关键词: 硝态氮, 连续培养, 瘤胃发酵, 微生物合成效率

Abstract:

【Objective】 The study was conducted to evaluate the effect of dietary nitrate N addition level on the rumen fermentation and microbial efficiency. 【Method】 The experimental diets were formulated with six dietary nitrate N addition levels including 0, 6%, 12%, 18%, 24% and 30%, respectively. The fermentation in vitro was carried out in dual-flow continuous culture system lasting for 144 h. 【Result】 As dietary nitrate N addition level increased, ruminal pH and total VFA of fermenter contents were unchanged (P＞0.05), while the molar percentages of propionic acid (Q, P＜0.01) increased, and acetic acid (Q, P＜0.01) and ammonia concentration decreased (Q, P＜0.01). At the same time, there were quadratic increases (Q, P＜0.01) in the digestibility of DM, OM and CP. Microbial efficiency (MOEEF) increased quadratically (Q, P＜0.01) as dietary nitrate N addition level increased.【Conclusion】 Theses results indicated that dietary nitrate N could be used by ruminal microorganisms. As dietary nitrate N addition level increased, the ruminal fermentation parameters, digestibilities and MOEEF changed in varying degrees. Besides, ruminal MOEEF and fermentability were greater at the dietary nitrate N addition range of 12% to 18%.

Key words: nitrate N, dual-flow continuous culture, rumen fermentation, MOEEF