本试验旨在研究饲粮瘤胃能氮释放同步化对泌乳奶牛瘤胃发酵、生产性能及氮平衡的影响。试验采用4×4的拉丁方试验设计，试验动物为4头安装永久性瘤胃瘘管的泌乳中期荷斯坦奶牛，试验处理为4种瘤胃能氮释放同步化指数（SI）不同的等能、等氮饲粮（饲粮Ⅰ，SI＝0.95；饲粮Ⅱ，SI＝0.90；饲粮Ⅲ，SI＝0.83；饲粮Ⅳ，SI＝0.77）。每期试验19 d，其中预试期14 d，采样期5 d，采样期的最后2 d测定氮平衡。试验结果表明：1）瘤胃液pH随饲粮SI值的升高而降低（P<0.05）；乙酸、丙酸、丁酸及总挥发性脂肪酸浓度，氨氮浓度，瘤胃液相体积、稀释速率以及菌体氮外流量各处理间差异不显著（P>0.05）。2）产奶量、乳蛋白及乳糖产量随着饲粮SI值的升高而增加（P<0.05）；乳脂、乳糖、乳蛋白、乳尿素氮含量等各处理间差异不显著（P>0.05）。3）随着饲粮SI值的升高，乳氮、粪氮排出量升高（P<0.05），尿氮排出量减少，但各处理间差异不显著（P>0.05）；SI值对饲粮氮表观消化率、饲粮氮泌乳转化效率无显著影响（P>0.05）。结果显示，提高饲粮能氮瘤胃释放同步化程度具有促进菌体蛋白合成，提高乳蛋白产量的效果。
This experiment was conducted to study the effect of synchronization of dietary energy and nitrogen release on rumen fermentation, performance and nitrogen balance in lactating Holstein cows. A 4×4 Latin square design was used in this study. Four Holstein cows in mid-lactation fitted with ruminal cannulas were fed with four isoenergetic and isonitrogenous diets varying in synchronization index (SI) (diet Ⅰ，SI＝0.95; diet Ⅱ，SI＝0.90; diet Ⅲ，SI＝0.83; diet Ⅳ，SI＝0.77). Different diets contained similar CP and energy levels. The results showed as follows: 1)Rumen pH was decreased as synchrony level of diets increased（P＜0.05）, while concentrations of acetate, propionate, butyrate, total-volatile fatty acid and NH3-N, as well as rumen liqusid volume, liquid dilution rate and microbial N outflow did not differ significantly among the four diets with different SI values (P＞0.05). 2) Milk yield, milk protein and lactose tended to be higher when synchrony level of the diets was higher (P＜0.05), while milk compositions including milk fat, lactose, protein, and urea N were similar for cows fed with different diets(P＞0.05). 3)Milk N and fecal N loss were increased when synchrony level of the diets increased (P<0.05), while no significant difference was detected on urinary N, although it decreased as synchrony level of the diet increased(P＞0.05); Synchrony of diet also had no effect on apparent digestibility of nitrogen and efficiency of N intake used for milk N (P＞0.05). The results indicate that a greater degree of synchronization of dietary energy and nitrogen release has positive effect on microbial protein synthesis and milk protein production for dairy cows.［Chinese Journal of Animal Nutrition, 2011, 23（9）：1505-1512］
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