Performance of steers given a molasses based diet and various protein and energy supplements. (Abstract)

Abstract

1OA PERFORMANCE OF STEERS GIVEN A MOLASSES BASED DIET AND VARIOUS PROTEIN AND ENERGY SUPPLEMENTS T.J. KEMPTON* Liquid molasses, supplemented with roughage and a source'of non protein nitrogen and bypass protein has been widely used as 'a productionration for lot feeding cattle (Preston & Willis, 1975). Addition of a sotirce of starch as maize grain to a molasses diet hati also increased voluntary food intake, growth rate and food conversion ratio in bulls (Preston & Willis, 1975). In this study, isonitrogenous supplements containing combinations of a bypass protein (soyabeanmeal)and starch (maize) were given to Hereford steers consuming a liquid molasses based diet. The steers received a molasses diet-which contained (w/w) 3% urea and 5% minerals. The steers also received 1.ka medium quality hav/hd/d and one of the following supplements (g/hd/d), a) 400 soyagean meal, b) 500 whole soya-' bean, c) 500 whole soyabean extruded at 150 , d) 480 soyabeans + 320 maize + 50 sodium bentonite, e) 480 soyabeans + 320 maize. + 50 sodium bentonite extruded at 150�. The experiment was conducted over an 80 day feeding period. The results were: Extrusion of the maize/soyabean/bentonite mixture supported maximum growth rate (1.1 kg/d) in relation to all other supplements (mean 0.56 kg/d). Since the quantity of protein and energy provided in both the unextruded and extruded maize + soyabean supplements was similar, the observed growth responses indicated a change in the balance of nutrients available for absorption by the animal, which was attributable to the effects of extrusion. Extrusion could have increased the supply of fermentable substrate in the.rumen and increased the efficiency of microbial protein synthesis, or it could have reduced the degradability of the protein and energy in the supplements and increasedthe flow of protein and energy to the intestines. PRESTON, T-R; and WILLIS, M-B. (1975). p. 334-336. Pergamon.Press. * 'Intensive Beef Production' Department of Biochemistry and Nutrition, University of New England, Armidale, NSW 2351