Comparison of nitrate reduction, methane production and fermentation characteristics among ruminal microbial fractions | 瘤胃微生物不同区系的硝态氮还原、甲烷产生和发酵参数比较

Chinese. 【目的】以硝态氮为惟一氮源,评价体外培养瘤胃微生物不同区系还原硝酸盐的程度以及对甲烷产生和发酵参数的影响。【方法】采用Menke人工瘤胃产气法进行24h厌氧发酵,以硝酸钠、可溶性淀粉和微晶纤维素组成纯合日粮,用物理离心和化学抑制剂相结合的方法,将瘤胃液分成8种区系：全瘤胃液(WRF)、原虫(P)、细菌(B)、真菌(F)、原虫+细菌(P+B)、原虫+真菌(P+F)、细菌+真菌(B+F)和负对照(CTN),测定微生物硝酸盐降解率及发酵参数。【结果】P区系硝酸盐降解率显著高于B区系(P＜0.001),P+F及B+F区系硝酸盐降解率低;WRF产气量和硝酸盐降解率最高,P+B和P区系次之,这3个区系的甲烷(CH4)、总挥发酸(TVFA)含量和乙酸比例均高于其它区系(P＜0.001);硝酸盐的还原有利于微生物蛋白的合成,P+B区系的合成量最高。【结论】瘤胃原虫(P)和细菌(B)区系具有高还原硝酸盐(NO3-)和亚硝酸盐(NO2-)能力,原虫区系的硝态氮还原能力更强;真菌(F)区系培养于此发酵底物中,还原硝酸盐的能力很弱,几乎可以忽略。瘤胃原虫和细菌区系是硝态氮还原、产甲烷和微生物蛋白合成的主要区系。

English. 【Objective】 An in vitro study was conducted to evaluate the ability of nitrate reduction and its effect on ruminal methano genesis and fermentation characteristics of various microbial fractions. 【Method】 Using the Menke’s gas production method in vitro, pure substrates formulated with soluble starch, Avicel, and sodium nitrate were anaerobicly incubated for 24 hours. Physical centrifugation and chemicals selections were used to differentiate microbial fractions as follows: whole rumen fluid (WRF), protozoa (P), bacteria (B), fungi (F), protozoa plus bacteria (P+B), protozoa plus fungi (P+F), bacteria plus fungi (B+F), and negative control (CTN). 【Result】 The results showed that the degradation of nitrate by fraction P was higher than fraction B (P＜0.001), while fraction F had little contribution to nitrate reduction, even for its co-culture with fractions of P or B. The gas production and nitrate reduction were greatest in WRF, followed by fractions of P+B and P, and the three fractions had greater values in methane (CH4) proportion, total VFA (TVFA) concentration and acetate molar proportion (P＜0.001). Nitrate-N addition increased rumen microbial protein synthesis with the greatest synthesis occurring in P+B fraction. 【Conclusion】 Both ruminal fractions of P and B had the ability to reduce nitrate (NO3-) and nitrite (NO2-) with a greater ability in P fraction. F fraction had minor ability of nitrate reduction in this substrate. Ruminal protozoa and bacteria represented predominant populations responsible for nitrate reduction, methanogenesis, and microbial protein synthesis.