Effects of garlic oil on in vitro fermentation by microorganisms from goat rumen under substrates with different ratios of forage to concentrate | 不同精粗比底物时添加大蒜油对体外瘤胃微生物发酵的影响

Chinese. 体外法研究了底物精粗比（m（干草）∶m（精料））分别为10∶0、7∶3、5∶5、3∶7时,向发酵液中添加大蒜油（0、30、300和3 000 mg.L-1）对瘤胃微生物厌氧发酵24 h的影响。结果显示：24 h产气量随着大蒜油浓度的增加而降低（P〈0.05）,每隔3 h产气量的动态变化显示大蒜油延缓发酵的进行。大蒜油降低总挥发性脂肪酸（VFA）浓度（P〈0.05）,但是30 mg.L-1和300 mg.L-1之间没有显著差异（P〉0.05）;30 mg.L-1和300 mg.L-1大蒜油降低乙酸比例和乙酸/丙酸（P〈0.05）,增加丙酸和丁酸比例（P〈0.05）。3 000 mg.L-1大蒜油增加pH值（P〈0.05）,而30 mg.L-1和300 mg.L-1时对pH值没有影响（P〉0.05）。氨态氮（NH3-N）和菌体粗蛋白浓度从大到小分别依次是对照组、300 mg.L-1、30 mg.L-1、3 000 mg.L-1和30 mg.L-1、对照组、3 000 mg.L-1、300 mg.L-1。相对于其他发酵底物,在高精料时,30 mg.L-1和300 mg.L-1大蒜油的24 h产气量和总VFA浓度的降低较小,而NH3-N浓度、乙酸比例和乙酸/丙酸的降低以及丙酸比例的增加比较明显。结论：大蒜油抑制体外发酵存在剂量依赖效应,具有延缓发酵进程的特点,高精料时中等水平大蒜油对发酵的抑制作用较小,对发酵的优化作用更明显。

English. Different levels of garlic oil（0,30,300 and 3 000 mg・ L-1 of culture fluid） were incubated for 24 h in diluted ruminal fluid with substrates with different ratios of forage to concentrate（ 10：0,7：3,5：5 and 3：7 ） to investigate their effects on tureen microbial fermentation. Results showed that the 24 h gas production was reduced（ P〈0.05 ）with the increasing level of garlic oil. The dynamic changes of gas production per 3 hours showed that garlic oil delayed the process of fermentation. Compared with the control, garlic oil reduced total volatile fatty acids（VFA） concentration（ P〈0.05 ）, whereas there were no significant differences（ P〉0.05 ）between 30 and 300 mg・ L-1. The levels of 30 and 300 mg・L-1 reduced the proportion of acetate and ratio of acetate to propionate（ P〈0. 05 ） , and increased the proportions of propionate and butyrate （ P 〈 0.05 ）. Compared with the control, the high level of garlic oil （ 3 000 mg.L-1） increased pH （P〈0. 05 ）, while the levels of 30 and 300 mg. L-1 had no significant effects on pH （P〉 0.05 ）. The concentrations of ammonia （ NH3-N ） and microbial crude protein were reduced with the following order control, 300 mg. L-1 , 30 mg・L-1 ,3 000 mg.L-1 ,and 30 mg・L-1 ,control,3 000 mg・L-1 ,300 mg・L-1 ,respectively. Compared with the other substrates,garlic oil（ 30 and 300 mg・L-1 ）had minor reduction in 24 h gas production and total VFA concentration under high concentrate substrates, whereas it had more evident effects on reducing NH3-N concentration, acetate proportion and ratio of acetate to propionate, as well as increasing propionate proportion. In conclusion, garlic oil inhibited in vitro ruminal fermentation in a dose-dependent manner accompanied by delaying the process of fermentation. The moderate levels of garlic oil had minor depression and more optimization on rumen microbial fermentation under high concentrate substrates.