Effects of different molecular weights of chitosan on methane production and bacterial community structure in vitro

摘要

cqvip:As a new feed additive,chitosan has been shown in recent years to have a certain role in reducing methane emissions from the gastrointestinal tracts of ruminants.However,the effects of chitosan with different molecular weights on rumen ferme ntation,methane production and bacterial comm unity structure are not yet clear.A basal diet without chitosa n served as the control(CTL),and the treatment diets were supplemented with chitosan with different molecular weights:1000(1K),3000(3K),5000(5K),50000(5W)and 200000(20W)dry matter(DM).Six fermentation units per treatment were established.Gas chromatography was used to measure the co nee ntrations of metha ne,H2 and volatile fatty acids(VFAs).The bacterial 16S rRNA genes were sequeneed with an Illumina MiSeq platform and analysed to reveal the relative abunda nces of bacterial community taxa.The results showed that the propi onate proporti on was sign ifica ntly in creased by the addition of chitosan with different molecular weights(P<0.05),while methane production and the acetate proportion were significantly decreased(P<0.05).The relative mbundances of Rikenellaceae_RC9_gut_group and Prevotellaceae_UCG_003 were significa ntly in creased in the 3K chitosa n group compared with the CTL group,whereas the relative abunda nee of Ruminococcaceae_NK4A214_group was significantly decreased(P<0.05).Correlation analyses of the relative abundances of the bacterial genera showed that Prevotella was positively related to propionmte production(Pv0.05).In conclusion,3K chitosan could reduce methane production by replacing fibrolytic bacteria(Firmicutes and Fibrobacteres)with amylolytic bacteria(Bacteroidetes and Proteobacteria)in the bacterial community structure.