The microorganisms that populate a horse’s gut are crucial to their health, and essential for the digestion of their fiber-rich diet. Little is known about how differences in this extremely diverse range of microorganisms in the gastrointestinal tract, which scientists call the microbiome, affects the ability of horses to put on and hold weight. For her thesis, University of Delaware doctoral candidate Alexa Johnson is investigating the microbiomes of easy, medium and hard keeper horses.