Rumen bacterial cluster identification and its influence on rumen metabolites and growth performance of young goats

Enterotypes,which are defined as bacterial clusters in the gut microbiome,have been found to have a close relationship to host metabolism and health.However,this concept has never been used in the rumen,and little is known about the complex biological relationships between ruminants and their rumen bacterial clusters.In this study,we used young goats(n=99)as a model,fed them the same diet,and analyzed their rumen microbiome and corresponding bacterial clusters.The relationships between the bacterial clusters and rumen fermentation and growth performance in the goats were further investigated.Two bacterial clusters were identified in all goats:the P-cluster(dominated by genus Prevotella,n=38)and R-cluster(dominated by Ruminococcus,n=61).Compared with P-cluster goats,Rcluster goats had greater growth rates,concentrations of propionate,butyrate,and 18 free amino acids)and proportion of unsaturated fatty acids,but lower acetate molar percentage,acetate to propionate ratio,and several odd and branched chain and saturated fatty acids in rumen fluid(P<0.05).Several members of Firmicutes,including Ruminococcus,Oscillospiraceae NK4A214 group,and Christensenellaceae R-7 group were significantly higher in the R-cluster,whereas Prevotellaceae members,such as Prevotella and Prevotellaceae UCG-003,were significantly higher in P-cluster(P<0.01).Co-occurrence networks showed that R-cluster enriched bacteria had significant negative correlations with P-cluster enriched bacteria(P<0.05).Moreover,we found the concentrations of propionate,butyrate and free amino acids,and the proportions of unsaturated fatty acids were positively correlated with R-cluster enriched bacteria(P<0.05).The concentrations of acetate,acetate to propionate ratio,and the proportion of odd and branched chain and saturated fatty acids were positively correlated with P-cluster enriched bacteria(P<0.05).Overall,our results indicated that rumen bacterial clusters can influence rumen fermentation and growth performance of young goats,which may shed light on modulating the rumen microbiome in early life to improve the growth performance of ruminant animals.