日粮不同CP及RUP水平对奶牛瘤胃发酵的影响

试验旨在研究不同水平的粗蛋白（CP）及瘤胃非降解蛋白（RUP）的日粮对奶牛瘤胃代谢的影响。试验选择18头健康、体重相近的荷斯坦奶牛作为试验动物,随机分为6组,每组3头。采用2×3因子完全随机试验设计,其中CP设7.5%（低）、9.0%（中）、10.5%（高）3个水平,RUP设45%CP（低）、55%CP（高）2个水平,共6个处理组,饲喂相同基础日粮,精粗比为3∶7,预饲期10d,饲喂后2、4、8、12、24h从食道采集瘤胃液2d,测定瘤胃液pH值,NH3-N、微生物蛋白质（BCP）、挥发性脂肪酸（VFA）含量。结果表明,日粮CP水平对瘤胃液NH3-N浓度的影响极显著（P〈0.01）,对BCP及VFA的含量影响较小,总体而言,9.0%CP水平组对奶牛的瘤胃发酵略好于其他两组;日粮中高RUP（55%CP）可以显著降低瘤胃pH值且有降低NH3-N浓度的趋势,同时,对瘤胃BCP及VFA的合成有一定的促进作用。该试验条件下,日粮中CP（9.0%）和RUP（55%CP）可在一定程度上改善瘤胃代谢。

Effects of Different Levels of Crude Protein （CP） and Ruminal Undegradable Protein （RUP） in Ration on Rumen Fermentation

This experiment was conducted to study the effects of different levels of crude protein（CP） and ruminal undegraded protein （RUP） in ration on the rumen fermentation. 18 Holstein dairy cows were selected to study the effects of different levels of CP and RUP on the rumen fermentation parameters. This experiment was a 2×3 factorial arrangement with total 6 dietary combinations, the first factor was CP level （7.5%,9.0% and 10.5%）, and the second factor was RUP level （45% CP and 55% CP）. The ratio of concentration to forage was 3∶7. Pre -trial period was 10 d. The ruminal fluid samples were collected at the time points of 2, 4, 8, 12, and 24 h for 2 d. The results showed as follows： The rumen NH3-N concentration was significantly affected by CP levels of diets, but it had little effect on BCP and VFA contents. The rumen fermentation parameters for 9.0% CP level were slightly better than that of other levels; The high levels of RUP（55% CP）could reduce the pH value and NH3-N content in the rumen, and increase the concentrations of BCP and VFA in the rumen. Under the present experimental conditions, the results indicated that the treatment（9.0% CP） and RUP （55%CP） could slightly improve rumen fermentation.