日粮瘤胃能氮平衡对奶牛生产性能和牛奶中尿素氮的影响

本研究以12头泌乳中期荷斯坦牛为研究对象，采用随机区组设计分为3组，在干物质进食量相似的条件下，增加瘤胃快速可发酵能量，用玉米粉颗粒替代甜菜渣颗粒，三个处理分别替换0kg、0．4kg和0．8kg，试验期61d。结果表明，日粮处理对奶牛的产奶量和乳成分没有明显影响，玉米粉颗粒替代甜菜渣颗粒饲喂奶牛后可显著降低牛奶中尿素氮（MUN）浓度，评价目粮的瘤胃能氮平衡表明为正平衡，有明显低水平的MUN。试验证明，可以用日粮瘤胃能氮平衡判断饲喂日粮对奶牛MUN的影响。

Effect of Dietary Rumen Energy and Nitrogen Balance on Milk Production and Milk Urea Nitrogen in Lactating Dairy Cows

The objectives of this study were to assess the relationship between dietary rumen energy and nitrogen balance （RENB） and milk urea nitrogen concentration （MUN, mg/dL）. Twelve mid-lactation Holstein cows were divided into 3 treatment groups and fed different diets containing different amounts of rumen fermentable organic matter. The experimental period was 61 days in length. In a similar dry matter intake, the milk production and milk composition were not affected by the RENB in the diet. Concentrations of MUN were affected by dietary RENB in the present study, there was a significantly lower MUN of cows fed the diet with a positive RENB, the RENB can be judged the MUN status effecting by diets.