Changes in the predicted function of the rumen bacterial community of Japanese Black beef cattle during the fattening stages according to Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses

We investigated changes in the predicted functions of the rumen bacterial community in Japanese Black beef cattle during fattening. Nine cattle were fed a high-concentrate diet during the early, middle, and late fattening stages consecutively (10–14, 15–22, and 23–30 months of age, respectively). The rumen fluid and solid samples collected at each stage were subjected to sequencing analyses. The sequencing results were clustered and classified into operational taxonomic units (OTUs). Representative sequences and a raw counting table for each OTU were submitted to the Piphillin website. The predicted functions were revealed by the Kyoto Encyclopedia of Genes and Genomes database as the ratio of the total sequence. In the early stage, “Biosynthesis of secondary metabolites” was significantly higher in the fluid fraction than in the solid fraction. “Two-component system” in the middle stage was significantly lower and “Purine metabolism” in the late stage was significantly higher in the fluid fraction than those in the solid fraction. The fluid fraction was significantly correlated with acetic acid, propionic acid, and bacterial metabolism, such as “Biosynthesis of secondary metabolites” and “Sugar metabolism.” Moreover, the solid fraction was correlated with “Purine metabolism” and “Biosynthesis of secondary metabolism”. These results suggest that the rumen bacterial community in Japanese Black beef cattle adapts to changes in rumen conditions by altering their functions in response to a long-term high-grain diet.