Prebiotics and probiotics are fed with the goal of helping to keep the bacteria in your horse’s gastrointestinal (GI) tract healthy. One way they may do this is by helping the beneficial bacteria in the gut flourish and function. They accomplish this in two unique ways. Prebiotics are often specialized fibers or complex carbohydrates — not living microorganisms — that act as a food or energy source for the beneficial bacteria in the GI tract. Probiotics on the other hand are live microorganisms — usually strains of beneficial bacteria or “good bugs” that can help improve gut health.