Amy Biddle
Assistant Professor
Department of Animal & Food Sciences
University of Delaware, Newark, DE
As monogastric obligate herbivores, horses have adapted structural, behavioral, and physiological strategies to gain energy from a marginal, plant based diet, capitalizing on the action of microbial commensals. In addition to other services, these commensals break down and ferment complex plant material, enable access to nutrients, and provide a large amount of energy.
Diet is a major driver of gut microbiome structure and function. Since horses are sensitive to dysbiosis as a result of dietary change, there is a pressing need to understand the structure and function of healthy microbial communities and the mechanisms behind dysbiosis. Realizing the potential of prebiotics and/or probiotics as effective, targeted nutriceuticals depends on a more nuanced and mechanistic understanding of gut microbiome functions and host interactions.
Culture-based experiments and surveys of the equine gut microbiome have identified major phyla of bacteria commonly present: Firmicutes, Bacteroidetes, Fibrobacteres, and Proteobacteria. Community membership associated with forage based diets include a higher abundance of fibrolytic groups: Lachnospiraceae, Ruminococcaceae, and Fibrobacteres, indicating functional specialization in degrading and utilizing a wide range of structural carbohydrates. Horses fed concentrate based diets have gut communities with higher abundances of lactic acid producing and utilizing bacteria Streptococcaceae, Lactobacillaceae, Veillonellaceae, and amylolytic Bacteroidetes, indicating greater functionality in processing nonstructural carbohydrates.