Probiotics have been used by people for at least a century to promote good health. Hard scientific evidence has proven that probiotics can be beneficial to humans. As it so often does, the horse world saw this good thing and adapted it to equine uses. But there’s one difference: Solid research proving probiotics’ worth to horses is missing, even though they have tremendous backing from anecdotal evidence. Here, we sift some of the wheat from the chaff to help expose the facts, the hypotheses, and the potential myths surrounding probiotic use in horses.

It Starts With Microbes

To understand the basic intent of probiotic use, it helps to understand the role of beneficial microorganisms in the horse’s digestive system. A variety of beneficial bacteria live throughout the equine gastrointestinal tract, with the highest numbers concentrated in the cecum and large intestine, explains Scott Weese, DVM, DVSc, Dipl. ACVIM, assistant professor of clinical studies at the University of Guelph’s Ontario Veterinary College.

These microbes assist in the digestive process. In particular, they help the horse’s gut break down the glucose bonds in insoluble carbohydrates, which come from the plants (hay, grass, grains) that horses eat. Without the microbes, your horse couldn’t effectively digest these products