Nutrition's Role In Equine Gut Dysbiosis

What is gut dysbiosis?

Equine gut dysbiosis refers to an imbalance in the microbial populations of the gastrointestinal tract, particularly within the hindgut, where trillions of microorganisms ferment fiber and produce short-chain fatty acids that supply an estimated 60–70% of a horse's daily energy requirements. Dysbiosis can be severe and life threatening if not addressed by good equine management practices.

What causes dysbiosis in the horse's gut?

Dysbiosis can be caused by a variety of problems including:

• Dietary problems

• Nutrient deficiencies such as lack of forage

• Antibiotics

• Sugars and starches

• NSAIDs when used repeatedly

• Mycotoxins (mold often in feed and hay)

• Stress/environment

• Parasite overload

• Dewormers

• Abrupt dietary changes

What is does a horse's nutrition have to do with gut dysbiosis?

Nutrition plays a central role in maintaining microbial balance because horses must consume a continuous, forage-based diet rich in structural carbohydrates. Research has demonstrated that diets high in forage support greater microbial diversity and stability, while abrupt dietary changes or excessive starch intake can disrupt normal microbial populations. This disruption can decrease beneficial fiber-fermenting bacteria, alter hindgut pH, and impair fermentation efficiency, ultimately reducing nutrient utilization and compromising gastrointestinal health.

Current evidence suggests that high-starch, high sugar, low-fiber feeding practices are among the most significant nutritional risk factors for equine gut dysbiosis. When starch escapes digestion in the small intestine and enters the hindgut, rapid fermentation can increase lactic acid production, lower hindgut pH, and promote microbial shifts associated with hindgut acidosis, colic, laminitis, inflammation, and poor performance. Studies comparing high-fiber and high-starch diets consistently show that fiber-based feeding programs support a healthier and more resilient microbiome, whereas starch-heavy diets reduce microbial diversity and increase the likelihood of dysbiosis. Consequently, nutrition strategies focused on consistent forage intake, gradual feed transitions, and controlled starch consumption are widely recommended to promote optimal gut health and microbial stability in horses.

Overdoing pre and probiotics and supplements is also a major contributor. Many feed programs do not yield a "balanced diet" and too much of certain nutrients or additives can cause dysbiosis over time. Too many probiotics in the microbiome for example, will cause major disruption which can ultimately lead to illness. Not all equines require additional supplementation of certain nutrients.

What happens to a horse with gut dysbiosis?

Gut dysbiosis, if unaddressed, can lead to malabsorption of nutrients, leaky gut syndrome, colic, gastric ulcers, and even laminitis.

How can we treat gut dysbiosis?

Equine owners can address gut dysbiosis by evaluating the horse's diet and medications carefully. A strategic functional nutrition program paired with safe management practices is key to overcoming dysbiosis and preventing it from recurring.

• Forage-first diet is key to success.

• Reduce starch and sugar.

• Balance all nutrients -- vitamins and minerals.

• Use prebiotics and probiotics with caution.

• Always read the label to ensure feeds and supplements do not have additives, soy, parabens, artificial sweeteners, alcohol, etc.

Need help with dysbiosis or preventing it? Hilltop Equine Concepts can help you formulate a safe, balanced diet for your horse using functional nutrition practices where food is more than fuel. It's medicine.

Sources:

• Kauter A, Epping L, Semmler T, et al. (2019). The gut microbiome of horses: current research on equine enteral microbiota and future perspectives. Animal Microbiome, 1, 14.

• Wunderlich G, Bull M, Ross T, et al. (2023). Understanding the microbial fibre degrading communities & processes in the equine gut. Animal Microbiome, 5, 3.

• Dougal K, de la Fuente G, Harris PA, et al. (2017). The Impact of Diet on the Hindgut Microbiome. Journal of Equine Veterinary Science, 52, 23–28.

• Raspa F, Vervuert I, Capucchio MT, et al. (2022). A high-starch vs. high-fibre diet: effects on the gut environment of the different intestinal compartments of the horse digestive tract. BMC Veterinary Research, 18, 187.

• Bulmer LS, Murray JA, Burns NM, et al. (2019). High-starch diets alter equine faecal microbiota and increase behavioural reactivity. Journal of Animal Science, 97(4), 1488–1498.

• Lavoie-Lamoureux A, Costa MC, et al. (2024). Current Understanding of Equine Gut Dysbiosis and Microbiota Manipulation Techniques: Comparison with Current Knowledge in Other Species. Animals, 14(5), 758.

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