Effect of diet on microbial community composition, and methane emission in growing beef cattle

Abstract Text:

Methane levels in the atmosphere have tripled since pre-industrial times. Among the major sources of methane production, ruminants account for a considerable fraction of the anthropogenic methane produced. At the heart of anaerobic methane production in ruminants is a microbial food chain. The microscale processes of this microbial food chain are greatly influenced by diet. However, the interactions between diet, microbial community composition, and methane emission are poorly understood. Thus, to better understand these interactions, we have evaluated methane emission and microbial community composition on a common diet and under different dietary conditions (high and low quality forage, with and without monensin supplementation, and different levels of modified distillers grain plus solubles (MDGS) supplementation) in growing cattle. Methane and CO₂ measurements were made during feeding using an individual feeding facility; 120 individual bunks equipped with the Calan® gate system and an automated gas collection system. Gases were analyzed using a mobile GC unit. CO₂ was used as an internal standard and the methane/CO₂ ratio was used to determine dietary effects on methane emission. Samples were collected for microbial community analysis via stomach tubing, and the microbial community structure was analyzed using the Ion Torrent personal genome machine (PGM) by sequencing the 16S rRNA gene. Microbial community structure and methane levels were similar in animals on the common diet and changed when different diets were fed. Diet quality (high vs low quality forage) and level of MDGS supplementation (20% vs. 40%) significantly influenced (P < 0.05) the methane/CO₂ratio and the microbial community composition, where high quality forage produced higher levels of methane. However, the level of methane emitted did not change by level of supplementation. These data suggest dietary intervention can be used to change microbial community structure, which in turn can affect methane emission levels. Identifying the members of the rumen microbial community from high and low methane emitting cattle and diets would help identify microbial community members that influence methane production in cattle, which may lead to dietary and other intervention strategies to change these microbial populations in the rumen.

Keywords: Microbial community, methane