NC Horse Council

Equine Health

What probiotics are recommended for performance horses and do they work?

(This question was submitted by Mrs. Cathy Heaton, a member of the North Carolina Arabian Horse Association. Would you like to ask a question and see your question answered in our next newsletter? You can submit your question to: suegray@nchorsecouncil.com)

Probiotics, also known as direct-fed microbial or DFMs, are dietary supplements containing live naturally occurring microorganisms (bacteria, fungi and/or yeast). The microorganisms are intended to arrive alive in the hindgut (the part of the digestive tract that comes after the small intestine), establish residence and do good things. The concept of probiotics originated about 100 years ago when a Nobel Prize winning scientist suggested that beneficial bacteria from yogurt could colonize the gut, displacing pathogenic (disease-causing) bacteria and extend the life of the yogurt eaters! Indeed, the lactobacillus bacteria, like those found in yogurt, are still the most popular probiotic species.

In addition to displacing pathogens, probiotics may help regulate the conditions in the horse's gut tract. The grass and legumes in your horse's diet are mostly made up fiber. Horses cannot digest fiber and, instead, rely on the microorganisms that live in their hind gut to breakdown the cellulose and convert it to volatile fatty acids which can be absorbed and used by the horse for energy. Probiotics may promote conditions that favor the growth of fiber digesting microbes, allowing the horse to extract more energy from his diet.

The microorganisms in probiotics produce various compounds as part of their life processes. These include organic acids, vitamins, amino acids, enzymes and antibiotics. All of these by-products end up in the material they are grown (fermented) in. This fermentation product is part of the probiotic supplement. With certain less hardy species, the fermentation product with dead microbes may be sold as a supplement. Technically, this is not a probiotic.

Performance horses are in a state of stress from exercise, from transport, and, often, from their diet which is relatively high in grain and low in fiber. These factors can affect the fermentation process and also render the horse more susceptible to gut pathogens.

There are well over 100 DFM's listed for horses in the "Direct-Fed Microbial, Enzymes & Forage Additive Compendium." Most have no objective research to support their use. The FDA puts DFM's in a class called "generally recognized as safe" or GRAS. This designation means the FDA believes these products cause no harm. It does not mean they do any good. DFM's cannot legally claim to treat any disease or condition, establish viable colonies in the gut, or affect any structure or function of the animal.

The potential for benefit from feeding probiotics to performance horses certainly exists, but hard evidence is in short supply. There is not much economic incentive for the DFM suppliers to fund research, since they can sell their products based on customer testimonials and data from other species. This type of research on existing microorganisms would almost certainly have to be funded by horse owners.

John E. Thomson, Ph.D., PAS
Nutritionist & Procurement Manager
Wilson Milling LLC