Feed digestion in horses is largely accomplished by microbial fermentation in the hindgut. The cecum and colon provide an environment that promotes the digestion and absorption of nutrients from fibrous products such as hay and beet pulp. Disrupting the microbe balance, due to mismanaged feeding practices or illness, can have detrimental effects on the horse’s health. Thus, some horse owners and veterinarians use pre- and probiotics to help keep the microbial balance in check and the horse’s digestive tract functioning properly.

Prebiotics are food components that stimulate hindgut microflora activity and growth. The horse does not digest these ingredients; rather, hindgut microbes do. These include carbohydrate fibers such as fructo-oligosaccharides and manno-oligosaccharides. Premium feed products include several prebiotics, including yeast cultures and fungi, to aid in digestion.

Probiotics, or direct-fed microbials, are the bacteria and entercoli typically found in the horse’s intestinal lumen. The goal in feeding a probiotic supplement is to enhance the hindgut’s microbial population and reduce the growth of potentially harmful bacteria.

Probiotics on the market today include live bacterial cultures and live yeast cultures. Equine probiotics typically include Lactobacillus and Bifidobacterium species of bacteria and/or the yeast Saccharomyces boulardii.

To date, there is little scientific evidence to support–or negate–claims of enhanced microbial protection using probiotics. However, improved changes in microbial fermentation and fiber digestibility have been reported both <