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Prebiotics and Probiotics for Horses: Beneficial or Benign?By Kentucky Equine Research Staff · July 5, 2016

Manufacturers of prebiotics and probiotics suggest that these supplements benefit horses by maintaining or restoring the health of the bacteria, parasites, fungi, and yeast that make up the equine intestinal microbiome. But does science support the use of prebiotics and probiotics in horses? According to recent reviews on the subject, the answer is, unfortunately, not exactly. *,**

“The intestinal microbiome serves several important functions in horses, including producing short-chain fatty acids that serve as a horse’s primary energy source,” explained Kathleen Crandell, Ph.D., a Kentucky Equine Research nutritionist.

Alterations in the microbiome, referred to as dysbiosis, can result in colic and diarrhea, both of which are life-threatening conditions. Thus, the hypothesis that probiotics can compete with disease-causing bacteria, inhibit the absorption of toxins, and stimulate the horse’s immune system is a reasonable suggestion. Examples of commonly fed probiotics include Lactobacillus, Bifidobacterium, and Enterococcus as well as the yeast Saccharomyces. Further, supplementing horses with the substrate, or “food,” that nourishes the probiotic organisms—otherwise known as prebiotic supplements—also makes sense.

Although a small number of studies support the use of probiotics in horses, the bulk of the data shows that probiotics have no effect on diarrhea. In fact, Costa and Weese, preeminent researchers in the field of the equine intestinal microbiome, describe the overall body of evidence supporting the use of probiotics in horses as “disappointing.”

Potential reasons for the discouraging results include lack of information on dosing, choice of organisms being administered, the quality of commercially available products, and whether it is actually possible for live organisms to reach and colonize the large intestine following oral administration.

Regardless of whether studies support supplementation with prebiotics and probiotics in horses or not, the fact of the matter is that these products are extremely popular and included under the umbrella of “generally recognized as safe.” As always, choose your nutritional supplement wisely as not all are created equal.

“Other ways to maintain the equine intestinal microbiome in a healthy state include keeping a steady supply of forage in the diet and, if necessary, using a hindgut buffer, like EquiShure, to keep the pH in a range that is best for the microbiome,” advised Crandell.

*Costa, M.C., and J.S. Weese. The equine intestinal microbiome. Animal Health Research Reviews. 13(1):121-128.

**Coverdale, J.A. 2016. Can the microbiome of the horse be altered to improve digestion? Journal of Animal Science. 94(6):2275-2281.