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

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。

Effects of garlic oil on in vitro fermentation by microorganisms from goat rumen under substrates with different ratios of forage to concentrate

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 rumen 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.