Probiotics For Horses | BioStar US

How to Select the Best Probiotics for Horses

Probiotics for horses are popular supplements in the equine world. They are often included in commercial feeds, multivitamin and mineral formulas, as well as digestive supplements for horses.

Each horse has its own unique microbiome, depending on genetics, diet, and stressors. Knowing which probiotic to use and when to use it helps address your horse’s particular needs, which leads to a healthier and happier horse.

BioStar offers BioFlora EQ, Bio Yeast EQ, and Sym-Biota EQ to provide high-CFU, live microorgansim cultures that can grow and thrive in the GI tract where supportive beneficial microflora growth is needed the most:

BioFlora EQ is a cooling supplement providing multiple strains of microorganisms plus mannan oligosaccharide (MOS), and is microencapsulated for delivery to the small intestine and hindgut.

Bio Yeast EQ is a warming supplement providing two strains of live yeast. It’s also microencapsulated to ensure delivery to the hindgut.

Sym-Biota EQ is a neutral soil-based supplement with special probiotic support for the intestinal tight junctions and the immune system.

Below, we will highlight why probiotics for horses are important and how to select the best one for your horse.

Probiotics for Horses

Address your horse’s unique needs with either a warming or cooling probiotic.

What are probiotics?

Probiotics are beneficial bacteria strains that live in the GI tract.  These microorganisms exist along with the pathogenic bacteria (or “unfriendly” bacteria) which are known to cause infection and GI tract upset.

In a healthy GI tract there are more colonies of beneficial bacteria than pathogenic bacteria.

In horses there are thousands of microbial species; the strains used in probiotic supplements and feeds represent a small minority of the colonies that exist in the GI tract.  Microbial diversity is essential to GI tract health.

Examples of beneficial bacteria

The most common beneficial microorganisms used in probiotic supplements and feeds for horses are:

  • Lactobacillus 

  • Enterococcus 

  • Bifidus

  • Saccharomyces cerevisiae 

  • Saccharomyces boulardii 

  • Aspergillus oryzae 

The last three microorganisms listed above are common yeast strains.

All probiotics for horses are not alike

Yeast probiotics for horses work predominantly in the hindgut, helping in the fermentation of fiber from hay and forage.

Most milk-derived probiotics for horses — Lactobacillus, Enterococcus and Bifidus — work predominantly in the small intestine, while some specific strains work in the respiratory tract.  Several Lactobacillus strains are also present in the stomach.

Soil-based probiotics, Bacillus strains, are found in healthy soils. Horses are exposed to these beneficial bacteria when they eat grass, and roll in the dirt. Bacillus strains are hardy, and can survive passage through the stomach to the small intestine and colon.

Live or viable probiotics for horses are labeled with CFUs (colony-forming units), just like yogurt and kefir. Live probiotics are capable of colonization.

Probiotic strains in supplements and feeds that are not labeled with CFUs are not providing live or viable beneficial bacteria.

For example: “Yeast culture probiotics,” commonly found in commercial feeds and some supplements, are not live and therefore not capable of colonization in the GI tract.

This doesn’t mean that there are no benefits. Probiotics that are not live can still work as prebiotics in the GI tract, because they serve as food for the live, beneficial microorganisms that have already formed colonies there.

How to evaluate probiotic potency

The amount of CFUs in a probiotic supplement is important because the gastrointestinal system comprises tens of trillions of microorganisms.

A label that states “100 million CFUs” sounds impressive, but compared to the trillions in the gut, will not be enough to work on a therapeutic level.

A live probiotic capable of colonization should supply at least 100 billion CFUs. That’s a minimum requirement; some researchers point to the need for 400 billion CFUs in cases where acute probiotic support is needed.

Bottom line: Probiotics for horses should provide at least 100 billion CFUs per serving.

Many probiotic supplements never get past the stomach

The acids in a horse’s stomach can corrode metal, so imagine what stomach acids do to probiotic strains given orally.

When choosing probiotics for horses, look for strains that are given an enteric coating or are “microencapsulated”. This means they are protected from stomach acids; they can move through the stomach safely, where they can then work in the small intestine and hindgut.

The Bacillus strains are one of the few strains that do not need microencapsulation.

Health benefits of probiotics for horses

Probiotics help in multiple ways. Live probiotic supplements can:

Probiotics for Horses

Probiotics help restore microbial balance to the GI tract after antibiotic therapy.

Probiotics from an Eastern medicine perspective

In Ayurvedic medicine, all foods and plants are classified into three categories: warming, cooling, and neutral.

Milk, for example, is a cooling food. This means that probiotic strains from milk (Lactobacillus, Bifidus, and Enterococcus) are cooling to the digestive tract.

If you have a horse with gastric or hindgut ulcers, and therefore heat in the GI tract, you need cooling probiotics.

Yeast is a warming food. Yeast probiotics help to increase digestive fire.

Horses that need to gain weight, or are older and may not be utilizing all the feed and forage you are providing, or have hard stools will need a warming probiotic, and that would be yeast.

Bacillus strains are neutral soil-based microorganisms.  These strains will not cool or warm the GI tract.  This is especially important for maintaining homeostasis.

Is it okay to mix both cooling and warming probiotics for horses?

Many supplement companies combine the cooling probiotic strains from milk with the warming probiotic strains from yeast. The theory is to provide the milk-derived probiotics that live primarily in the small intestine, along with yeast probiotics for the hindgut.

However, from an Eastern medicine viewpoint, mixing cooling with heating can adversely affect digestion, including the absorption, assimilation, and production of digestive enzymes.

This is why, in Ayurvedic medicine, milk is considered incompatible with yeast.  So blending milk-derived probiotics with yeast probiotics would not be recommended.

Four important prebiotics for your horse

Prebiotics are food for the bacteria in the gut.  They support the existing colonies of microorganisms for overall intestinal health.

Among the most noted prebiotics in horse supplements and feed are inulin, fructo-oligosaccharides (FOS), beta-glucans, and mannan-oligosaccharides (MOS).

FOS and inulin prebiotics

FOS and inulin are capable of feeding friendly microorganisms in the gut as well as, unfortunately, the not-so-friendly opportunistic and pathogenic bacteria like Candida and Salmonella.

If there is already an imbalance in the GI tract that favors opportunistic bacteria, FOS in particular can actually help these organisms grow.

Beta-glucan prebiotics

Beta-glucans from barley, oats, yeast, and mushrooms are capable of reaching the hindgut where they are fermented and provide food for the beneficial microorganisms in the colon.

Beta-glucans are also beneficial because they slow the transit time of starches, and support more efficient nutrient absorption.

best Probiotics Horses

Beta glucans from mushrooms are capable of reaching the hindgut where they are fermented, providing beneficial prebiotics to your horse’s microbiome.

MOS prebiotics

Mannan oligosaccharides (MOS) are especially important for horses with hindgut ulcers.

Ulcers in the hindgut are the result of a change in the pH.  This is often due to starches not being fully digested in the small intestine, and ending up in the hindgut. Since hindgut bacteria do not digest starches, they die off and the pathogenic bacteria increase.

MOS helps regulate the pH of the hindgut so that pathogenic bacteria cannot flourish there.  MOS prebiotics can also bind to pathogenic bacteria and help flush them out of the body.

How to determine the right probiotics for your horse

Common examples of when to use a cooling probiotic versus a warming probiotic:

Look for a COOLING probiotic if:

  • your horse has undergone antibiotic therapy
  • your horse has gastric or hindgut ulcers
  • your horse is under stress, particularly in summer months.
  • your horse has diarrhea. In cases of longterm diarrhea add a smectite or bentonite clay to help soak up the toxins.
  • your horse is running a temperature.

Look for a WARMING probiotic if:

  • your horse is underweight.
  • your horse is a hard keeper.
  • your horse is a senior who needs digestive support.
  • your horse has hard, dry stools.

IF your horse needs both a cooling and a warming probiotic, do not give them at the same time.  Try to space out the cooling from the warming by 6 to 8 hours.

Look for a NEUTRAL probiotic if:

  • your horse struggles with IBS.
  • your horse has limited exposure to fresh grass.
  • your horse needs non-specific probiotic support.

Senior horses may benefit from a warming probiotic for additional digestive support.

Probiotics are important for horse health

Probiotics for horses are important for the health of the GI tract and provide necessary immune support for wellness.

Choosing a probiotic supplement can seem like a daunting task, so always ask yourself:

“Does my horse need to cool the fire in the GI tract
or increase the fire in the GI tract, or neither?”

This will help you focus on the best bacterial strains to support your horse.

Select the probiotic supplement that’s right for your horse

BioFlora EQ is a cooling supplement with 100 billion CFU’s of beneficial live colonizing microorganisms plus MOS. It is microencapsulated to ensure delivery to the small intestine and hindgut.

BioFlora EQ | BioStar US

When to use BioFlora EQ:

  • After antibiotic therapy
  • For horses with gastric or hindgut ulcers
  • For horses with diarrhea
  • For a horse with a fever
  • For horses under stress
  • You need to cool your horse’s intestinal fire

Bio Yeast EQ is a warming supplement with two strains of live yeast, providing 100 Billion CFU’s; and it’s microencapsulated to ensure delivery to the hindgut.

Bio Yeast EQ | BioStar US

When to use Bio Yeast EQ:

  • If your horse needs to gain weight
  • If your horse is a hard keeper
  • For a senior horse who needs digestive support
  • If your horse has hard, dry stools
  • If you need to increase the digestive fire in the GI tract

Sym-Biota EQ is a neutral supplement with three strains of probiotics plus fulvic and humic acids, and chaga mushrooms.

Sym-Biota EQ | BioStar US

When to use Sym-Biota EQ:

  • If your horse spends less than 5-6 hours a day on pasture
  • If your horse is on a dry lot
  • If you horse has IBS
  • If your horse has excessive exposure to Glyphosate
  • If your horse needs probiotic support that does not increase fire in the GI tract or decrease fire in the GI tract
  • If your horse has immune system challenges

Each horse has its own unique microbiome, depending on genetics, diet, and stressors. Knowing which probiotic to use and when helps to address your horse’s particular needs and leads to a healthier and happier horse.


Tigger Montague | BioStar US About the Author: With over 30 years experience in the equine and human supplement industry, Tigger Montague knows nutrition from the synthetic side as well as the whole food side. She started BioStar US in 2006 with formulas she created in her kitchen.  Before she started the company, she was an avid rider and competitor with eventing and show jumping, until she got hooked on dressage in the late 1980’s.  She has competed on horses she’s owned and trained all the way from training level to Grand Prix.


Jergler D. “The Pros and Cons of Equine Probiotics.” Veterinary Practice News. June 2014.

Larson E. “Study Evaluates Effects of Probiotics for Horses.” April 2013.

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