【作者】 杨在宾；

【导师】 贾志海；

【作者基本信息】 中国农业大学 ， 动物营养与饲料科学， 2004， 博士

【摘要】 本研究以利木赞×鲁西黄牛杂交一代公牛为研究对象，应用永久性瘤胃瘘管、十二指肠近端瘘管、回肠末端瘘管和颈静脉插管技术，通过不同消化道营养物质流通量和消失率的测定，瘤胃乙酸、丙酸产量和微生物蛋白质合成的检测，氮、硫、铜平衡试验等，系统研究了不同氮、硫、钼、铜水平下肉牛营养物质代谢，并结合生物学利用率研究，选择出肉牛适宜的铜源以及不同NPN和钼水平下肉牛硫、铜的适宜供给量模型。 体外法溶解度(in vitro)、血铜浓度和生物学利用率研究结果表明：碱式碳酸铜和碱式氯化铜均可以作为肉牛铜源，碱式氯化铜的生物学利用率优于碱式碳酸铜(P＜0.05)。 根据三个日粮NPN水平(0％，1％和2％尿素)和三个硫水平(0.150％、0.225％和0.300％)，采用三期3×3拉丁方设计，研究了不同NPN利硫水平对肉牛营养物质代谢，结果表明：同一尿素日粮条件下，添加0.150～0.300％的无机硫可降低瘤胃氨氮浓度、硫的表观消化率和血浆尿素氮浓度(P＜0.05)；提高ADF、NDF在胃区的消失率和全消化道的表观消化率，提高氮、硫平衡和瘤胃液丙酸产量，增加不同消化道总氨基酸和含硫氨基酸的流通量，提高含硫氨基酸占总氨基酸的比例(P＜0.05)；在含尿素日粮中，提高日粮硫水平可提高NPN的利用率和使用的安全性，有利于纤维性物质的消化，促进含硫氨基酸的合成，改善肉牛氨基酸的平衡(P＜0.05)。 不同NPN、硫和铜水平下肉牛营养物质代谢研究结果表明：日粮NPN和硫水平一定时，增加铜水平，能提高胃区和小肠NDF和ADF的降解率、血铜浓度、血清铜蓝蛋白和SOD的活力(P＜0.05)，瘤胃氨氮浓度有下降趋势(P＜0.05)；在日粮铜水平一定时，提高NPN和硫水平，可使血清铜蓝蛋白和SOD的活力下降，血铜浓度降低(P＜0.05)，说明高硫对铜产生了拮抗，进而影响了血铜的浓度。但是，微生物蛋白质合成增加。 根据两个日粮钼水平(0.225％和5.225％)和三个铜水平(11.71，26.71和51.71mg／kg)，采用两期3×3拉丁方设计，研究了不同钼、铜水平下肉牛营养物质代谢，结果表明：提高日粮钼水平能显著降低肉牛血铜水平、血清铜蓝蛋白和SOD活性(P＜0.01)。同一钼水平下，提高日粮铜水平可提高肉牛血铜水平、血清铜蓝蛋白和SOD活性、ADF瘤胃消失率(P＜0.01)。5mg／kg日粮钼能降低铜的生物学利用率，提高日粮铜水平，能提高铜的生物学利用率(P＜0.05)。 通过肉牛瘤胃氨氮浓度、VFA产量、含硫氨基酸和微生物蛋白质合成、纤维物质降解、氮和硫平衡、血铜浓度、SOD和血清铜蓝蛋白活性测定等多种途径研究证明：肉牛饲喂0％、1％和2％尿素日粮时，硫的适宜供给量为0.150％、0.225％和0.300％日粮硫；日粮中尿素和硫水平分别为0％和0.150％、1％和0.225％、2％和0.300％时，肉牛铜的适宜供给量相应为：10mg／kg、10mg／kg和25mg／kg日粮铜；日粮中不添加钼和添加5mg／kg钼时，肉牛铜的适宜供给量为：10mg／kg和25mg／kg日粮铜。更多还原

【Abstract】 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.更多还原