Diversity Analysis of Rumen Fiber-Degrading Bacteria in Dairy Cows Enriched with Different Fiber Sources
The aim of this experiment was to investigate the changes in the diversity of rumen fiber-degrading bacteria in dairy cows enriched with different fiber sources.The experiment was conducted in a completely ran-domized design and divided into four groups,namely,control group without carbon source(CK group),sodi-um carboxymethylcellulose group(CMC group),microcrystalline cellulose group(MCC group)and What-man No.1 filter paper group(WN group),with six replicates in each group.In vitro rumen fermentation tests were carried out to study the effects of different fiber sources on fermentation parameters and microflora struc-ture.The results showed as follows:1)the pH in both MCC and WN groups was significantly lower than that in CK and CMC groups(P＜0.05).The concentrations of acetic acid,butyric acid and valeric acid as well as the acetic acid to propanoic acid ratio in all experimental groups were significantly higher than those in CK group(P＜0.05);the isobutyric acid concentration in CMC group was significantly higher than that in CK group(P＜0.05);the concentrations of propionic acid,isobutyric acid and total volatile fatty acids in MCC group were significantly higher than those in CK group(P＜0.05),and the isovaleric acid concentration was significantly lower than that in CK group(P＜0.05);the concentrations of propionic acid and total volatile fat-ty acids in WN group were significantly higher than those in CK group(P＜0.05),and the isovaleric acid con-centration was significantly lower than that in CK group(P＜0.05).2)In a diversity analysis,the indices of Chaol,Sobs,Simpson,Shannon,Pielou_e and PD in MCC and WN group were significantly lower than those in CK and CMC groups(P＜0.05).At the phylum level,the Firmicutes relative abundance in all experi-mental groups was significantly higher than that in CK group(P＜0.05),and the relative abundances of Bacte-roidetes and Synergistetes were significantly lower than those in CK group(P＜0.05);the Fibrobacteres rela-tive abundance in MCC group was significantly higher than that in the other experimental groups and CK group(P＜0.05).At the genus level,the relative abundances of Bacteroides,Pyramidobacter and Oscillospira in all experimental groups were significantly lower than that in CK group(P＜0.05);the Clostridium relative abun-dance in CMC group was significantly higher than that in CK group(P＜0.05),and the relative abundances of Prevotella and Succiniclasticum were significantly lower than those in CK group(P＜0.05);the relative abun-dances of Lachnospira,Clostridium,Ruminococcus,Prevotella and Fibrobacter in MCC group were signifi-cantly higher than those in CK group(P＜0.05),and the relative abundances of Succiniclasticum and Bu-tyrivibrio in MCC group were significantly lower than those in CK group(P＜0.05);the relative abundances of Lachnospira and Ruminococcus in WN group were significantly higher than those in CK group(P＜0.05),and the Butyrivibrio relative abundance was significantly lower than that in CK group(P＜0.05).3)The Bac-teroides relative abundance had a significant negative correlation with concentrations of acetic acid and valeric acid(P＜0.05);the relative abundances of Lachnospira and Ruminococcus had a significant positive correla-tion with the concentrations of acetic acid,butyric acid and total volatile fatty acids(P＜0.05),and had a sig-nificant negative correlation with the isovaleric acid concentration and pH(P＜0.05);the Clostridium relative abundance had a significant positive correlation with the isobutyric acid concentration(P＜0.05);the Prevotel-la relative abundance had a significant positive correlation with the propionic acid content(P＜0.05).In con-clusion,the highest degradation rate of Whatman No.1 filter paper was achieved by the rumen fiber-degrading bacteria in dairy cows;the preference of rumen fiber-degrading bacteria in dairy cows for different fiber sources varies markedly,with sodium carboxymethylcellulose being enriched for Clostridium,microcrystalline cellulose being enriched for Fibrobacter,and Whatman No.l filter paper being enriched for Ruminococcus.[Chinese Journal of Animal Nutrition,2024,36(11):7068-7080]
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