Best Probiotic and Prebiotic Supplements for Horses

Probiotic supplements contain live beneficial microorganisms that support a healthy gut microbiome. In horses, probiotics are used to support microbial balance in the hindgut, contribute to fiber fermentation, and maintain digestion and immune function. They are especially useful during periods of stress, illness, dietary changes, or antibiotic use when natural microbial populations may be disrupted. Probiotics may also be recommended in horses experiencing occasional bowel disruptions or diarrhea.

Probiotics help maintain a balanced hindgut microbiome, which is essential for digesting fiber, producing B-vitamins, and supporting immune and metabolic health. In horses, probiotics can help improve manure consistency, reduce the risk of digestive upset, and enhance nutrient absorption. They may also support recovery after antibiotic use, gastric ulcer treatment, or periods of stress.

Horses may benefit from probiotics during times of stress, illness, dietary change, or when digestive issues are present. Signs that probiotics may help include loose manure, weight loss, poor appetite, inconsistent condition despite adequate feed, digestive discomfort, or after antibiotic use. Probiotics may also support older horses, hard keepers, or those in regular training and travel. For personalized guidance, submit a free diet evaluation to consult with our equine nutritionists.

Mad Barn’s Optimum Probiotic contains a blend of five live bacterial strains selected for their stability, survivability, and ability to support equine digestive health:

• Lactobacillus acidophilus
• Lactobacillus fermentum
• Lactobacillus casei
• Lactobacillus plantarum
• Lactobacillus farciminis

These strains are known for their ability to survive passage through the stomach and reach the hindgut, where they help maintain a balanced microbiome, support fiber fermentation, and promote normal digestive function.

CFU stands for "colony-forming units" and is a measure of the number of live, viable microorganisms in a probiotic supplement. A higher CFU count indicates a greater concentration of beneficial bacteria. Mad Barn’s probiotic supplements contain a minimum of 20 billion CFUs per serving, using strains that are known to support gut health in horses.

The five bacterial strains found in our Optimum Probiotic supplement (Lactobacillus acidophilus, L. fermentum, L. casei, L. plantarum, and L. farciminis) are resistant to stomach acid, bile, and digestive enzymes. This means a high proportion of live microbes survive transit and reach the horse’s hindgut where they can support microbial balance and digestive health.

Most horses see initial results from feeding probiotic supplements within two weeks, depending on the reason for use. Horses experiencing recent antibiotic use, digestive upset, or stress may require short-term support, while others, such as seniors, hard keepers, or those in consistent training, may benefit from long-term use to maintain digestive and hindgut health.

Because digestive health is an ongoing need, many horse owners choose to feed probiotics daily. That’s why we priced our Optimum Probiotic at only $10 per month, making it affordable to keep horses on the supplement long-term as part of a daily routine.

Prebiotics are specialized non-digestible fibers that feed and promote the growth of beneficial bacteria in the gut. In horses, prebiotics support the health of the hindgut microbiome by enhancing fermentation activity and helping to stabilize microbial populations. They are often included in gut health supplements alongside probiotics to improve efficacy.

Prebiotics are non-digestible fibers or substrates that selectively nourish beneficial microbes in the hindgut, helping to promote a stable microbial community and healthy fiber fermentation.

In horses, prebiotics support fiber digestion, energy metabolism, manure consistency, digestive comfort, immune function, and protection from absorption of toxins. Prebiotic supplements also have synergistic effects with probiotics, resulting in more effective gut support.

Although horses naturally consume a high amount of dietary fiber from forage, which itself acts as a broad-spectrum prebiotic, targeted prebiotic supplements can provide added benefits beyond what forage alone delivers. For example, Optimum Digestive Health includes mannooligosaccharides (MOS) and beta-glucans that support microbial growth and help bind toxins.

These compounds help optimize hindgut fermentation, stabilize the microbiome, and support overall digestive efficiency, especially in horses under stress, recovering from digestive upsets, or with compromised hindgut balance.

If your horse has a healthy digestive system and you're looking to maintain gut balance through everyday changes in diet, travel, or training, a daily-use product like Optimum Probiotic may be sufficient. It provides a concentrated blend of five pure probiotic strains to support the hindgut microbiome, digestion, and immune function.

Horses with more complex digestive concerns, such as loose manure, sensitivity to feed changes, history of colic, or poor nutrient absorption, may benefit from additional support. Optimum Digestive Health combines probiotics with prebiotics, yeast, digestive enzymes, and toxin binders to maintain a healthy gut environment and support digestive function.

For help choosing the best option for your horse, you can submit a free diet evaluation and speak with one of our equine nutritionists.