The aim of this study was to investigate the mechanism of sodium nitrate (NaNO3) and 2?bromoeth?anesulphonate ( BES) on methane inhibition from the biochemical aspect of ruminal hydrogen metabolism. Ru?men fluid was collected from two adult Xiangdong black goats with permanent rumen fistulas. The study con?tained control group, NaNO3 groups ( supplemental level was 0.10, 0.20 and 0.40 mg/mL, respectively) and BES groups (supplemental level was 0.63, 1.26 and 2.52 mg/mL, respectively). The 24 h in vitro ruminal incubation was performed to obtain gas production, production and contents of hydrogen and methane, and volatile fatty acids production and composition using automatic fermentation equipment. The results showed as follows: NaNO3 and BES supplementation significantly lowered methane production in comparison with control group ( P<0.05) , and increasing supplemental level of NaNO3 and BES linearly decreased methane production ( P<0.05) . The lower supplemental level of NaNO3(≤0.20 mg/mL) had no significant effects on gas produc?tion, initial fractional rate of degradation (FRD0), acetate and propionate production and the ratio of acetate to propionate (P>0.05), while the higher supplemental level of NaNO3(0.40 mg/mL) had significantly higher hydrogen production ( P<0.05) , and significantly lower gas production, methane production, FRD0 and total volatile fatty acids production in comparison with control group ( P<0.05) . BES had no significant effects on hydrogen production, FRD0 and total volatile fatty acids production in comparison with control group ( P>0.05), but had significantly higher hydrogen production and content (P<0.05), and decreased the ratio of ac?etate to propionate (P<0.05). BES could alter pattern of rumen fermentation through facilitating propionate production. In conclusion, NaNO3 reduces methane production through hydrogen sink and rumen microbial tox?icity, while BES reduced methane production through inhibiting the activity of methanogens, and had little effects on gas production and substrate degradation.%本试验从瘤胃氢代谢生物化学过程的角度出发,研究硝酸钠和2-溴乙烷磺酸钠( BES)对瘤胃甲烷生成的抑制机制. 选用2只装有永久性瘤胃瘘管的成年湘东黑山羊作为瘤胃液供体,设对照组、硝酸钠组(添加剂量分别为0.10、0.20和0.40 mg/mL)和BES组(添加剂量分别为0.63、1.26和2.52 mg/L) ,采用全自动体外模拟瘤胃发酵设备,进行24 h体外瘤胃发酵试验,测定产气量、氢气和甲烷的产量和含量、挥发性脂肪酸产量及组成. 结果表明:与对照组相比,添加硝酸钠和BES后,甲烷产量显著降低(P<0.05),并且随添加剂量增加,呈现线性下降的变化趋势( P<0.05). 低剂量硝酸钠(≤0.20 mg/mL)对产气量、起始底物降解速率、乙酸、丙酸产量和乙丙比无显著影响(P>0.05);高剂量硝酸钠(0.40 mg/mL)显著提高了氢气产量及含量,显著降低了产气量、甲烷产量及含量、起始底物降解速率和总挥发性脂肪酸产量( P<0.05);添加BES对产气量、起始底物降解速率和总挥发性脂肪酸产量没有显著影响(P>0.05),但显著增加了氢气产量及含量(P<0.05),显著降低了乙丙比(P<0.05),发酵类型向丙酸型转变. 由此可见,硝酸钠减少甲烷生成依靠其氢池和瘤胃微生物毒性作用,而BES减少甲烷生成依靠抑制甲烷产生,对气体生成和饲料的降解影响很小.
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