Influence of Diet Composition on Cattle Rumen Methanogenesis: A Comparative Metagenomic Analysis in Indian and Exotic Cattle.

Comparative metagenomics approach has been used in this study to discriminate colonization of methanogenic population in different breeds of cattle. We compared two Indian cattle breeds (Gir and Kankrej) and two exotic cattle (Holstein and Jersey) breeds. Using a defined dietary plan for selected Indian varieties, the diet dependent shifts in microbial community and abundance of the enzymes associated with methanogenesis were studied. This data has been compared with the available rumen metagenome data from Holstein and Jersey dairy cattle. The abundance of genes for methanogenesis in Holstein and Jersey cattle came from Methanobacteriales order whereas, majority of the enzymes for methanogenesis in Gir and Kankrej cattle came from Methanomicrobiales order. The study suggested that by using slow/less digestible feed, the propionate levels could be controlled in rumen; and in turn, this would also help in further reducing the hydrogenotrophic production of methane. The study proposes that with the designed diet plan the overall methanogenic microbial pool or the individual methanogens could be targeted for development of methane mitigation strategies.