Abstract:
FURTHER STUDIES OF THE EFFECTS OF DEFAUNATING THE RUMEN ON THE PRODUCTIVITY OF LAMBS S. BIRD* and R.A. LENG* Previous short-term studies of defaunated ruminants fed low protein diets demonstrated that productivity could be increased as a result of defaunating the rumen (Bird and Leng 1978; Bird et al. 1979). The -w increased productivity was attributed to an increased availability of microbial protein from the rumen, which has been shown to increase in duodenal digesta collected from defaunated sheep (Lindsay and Hogan 1972). Defaunation of the rumen is frequently associated with a lowering of rumen ammonia concentration, and in a recent study .in which lambs were fed a high energy/low protein diet (supplemented with 3% urea), the ammonia concentration in the rumen of defaunated lambs was only 35 mg/l (Burggraaf 1980). At this concentration, rumen ammonia may be Emiting microbial growth (Satter and Slyter 1974). This experiment was undertaken to examine the long-term effect ,of defaunation and an increased level of urea supplementation on the productivity of',lambs. Four groups of ten cross-bred lambs (15 kg) were fed a diet of oaten chaff and sugar (50:50) supplemented with 4% fishmeal and adequate vitamins and minerals and either 3 or 5 per cent urea. Following an equilibration period during which all lambs were defaunated, two groups of animals were refaunated and feed intake, weight change and wool growth were monitored over a 15 week period, and the results are given in Table 1. TABLE 1 The effects of defaunating the rumen onfeed intake/growth and feed conversion efficiency of lambs fed ad lib or basal diet of oaten chaff/sugar (50:50) + 4%.fishmzl + vitamins and minerals Defaunating the rumen stimulated wool growth by 33% ,and significantly improved the feed conversion ratio. The level of urea supplementation had no effect on the production parameters measured. BIRD, S.H. and LENG,'.R..A. (1978) Br. 'J. Nutr. 40: 163: BIRD, S.H., HILL, M.K. and LENG, R.A. (1979) BrTJ. Nutr. 42: 81. BURGGRAAF, W. (1980) Masters Thesis. University of New EngGnd, Armidale. ,LINDSAY, J.R. and HOGAN, J.A. (1972) Au,st. J, Agric. Res. 23: 321. SATTER, L.D. and SLYTER, L.L. (1974) Br. J. Nutr. 32: 199.'Department of Biochemistry and Nutrition, University of New Engl.and, 2351; * Armidale, N.S.Wc
