饲粮能氮瘤胃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

摘要

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 syn chrony 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 in creased 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.%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5d,采样期的最后2d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.