Diet influences microbial community composition, and methane emission in growing and finishing beef cattle
Methane production in ruminants via enteric fermentation is dependent on the microbial community within the ruminant animal. The microscale processes of this microbial community are greatly influenced by diet. However, the interactions between diet, microbial community composition, and methane emission are poorly understood. To better understand how diet influences microbial community structure and methane emission, methane/ CO2 ratio and microbial community composition were evaluated in animals 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 a 84-day growing trial, followed by a 125-day finishing trial that evaluated four different fat sources (corn oil, tallow, MGDS, corn-no oil) and monensin supplementation. Methane and CO2 measurements were made during feeding using an individual feeding facility that contained 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 the effects of diet on methane emission. Samples were collected for microbial community analysis via stomach tubing, and the microbial community structure was analyzed by sequencing the 16S rRNA gene. In growing cattle and finishing cattle, microbial community structure (both archaea and bacteria) and methane levels were similar in all animals on the common diet. In growing cattle, diet quality (high vs low quality forage) 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, but the microbial community composition did change significantly. In finishing cattle, methane levels were highest in MDGS diets and significantly decreased (P<0.05) in corn control diet and 3% tallow diets. The microbial community did not show significant changes in total microbial community structure during supplementation of different fat sources. These data suggest dietary intervention can be used in growing cattle 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.
Microbial community, methane, Archaea