Alterations of the rumen bacterial and archaeal communities in growing and finishing beef cattle and its effects on methane emissions

Abstract Text:

The rumen harbors a complex microbial community that is greatly influenced by diet composition.  This microbial community is critical to the survival of the animal and provides up to 80% of the animals’ energy needs.  However, as a by-product the rumen microbial community also produces methane.  The sub-group of methane producing organisms in the rumen are called methanogens.  The interactions between methanogens and the rumen microbial population is dictated by diet.  As a result, the methane being released from cattle will be influenced by the diet being fed to the cattle.  Therefore, evaluating the microbial community composition under different dietary conditions and relating these interactions to methane emissions is critical towards methane mitigation.  To evaluate the effects of diet on microbial community composition and methane emission, 120 animals were fed 10 different growing and 6 finishing diets.  Growing diets included high and low quality forage, with and without monensin supplementation, and different inclusions of modified distillers grains plus solubles (MDGS), and finishing diets contained different fat sources (corn oil, tallow, and distillers) with and without monensin supplementation, and direct fed microbial (DFM).  Microbial community composition and methane emission was monitored.  Methane and CO₂ concentrations of respired air were taken during feeding in an individual feeding facility utilizing 120 individual bunks equipped with the Calan® gate system and an automated gas collection system.  Rumen contents were collected via esophageal tubing for microbial community analysis.  The V3 region of the 16S rRNA gene was sequenced using the Ion Torrent personal genome machine (PGM).  When compared to the respective control diets, the microbial community composition differed in growing and finishing diets.  To further evaluate the microbial community involved in methane emission and performance, correlation analysis was performed using microbial community composition and performance parameters.  This analysis identified many OTUs correlated with methane emission, performance and intake.  This study demonstrates that certain members of the rumen microbial community have a profound effect on animal performance and methane emission.

Keywords: Interactions, methane, microbial community.