Study On Requirement Pattern Of Sulfur & Copper And Effects On Nutrient Metabolism In Beef Cattle

Crossbred (Limousin × Lu-xi) beef cattle, fitted with permanent cannulas in rumen, the proximal duodenum and dismal ileum, was used in the study. Metabolism of nutrients was investigated by the determination of the outflow and disappearance rates of nutrients in digestive tract, acetic acid and propionate yield, or synthesis of microbial protein in rumen in beef cattle fed diets with different levels of nitrogen, sulfur, molybdenum, or copper. The ideal copper source and the requirement pattern of sulfur and copper were established. The results showed that based on the solubility in vitro, plasma copper concentration, and bioavailability, tri-basic copper chloride and copper carbonate basic may be ideal copper sources for beef cattle, and the bioavailability of tri-basic copper chloride was greater (P < .05) than that of copper carbonate basic. The experiments were conducted in Latin square designs to access the effects of dietary NPN or sulfur on metabolism of nutrients in beef cattle. The results indicated that with supplement of sulfur to diets with same level of urea, the concentrations of NH3-N, plasma urea nitrogen, and the apparent digestibility of sulfur reduced (P < .05) but the disappearance rates of DM, ADF, and NDF in rumen and the apparent digestibilities of them in whole digestive tract, the yield of propionate, and the ratio of sulfur-containing amino acid increased (P < .05). Supplement of sulfur to diets with urea improved (P < .05) the availability and safety of NPN, digestibility of cellulose, synthesis of sulfur-containing amino acids. The experiments were performed to investigate the metabolism of nutrients in beef cattle fed diets with different levels of nitrogen , sulfur and copper. The results indicated that the degradation of NDF and ADF in rumen or small intestine, plasma copper concentration, activities of Cp or SOD increased (P < .05) but concentration of NH.3-N decreased (P < .05) with increasing dietary copper in beef cattle fed diets with the same nitrogen to sulfur ratio. Cattle supplemented with NPN or S had greater (P < .05) activities of Cp or SOD, plasma copper concentration. In the presence of high dietary S concentration, bioavailability of dietary copper declined. The following experiments showed that plasma copper concentration and activities of Cp or SOD reduced (P < .01) with increasing dietary molybdenum. Copper supplemented cattle had greater (P < .01) plasma copper concentration, activities of Cp or SOD, and disappearance rate of ADF in rumen. Supplement of 5 mg of Mo/kg diet decreased (P < .05) the bioavailability of copper. Copper supplementation increased (P < .05) the bioavailability of copper. It suggest that optimal requirements of S were .150%, .225%, .300% for cattle fed diets containing 0%, 1%, and 2% urea respectively; the optimal requirements of copper were 10, 10 and 25 mg/kg for cattle fed diets containing urea and sulfur 0% and .150%, 1% and .225% , 2% and .300% respectively; the optimal requirements of copper were 10 and 25 ing/kg for cattle fed diets Supplemented with 0 and 5 mg of Mo/kg diet.