Age, stress, and health problems can all affect the horses gut microbiome. | Adobe StockPostbiotics provide beneficial compounds typically supplied by the microbes that live in the horses hindgut. Providing postbiotics directly to the horse, bypassing the microbiome, when a horses hindgut is stressed, compromised, or in need of consistent daily support will help improve his overall health, said Liz Schatz, DVM, staff veterinarian for SmartEquine, during her presentation at the 2026 EquiSUMMIT Equine Nutrition & Health Conference, hosted by Kemin Industries.The Equine Gastrointestinal MicrobiomeThe intestinal microbiome is a community of microorganisms living in the gastrointestinal tract that essentially behaves like its own organ system, said Schatz. In addition to the trillions of bacteria, the intestinal microbiome is also composed of archaea, fungi, protozoa, viruses, and parasites. The more diverse the microbe population, the more resilient and capable of adapting to various stresses, such as diet change.The hindgut, which consists of the cecum and large colon (or large intestine), absorbs water and nutrients and ferments structural (complex) carbohydrates for energy, also houses about 70% of the horses immune system. Its microbiome maintains the integrity of the gut and reduces pathogen overgrowth.Factors Affecting the Horses GI MicrobiomeMany things can affect the microbiome, including age, stresses such as transport or competition, health status (e.g., equine metabolic syndrome), diet changes, forage quality, high-grain diets, and medications such as antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), and dewormers, said Schatz.Disruptions in the gut microbiome, a condition called dysbiosis, can lead to loose stool, colic (abdominal pain), colitis (inflammation of the colon), weight loss, behavior issues via the microbiome-gut-brain axis, and laminitis.Microbiome-Gut-Brain Axis in HorsesSchatz said the nervous, immune, and endocrine systems interconnect like a communication network in constant dialogue.What this means for your horse is that dysbiosis can contribute to behavior changes such as anxiety, spookiness, and even stereotypies such as weaving, cribbing, and stall walking, she explained. In turn, stress can alter the microbiome, meaning this can become a vicious cycle unless we intervene.Defining Pre-, Pro-, and PostbioticsPrebiotics are nondigestible fibers such as mannanoligosaccharides and inulin that feed the beneficial bacteria in the horses hindgut, Schatz explained.On the other hand, probiotics are the actual live beneficial microorganismsusually yeast or bacteriathat add microbes to the hindgut.Finally, postbiotics are nonliving beneficial byproducts of normal microbial fiber fermentation in the hindgut, she added. They include volatile fatty acids, cell fragments, peptides, vitamins (B and K), and immune-modulating compounds. These deliver direct biological benefits, such as maintaining intestinal barrier integrity, without having to rely on live microbes.In other words, prebiotics feed the good bugs, probiotics add more good bugs, and postbiotics provide the benefit of the good bugs, said Schatz.Why Feed Horses Postbiotics?Microbes in a healthy hindgut produce postbiotics all the time. However, modern horse management, as mentioned above, can negatively affect the microbial community, decreasing postbiotic production. Postbiotic supplements deliver the benefits of a healthy microbiome without relying on the live organisms its like a system bypass, said Schatz.Which horses benefit from postbiotics? Schatz listed the following:Any horses for proactive, daily support, because postbiotics provide benefits regardless of the gut conditionsHorses under stress, to support gastrointestinal and immune health after microbiome disruptionHorses receiving medications such as antibiotics, NSAIDs, and dewormers, to support gut lining and immune function when good bugs might be compromisedHorses with chronic loose stool or free fecal water syndrome, to help support the hindgut environment as well as intestinal barrier integritySenior horses with age-related digestive challenges, to deliver immune and digestive benefits of microbial fermentationHard keepers, for improving nutrient utilization and digestive efficiencyHorses with allergy/immune challenges, to help balance immune responseAlmost any horse can benefit from postbiotics, and they can work together with the pre- and probiotics, said Schatz.Take-Home MessageA healthy hindgut naturally produces postbiotics through fiber fermentation. Stress, age, and modern management practices can reduce this process. Supplying postbiotics directly helps support digestion, immunity, and gut integrity when the microbiome cannot perform optimally on its own.