" group had significantly higher growth rates (233 g/d) than lambs offered either high protein (204 g/d) or medium protein (184 g/d) or no supplements (161 g/d) at high pasture allowances. Carcass weights at slaughter (11th December) were 19.6, 18.6, 18.2 and 16.5 kg, respectively, for these four groups. High protein supplements at pasture increased lamb growth rates, particularly at a low pasture allowance. This would be useful during times of poor or unseasonal pasture production to ensure supply contracts are met, particularly for early, heavyweight lambs.

CA, Morris, RL Baker, and JC Hunter

Proceedings of the New Zealand Society of Animal Production, Volume 49, , 203-208, 1989