Probiotics are everywhere in the horse world. Powders, pastes, feed-throughs, “digestive balancers,” and daily supplements all promise the same thing: a healthier gut, better digestion, and improved immunity.

But are probiotics really helping horses as much as we believe?
And more importantly, do they even remain alive long enough to work?

This article breaks down the current scientific evidence, what’s real versus marketing hype, and what your horse truly needs for a resilient gut.

What Are Probiotics Supposed to Do?

Probiotics are intended to:

• Aid digestion

• Support hindgut microbial balance

• Reduce inflammation

• Improve stool quality

• Help horses adapt to stress or dietary change

These goals sound ideal, but the actual research shows a much more nuanced picture. Some ingredients help, others do very little, and many products on the market overpromise and underdeliver.

Do Equine Probiotics Actually Work?

Some probiotic-type ingredients do have measurable benefits in horses, but the effectiveness varies dramatically by strain, stability, and how the product is manufactured and stored.

Here is what the research supports.

Tier 1: Most Proven Probiotic Ingredients for Horses

These ingredients have the strongest, most consistent evidence of benefit in equine digestive health.

Bacillus Spores

Examples include Bacillus coagulans and Bacillus subtilis.
These organisms are exceptionally stable, surviving pelleting, heat, oxygen, and long-term storage. Research shows they support hindgut pH, microbial balance, and recovery after exercise-induced inflammation.

Yeast Cultures (Saccharomyces cerevisiae)

Both live yeast and yeast fermentation products have demonstrated positive effects on fiber digestion, hindgut pH, and digestive stability during stress, travel, or diet changes. Yeast is one of the best-supported gut-health ingredients in horses.

Aspergillus oryzae and Aspergillus niger Fermentation Extracts

These are not live probiotics but postbiotic fermentation extracts. They enhance fiber breakdown, improve fermentation efficiency, and help stabilize hindgut conditions. Equine research supports their role in improving digestive performance.

Tier 2: Possibly Helpful, but Evidence Is Mixed or Emerging

These strains show potential under specific circumstances but are not consistently beneficial across studies.

Lactobacillus Strains

For example, Lactobacillus acidophilus.
These may modulate inflammation in controlled research models, but they are extremely fragile, rarely surviving pelleting or barn storage. They do not colonize the equine hindgut.

Bifidobacterium Strains

Including Bifidobacterium longum and Bifidobacterium thermophilum.
These strains show some support during antibiotic use or high-starch challenges but are highly sensitive to heat and oxygen. Their benefits disappear quickly.

Enterococcus faecium

This strain has shown the ability to shift fermentation patterns during dysbiosis in laboratory models. Real-world viability in feed products is low, making benefits inconsistent.

Tier 3: Least Proven for Horses

Multi-Strain “Kitchen Sink” Blends

Products with long lists of probiotic strains often lack equine-specific research and frequently fail independent label accuracy tests.

Human Probiotic Blends for Foals

Controlled studies show no meaningful benefit in preventing or managing diarrhea in foals.

Do Probiotics Colonize the Equine Gut?

No.
Just as in humans, equine probiotics function as temporary visitors rather than permanent residents. They:

• Do not colonize the gut

• Do not alter the microbiome long-term

• Provide benefits only while being fed

• Disappear within days after supplementation ends

This means daily supplementation is required and highlights why stability matters more than the number of strains included.

Do Dead Probiotics Still Have Any Effect?

Sometimes.
When fragile probiotics die during pelleting or storage, their cell-wall fragments and metabolites may still offer mild postbiotic benefits, such as:

• Immune modulation

• Reduced inflammation

• Minor gut-soothing effects

However, dead probiotics cannot:

• Support fiber digestion

• Influence hindgut pH

• Compete with harmful microbes

• Act like active, living probiotics

Only stable strains, such as Bacillus spores and yeast products, retain their functionality under typical feed manufacturing conditions.

Are Most Store-Bought Equine Probiotics Already Dead?

In many cases, yes.

Most lactic-acid bacteria used in horse supplements die quickly when exposed to:

• Oxygen

• Heat

• Light

• Humidity

• Long-term storage

• Pelleting temperatures

By the time these products reach:

• A feed store

• A warehouse

• A barn shelf

• A hot tack trunk

…their probiotic content is often much lower than the label claims.

In contrast, yeast cultures and Bacillus spores are far more stable and survive real-world storage conditions much better.

Many marketing claims in the equine probiotic space rely on strains that simply cannot remain viable across the supply chain from manufacturing to the barn.

What Conditions Do Probiotics Need to Stay Alive?

Most probiotics require:

• Refrigeration or temperatures below 70°F

• Protection from oxygen and humidity

• Darkness

• Airtight, sealed packaging

• A stable, low-moisture environment

These conditions are the opposite of what exists in most barns.
Feed rooms are notoriously hot in summer, uninsulated, and often humid, making survival unlikely for fragile strains.

How Much Effect Do Probiotics Really Have on Horses?

Best evidence of benefit

• Yeast cultures for hindgut stability

• Bacillus spores for reducing inflammation and supporting microbial balance

• Supplemental support during dietary changes, travel, competition, or training

Minimal evidence

• Lactic-acid bacteria for general digestive support

• Prevention of colic

• Long-term microbiome modification

• Treatment of diarrhea in otherwise healthy horses

No evidence

• Permanent colonization of the gut

• Structural, long-lasting microbiome restructuring

A Transparent Look at the Probiotic Ingredients in Wild Fed

Wild Fed includes a blend of probiotic and fermentation-based ingredients that support the equine digestive system in different ways. Some ingredients provide direct, active support, while others offer enzymatic or postbiotic benefits.

We believe in being fully transparent about what each strain does — and which strains may not survive steam pelleting.

Ingredients With the Strongest Real-World Benefits

Yeast Culture (Saccharomyces cerevisiae)

• Supports hindgut pH

• Improves fiber digestion

• Helps stabilize the microbial environment

• Survives pelleting
  This is one of the most effective gut-support ingredients in the formula.

Bacillus subtilis (Dried Bacillus subtilis Fermentation Product)

• Spore-forming and extremely heat-stable

• Survives pelleting and storage

• Supports hindgut microbial balance

• Helps buffer changes in diet
  This is a reliable, active probiotic in Wild Fed.

Aspergillus oryzae Fermentation Extract

A postbiotic enzyme complex that:

• Enhances fiber breakdown

• Supports healthy fermentation

• Is well supported by equine digestive studies

Aspergillus niger Fermentation Extract

Another postbiotic ingredient that:

• Provides digestive enzymes

• Supports nutrient absorption

• Contributes to overall digestive efficiency

Ingredients With Some Benefit, but Likely Not Alive After Pelleting

Because Wild Fed is steam-pelleted, the following strains are unlikely to remain viable in the final product. They still contribute mild postbiotic benefits, but not the full effects of active probiotics.

• Lactobacillus acidophilus

• Enterococcus faecium

• Bifidobacterium longum

• Bifidobacterium thermophilum

These ingredients may provide subtle immune-supportive or gut-calming effects through their structural components, but they are not the primary drivers of digestive support in the formula.

Final Takeaway

Horses do benefit from certain probiotic-type ingredients — but only from the right ones. Stability, strain selection, and manufacturing conditions matter far more than the number of strains listed on a label.

In Wild Fed, the most meaningful digestive support comes from:

• Saccharomyces cerevisiae

• Bacillus subtilis

• Aspergillus oryzae

• Aspergillus niger

These ingredients are stable, evidence-based, and effective under real-world conditions.

Fragile strains, such as Lactobacillus and Bifidobacterium species, may not survive pelleting, but they still offer mild post-biotic effects and contribute to the overall digestive profile.

As research evolves, Wild Fed continues to evolve with it — committed to honesty, clarity, and the highest standards in equine nutrition.