低聚木糖对奶牛瘤胃体外发酵、甲烷产量和微生物菌群的影响OA

This study was conducted to investigate the effects of xylooligosaccharides(XOS)on rumen fermentation,methane(CH4)production,and microbial populations in vitro.Rumen fluid was collected from three Holstein cows in mid-lactation.Using 2 g of total mixed ration(TMR)as the fermentation sub-strate,XOS were added at concentrations of 0％(control group),0.1％,0.2％,0.4％,and 0.8％.After 24 h of in vitro fermentation,gas production and CH4 production were measured.Fermentation fluid and substrate resi-dues were collected to determine volatile fatty acids(VFA)and in vitro dry matter digestibility(IVDMD).Real-time quantitative PCR was used to quantify microbial populations in the fermentation fluid from the control group and the 0.4％XOS group.The results showed that:(1)Compared with the control group,gas production in all experimental groups was significantly reduced(P＜0.05),and CH4 production in the 0.4％XOS group was signif-icantly decreased(P＜0.05).(2)The IVDMD in the 0.4％XOS group was significantly higher than that in the control,0.1％XOS,and 0.2％XOS groups(P＜0.05).There were no significant differences in acetate,propio-nate,and butyrate concentrations among all groups(P＞0.05).The acetate-to-propionate ratio in the 0.1％XOS and 0.4％XOS groups was significantly lower than that in the other three groups(P＜0.05),but no significant difference was observed between the 0.1％XOS and 0.4％XOS groups(P＞0.05).(3)Com-pared with the control group,the populations of total bacteria,protozoa,methanogens,and Ruminococcus flavefaciens in the 0.4％XOS group were significantly reduced(P＜0.05),while there were no signifi-cant differences in the populations of Fibrobacter succinogenes and Ruminococcus albus between the two groups(P＞0.05).(4)Significant correlations were observed between changes in microbial populations and fermentation parameters as well as CH4 production:the reductions in methanogen and protozoa popu-lations were directly associated with decreased CH4 production,and the optimized acetate-to-propionate ra-tio further inhibited CH4 generation.Therefore,supplementation with 0.4％XOS can reduce CH4 produc-tion by decreasing the abundances of methanogens and protozoa and optimizing the acetate-to-propionate ratio.These findings provide a novel strategy for mitigating CH4 emissions in ruminants.