The horse’s gastrointestinal tract is sensitive to change, so horse owners are consistently seeking ways to better support it during times of stress and transition. Various dietary supplements have gained popularity, but it can be daunting to figure out which products are worth the investment.

What are Pre-, Pro- and Postbiotics?

The World Health Organization defines probiotics as live microorganisms that confer a health benefit to the host when administered in the correct amounts. “Of the three terms (pre-, pro- and postbiotics), probiotics are the only product that has live microorganisms,” says Jamie Kopper, DVM, PhD, Dipl. ACVIM, Dipl. ACVECC, assistant professor of veterinary clinical studies at Iowa State University, in Ames. “Prebiotics, in theory, help keep probiotics alive by providing them with nutrition, and postbiotics refer to anything that is left over after the horse has digested the pre- and probiotics.”

In other words, prebiotics are essentially feed materials for the live microorganisms that make up probiotics, typically fiber. Postbiotics are what is left over, which is often a variety of vitamins, short-chain fatty acids, and various polysaccharides that can be beneficial to the horse. “Another good term to be aware of is proteobiotics, which refers to protein peptides (short chains of amino acids found in the body, foods, and supplements) produced by probiotics—there is not much research in the equine world on these yet, but they (refer) to things such as anti-inflammatory peptides and antimicrobial peptides,” adds Kopper.

Should I Feed These to My Horse?

Based on the lack of conclusive research and the multitude of products available, knowing which products to select can be very difficult. “We do not have the recommendation for feeding horses these supplements,” says Kopper. “There is a lot of work that has been done in humans both to identify ideal microorganisms to improve human intestinal health as well as the minimum number of organisms that are needed to expect a benefit.”

Horse owners should bear in mind their horses have different needs from humans due to their unique gastrointestinal physiology. “For example, Lactobacillus is a common (bacterium) included in human probiotics,” says Kopper. “In healthy horses, Lactobacillus is present in very low numbers and actually increases in horses with diarrhea, which makes me question if it’s something we should really be (supplementing in) horses—but the truth is that we just don’t know at this time.”

Pre-, Pro-, and Postbiotic Research in Horses

Probiotic-based equine supplements remain popular despite limited supporting research available. “My advice to horse owners would be to select products (whether they are pre-, pro- or postbiotics) based on research that the manufacturer has conducted on the product,” says Wendy Pearson, PhD, associate professor of equine physiology at the University of Guelph, in Ontario, Canada.

Over a roughly 19-year period, researchers have investigated label claims on probiotic supplements and found major discrepancies. “Lots of products claim to be ‘science based,’ but the vast majority do not have objective research (in) horses,” says Pearson.

This lack of research can create risk for horses because there is no way for owners to know what supplements are beneficial vs. harmful. “I am not aware of any toxicity reports in mature horses when using pre-, pro-, or postbiotic supplements, however a 2021 review paper concluded that the evidence for efficacy in horses is weak,” says Pearson.

However, this is an area of science that is growing, and there are some reports of positive benefits with certain products. “We have recently reported that a combination of probiotic/prebiotic supplement protected horses from microbiome changes associated with antibiotic use,” says Pearson. “The same product strongly increased short-chain fatty acid production by cecal microbiota in vitro (in the live horse), which supports a prebiotic effect of the supplement.”

Practical Methods for Assessing Pre-, Pro-, and Postbiotic Supplements for Horses

Kopper recommends that horse owners read the labels of products they are considering with a critical eye and note the following:

• Is everything spelled correctly on the label?
• Does the label list specific bacteria or yeast?
  • The label should not be vague. For example, it should use descriptions such as Enterococcus faecium instead of “probiotic blend” or “lactic-acid-producing bacteria.”
• The label should list how much of each yeast or bacterium is supposed to be in the product in a measurement called CFU (colony-forming unit).
  • A high-quality product will include a description such as “Enterococcus faecium—10,000,000 CFU/gram.”
• The label should state the storage instructions. Bacteria and yeast cannot live under all circumstances, so the more specific the instructions, the better.
• The label should provide an expiration date.

Also reach out to the manufacturer to inquire about any research that has been done on the product.

Take-Home Message

Overall, understanding what pre-, pro-, and postbiotics are, the current research, and potential risks can help you decide if they might be a beneficial addition to your horse’s diet. Kopper’s and Pearson’s practical recommendations can help horse owners investigate the various products available. However, work with your veterinarian and an equine nutritionist to ensure you are buying the best product for your horse.