The value of supplementary feeding to pre-weaned and weaned lambs grazing Italian ryegrass

Abstract

The variation in, and often the disappointingly poor weight gains and the inability of lambs to achieve desirable carcass grades on ryegrass pastures have long been a concern to researchers, extension officers, advisors and farmers. The objectives of this study were to investigate whether concentrate supplementation to lambs on Italian ryegrass (Lolium multiflorum cv Midmar) pastures would improve the performance of lambs, and what the optimum level of supplementation is to lambs on the pasture. The investigation extended over the pre- and post-weaning growth phases of lambs and was conducted during two consecutive seasons at the Cedara Research Station in the KwaZulu-Natal Mistbelt. The pre-weaning stocking rate applied, was 20 South African Mutton Merino ewes with lambs/ha and the following treatments were applied: Control: continuous grazing - no creep feed; forward creep grazing by the lambs in a rotational grazing system where the lambs were allowed to graze paddocks allocated to the ewes, plus the next paddock in their series of grazing paddocks; 100 g creep feed/lamb/day; 250 g creep feed/lamb/day and creep feed ad libitum. The post-weaning stocking rate applied, was 50 lambs/ha and treatments were: Control - no supplement; 250 g of supplement/lamb/day (only the second season); 500 g of supplement/lamb/day and supplement ad libitum. From 42 days of age to weaning, supplementation significantly improved the live weight gain of suckling lambs. Creep feed intake varied between 300 and 350 g/lamb/day. The average daily gain of the weaned lambs improved significantly with supplementation. No significant advantage in terms of growth was gained by supplementing the weaned lambs at levels of higher than 500 g/day. South African Journal of Animal Science Vol.32(1) 2002: 30-37