Comparative Analysis of Rumen Metagenome, Metatranscriptome, Fermentation and Methane Yield in Cattle and Buffaloes Fed on the Same Diet

A study to compare the rumen microbial community composition, functional potential of the microbiota, methane (CH) yield, and rumen fermentation was conducted in adult male cattle and buffaloes fed on the same diet. A total of 41 phyla, 169 orders, 374 families, and 1,376 microbial genera were identified in the study. and were the two most dominant bacterial phyla in both cattle and buffaloes. However, there was no difference in the abundance of and in the rumen metagenome of cattle and buffaloes. Based on the abundance, the was the 3rd largest phylum in the metagenome, constituting 18-20% in both host species. was the most abundant phylum of the methanogens, whereas and were the most abundant orders and genera in both species. The methanogen abundances were not different between the two host species. Like the metagenome, the difference between the compositional and functional abundances (metagenome vs. metatranscriptome) of the and was not significant, whereas the proteobacteria were functionally less active than their metagenomic composition. Contrary to the metagenome, the was the 3rd most functional phylum in the rumen and constituted ~15% of the metatranscriptome. were the most functional methanogens, accounting for more than 2/3rd of the total archaeal functionality. These results indicated that the methanogens from were functionally more active as compared to their compositional abundance. The CH yield (g/kg DMI), CH emission (g/kg DDM), dry matter (DM) intake, and rumen fermentation did not vary between the two host species. Overall, the study established a substantial difference between the compositional abundances and metabolic functionality of the rumen microbiota; however, feeding cattle and buffaloes on the same diet resulted in similar microbiota composition, metabolic functionality, and CH yield. Further studies are warranted to investigate the effect of different diets and environments on the composition and metabolic functionality of the rumen microbiota.