THE EFFECT OF DIET ON THE BOVINE RUMEN MICROBIAL COMMUNITY STRUCTURE AND COMPOSITION AND ITS EFFECTS ON METHANE PRODUCTION IN GROWING AND FINISHING CATTLE

Methane is a potent greenhouse gas (GHG) that contributes to global warming. A natural by-product of ruminant fermentation is the production and eructation of methane. Methane is produced by a small unique group of microorganism’s called methanogens that belong to the domain Archaea. Enteric methane represents 2-12% energy loss in ruminants. It is well established that diet affects the microbial community structure and composition. Fermentative products of the mixed microbial population (bacteria, fungi, and protozoa) become the substrates for methanogens. These substrates influence which microorganisms will thrive. However, the effect of diet on the microbial community while simultaneously calculating methane production by expired breath sample from the cattle has never been explored. Two studies were conducted under commercial feedlot production systems. A growing study utilizing 120 steers placed initially on a common diet and then transferred to various growing diets observing the effects of forage quality, MDGS supplementation, with or without Rumensin® (Elanco Animal Health, Greenfield, IN). Community structuring was observed between amounts of MDGS supplementation and forage quality. A finishing study was also conducted utilizing 60 steers placed on a common diet followed by various finishing diets. Finishing diets evaluated the effect of DRC or MDGS supplementation, lipid additions, with and without Rumensin®. Community structuring was observed between DRC and MDGS supplementation however, structuring due to lipid addition was not observed. Utilizing dietary intervention strategies to mitigate methane production may be more suited to the growing phase rather than the finishing phase. Advisor: Samodha Fernand