Abstract:
448 Proc. Aust. Soc. Anim. Prod. Vol. 17 WHOLE COTTONSEED IN A WHEAT-BASED MAINTENANCE RATION FOR WETHERS S.A. NEUTZE*, H.M. WARREN* and J.M. MORRISON* Fuzzy whole cottonseed (WCS) has been used as an energy and protein source for ruminants and contains approximately (g/kg DM) 34 N, 480 acid-detergent fibre and 230 crude fat. Cereal grains often become scarce during drought and WCS may be a cheap partial substitute, improving the protein content of the ration. The present experiment examined the effect of WCS on performance and health of wethers. 30 two year old Merino wethers were randomized into three groups of the average live weight (36.6 kg) and clean wool growth rate. Animals were same individually penned and offered maintenance rations (on an energy basis) with whole wheat grain to WCS ratios of 1OO:O (A), 75:25 (B) or SO:50 (C), and (g/d) 5 salt, 7 lime and 10 sodium bentonite. These rations were offered once daily for 138 days with free access to water. Midside wool patches and blood for haematology and serum enzymes (creatinine kinase and aspartate KK) aminotransferase (AAT-GOT)) were taken throughout the trial. A digestibility study was done using five sheep per group and three sheep per group were killed for postmortems and histopathology. a,b means with unlike superscripts differ significantly (P 0.05) N intakes were similar across treatments. Digestibility was markedly reduced by 50% WCS, presumably due to the 13% oil in the ration. Despite this, 25 and 50% WCS gained significantly more weight those animals given and produced, respectively, 27 and 36% more wool than those on 100% wheat. The high levels of oil may have depressed ruminal proteolytic activity, leading to an increase in undegraded dietary protein and hence amino acids reaching the duodenum. Sheep given WCS showed subclinical anaemia and renal haemosiderosis, possibly due to gossypol in the WCS (Menaul 1923). Serum levels of CK and AAT-GOT became elevated (P 0.01) on WCS relative to wheat by days 127 and 43 of the trial respectively, indicating tissue damage (Prasse 1986), possibly from gossypol or unsaturated fatty acids in cottonseed oil. Despite reduced digestibility and 25% WCS can be safely included in a particularly advantageous with regard adding more than 25% WCS or feeding for subclinical effects on health, at least wheat-based maintenance ration, and is to wool growth. Caution is advised in more than five months. MENAUL, P. (1923). J. Agric. Res. 26:233. PRASSE, K.W. (1986). Clinical Pathzogy, Proc. No. 93. p. 33. Post-graduate Committee in Veterinary Science. (University of Sydney). * Nutrition and Feeds Evaluation Unit, CVL, GLENFIELD, N.S.W. 2167