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］
LI Peng,LIN Xueyan,SU Pengcheng,LIU Guimei,AI Jintao,WANG Zhonghua
. Synchronization of Dietary Energy and Nitrogen Release on Rumen Fermentation, Performance and Nitrogen Balance in Lactating Holstein Cows[J]. Chinese Journal of Animal Nutrition, 2011
, 23(09)
: 1505
-1512
.
DOI: 10.3969/j.issn.1006-267x.2011.09.008
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