Abstract:
Proc. Amt. Sot. Anim. Prod. ` 994 Vol. 20 I EFFECTS OF A 50-DAY PERIOD OF SLOW LIVEWEIGHT LOSS ON THE BODY COMPOSITION OF CROSSBRED WETHERS D.M. MURRA YA and OLGA SLEZACE K B ADcpt of Wool and Animal Science, University of N.S.W., Kensington. N.S.W. 2033 BSchool of Agriculture, University of Western Sydney, Hawkesbury, N.S.W. 2753 Merino wethers utilise body fat less rapidly than they deposit it over the liveweight range 23 to 33 kg (Aziz et al. 1.992). This study aimed to evaluate the changes in body composition of crossbred wethers (Border Leicester x Merino ewes and Dorset Horn rams) after a 5 kg decrease in liveweight over 50 days. To this end, 8 weaner sheep were fed ad libitum from 25 to 30 kg when 4 were killed and then the other 4 were fed to lose 5 kg at 100 g/day and killed. The common pelleted diet fed was composed of 80% lucerne chaff and 20% cereal grain (14.1% crude protein and 18.9 MJ GE/kg, both on a dry matter basis). The composition of the sheep was assessed by methods described by Slezacek (1976) and are shown in Table 1. Table 1. Mean component weight (kg) before and after weight loss (s.d.) The results obtained show that a liveweight loss of 5 kg had no apparent effect on body fatness. This null response, however, was associated with a significant weight reduction in other body components including some, so called, vital organs (lungs, liver, kidneys, pancreas and gut tissue). Thus sometimes body fat may not act as a readily available source of energy to prevent weight loss of such tissues during liveweight loss. AZIZ, N.N., MURRAY, D.M. and BALL, R-0. (1992)-J. Anim. Sci. ` 1819-28. 70: SLEZACEK, OLGA (1976). M.Sc. Thesis, University of New South Wales. 397
