18 Role of the Rumen Microbiome in Beef Cattle Gut Physiology and Performance

The diverse rumen microbiome converts low-quality feedstuffs into usable energy and provides approximately 70% of the energy required by its ruminant host through fermentation byproducts. Due to microbial impacts on host health and productivity, numerous studies have associated rumen microbiome variation with important sustainability phenotypes, such as feed efficiency and methane emissions. Although diet, genetics, and environment contribute to variation in feed efficiency, selection for feed-efficient beef cattle using genetic improvement technologies has helped to understand and improve the persistence and longevity of such phenotypes within the herd. While diet has been considered to be the primary driver for the composition and structure of the rumen microbiome, recent studies have indicated the microbial communities present in the rumen are under low-to-moderate host genetic control. The mutualistic, commensal, and parasitic microorganisms that reside in the rumen and lower gastrointestinal tract of cattle and other ruminants exert enormous influence over animal physiology and performance. The ability to interrogate these systems at great depth has permitted a greater understanding of the microbiological and molecular mechanisms involved in ruminant nutrition and health. The work in our group in the field of beef cattle gut microbiology, as it relates to feed efficiency, permits the exploration of these critical microbial community networks. This knowledge will aid researchers seeking to address the grand challenge of maintaining host-efficient gut microbiomes throughout cattle production operations. This work is supported by the Agriculture and Food Research Initiative grant no. 2020-67015-30832 from the USDA National Institute of Food and Agriculture.