SUPPLEMENTATION OF HIGH FECUNDITY BORDER-LEICESTER X MERINO EWES WITHA HIGH-PROTEIN FEED - ITS EFFECT ON LAMB SURVIVAL

Two hundred and fifty Border Leicester x Merino ewes (40% heterozygous for the Booroola Fec B gene) were used in an experiment, replicated o ver 2 years, to examine the effects of cottonseed meal-based supplemen tation on lamb survival, birth, marking and weaning weight, as well as , liveweight and fleece characteristics of ewes. From 50 to 100 days o f pregnancy, half of the ewes were supplemented with 80 g/head.day. Th e supplemented group was then split according to litter size and, unti l 30 days after lambing, were offered pellets at 80, 160 and 220 g/hea d.day, respectively, for ewes bearing single, twin and triplet (or mor e) lambs. Over the 2 years, ewes averaged 2.11 lambs per parturition a nd supplementation significantly increased lamb survival to weaning (7 3 v. 58%) with no interaction with litter size. Although supplementati on had a positive effect on birth weight of all but twins, the effects of supplementation on survival were independent of birth weight effec ts. Significant effects of year, sire breed and litter size on lamb su rvival and birth weight were also noted. No effects of supplementation were apparent on lamb growth while ewe age, sire breed, sex and reari ng rank all significantly influenced growth rates. Ewe weights, fleece weights and staple strength were significantly influenced by year, ew e age and litter size but not by supplementation. These findings indic ate the benefits to lamb survival of providing a 'bypass' protein supp lement to high fecundity flocks even when ewes are grazing good qualit y pastures.