Maintaining your horse’s digestive health is integral to maintaining their overall health.

Digestive issues such as colic, ulcers, and hindgut acidosis are some of the most commonly diagnosed health conditions in horses.

Furthermore, without a healthy gut, horses could experience secondary nutrient deficiencies, impaired energy metabolism, lower feed efficiency, and could be at higher risk of pathogenic diseases.

Unsurprisingly, nutrition is a major component of optimizing your horse’s stomach and hindgut health. How and what you feed your horse can help to maintain a healthy gut environment and support the microbiome.

Looking for the best digestive health supplements for your horse? Several nutritional supplements have been investigated in horses and have demonstrated efficacy for maintaining a healthy gut.

In this article, we will review the scientific data behind fifteen popular ingredients used to support digestion and gut function in horses.

We will discuss the potential benefits of these supplements and their efficacy according to the available research and clinical trials.

Overview of Equine Digestive Health

The digestive system of the horse is unique compared to other mammals. Horses are non-ruminant herbivores, meaning they naturally only eat plants and have a single-compartment stomach.

The stomach and small intestine of the horse function similarly to that of humans. The hindgut consists of the cecum and colon, in which the cecum and large colon are similar to the rumen in cattle and other ruminants.

Horses are also hindgut fermenters. This means that they rely heavily on fermentation processes in the hindgut to derive energy from the forage they consume.

Microbes in the hindgut are responsible for fermentation of cellulose and other plant fibres to produce volatile fatty acids (VFAs). These fatty acids then get absorbed in the cecum and large intestine and used for energy, supplying approximately 40% of the horse’s caloric energy.

Horse Digestive Tract - Hindgut & Foregut

Steps of Digestion in Horses

Digestion of food involves the following steps in horses: [1]

1) Mechanical Digestion (Chewing)

The breakdown of food starts with chewing or mastication in the mouth. While often overlooked, chewing is important because it breaks food down into smaller pieces.

This increases the surface area of the feed for digestive enzymes to further break down these particles.

Saliva is also produced when chewing, which promotes gastric health by acting as an acid buffer in the stomach.

Horses that have dental issues or missing teeth will often need to be on a modified diet because they cannot chew their food well.

2) Chemical Digestion (The Stomach)

Food enters the stomach and is further broken down by digestive enzymes, microbes, and gastric acid.

The naturally acidic environment of the stomach plays a key role in the immune system. It can prevent infectious or harmful microorganisms from entering the rest of the digestive system.

The predominant stomach acid is hydrochloric acid and horses can produce 16 gallons per day of this acid.

It is continuously produced by stomach cells even when there is no food present in the stomach, which, incidentally, is why horses with intermittent feeding schedules are at higher risk of ulcers.

3) Nutrient Absorption (The Small Intestine)

When food leaves the stomach, it enters the small intestine. Enzymes continue to break down the food even more.

Importantly, the small intestine is the major location for the absorption of nutrients from starches, proteins and fat in the diet.

4) Hindgut Fermentation (Cecum and Colon)

The vast microbial population in the hindgut is primarily responsible for breaking down fibre from hay, pasture and other forages.

This produces large amounts of volatile fatty acids (VFA), which are the major energy source for the horse.

Leftover, or undigested, food moves through the rest of the colon where water is absorbed and feces is formed and excreted.

Mad About Horses
Join Dr. Chris Mortensen, PhD on an exciting adventure into the story of the horse and learn how we can make the world a better place for all equines.
Apple Podcasts Spotify Youtube
Mad Barn - Equine Nutrition Consultants

How to Support your Horse’s Digestive System

Horses are known for having particularly sensitive digestive systems. They are very susceptible to digestive upsets, particularly when anything in their diet or routine changes.

If you are reading this article, your horse is likely experiencing one of the following complaints which can be linked to gut health:

Horses with any of these digestive complaints can benefit from dietary supplements. Improving your horse’s gut health can not only impact digestion and nutrient absorption but also immune function, performance, comfort and overall well-being. [19]

Additional benefits of a well-functioning digestive system include:

  • Improved synthesis of vitamins and key nutrients
  • Improved pathogen resistance
  • Protection against toxins
  • Better gut-barrier function
  • Influencing the gut-brain connection to promote positive behaviour and mood
  • Improved body condition
  • Increased resistance to stress

Before adding supplements to your horse’s feeding program, we recommend consulting with an equine nutritionists. You can submit your horse’s diet for analysis online and our nutritionists can provide a complimentary review.

Top 15 Supplements for Your Horse’s Digestive Health

1) Visceral+

Visceral+ is Mad Barn’s gold-standard digestive health supplement. It is designed to support gastric and hindgut health and immune function.


5 stars
4 stars
3 stars
2 stars
1 star

Learn More

  • Our best-selling supplement
  • Maintain stomach & hindgut health
  • Supports the immune system
  • 100% safe & natural


  • Bio-Mos™
  • Yea-Sacc1026™ – Saccharomyces cerevisiae yeast
  • 20 billion CFUs of probiotics
  • Lecithin
  • Docosahexaenoic Acid (DHA) – an omega-3 fatty acid
  • Methionine
  • Kelp meal
  • Magnesium
  • Choline
  • Marshmallow Root Extract
  • Meadowsweet
  • Slippery Elm Bark
  • Glutamine

Targets for Digestive Health

Visceral+ supports the stomach, hindgut and immune system.

2) Optimum Digestive Health

For horses with hindgut issues or horses that need help keeping weight on, Optimum Digestive Health is the recommended choice.

Optimum Digestive Health

5 stars
4 stars
3 stars
2 stars
1 star

Learn More

  • Prebiotics, probiotics & enzymes
  • Support hindgut development
  • Combats harmful toxins in feed
  • Complete GI tract coverage


  • Digestive Enzymes to help break down feed components in the small intestine
  • Saccharomyces cerevisiae species of yeast which has been clinically shown to promote digestive health in a variety of animals
  • Kelp meal for its rich amino acid, vitamin, and mineral profiles
  • Dietary Escape Microbial Proteins as a high-quality protein source that will be digested in the small intestine
  • Prebiotics such as beta-glucans which feed the beneficial microbes along the digestive tract
  • Mannan oligosaccharides which bind to and neutralize toxins that may be present in feed
  • Magnesium, sodium, and potassium which are important electrolytes that support gut motility
  • Peppermint for its soothing effects on the digestive system
  • Mad Barn’s 5-Strain Probiotic to balance the gut microflora and support fibre digestion in the hindgut

Targets for Digestive Health

Optiumum Digestive Health supports hindgut health and immune function.

3) Yeast

Yeast is a type of fungus that is commonly used as a probiotic to support hindgut function in horses.

While there are many different species of yeast, [5] Saccharomyces cerevisiae is most commonly used in horses.

Yeast cultures can promote nutrient absorption from the diet and improve feed efficiency. They are commonly fed to horses that are hard keepers, senior horses and performance horses with greater nutrient demands.

Yeast may also support immune function. The cell walls of yeast are used as toxin binders in equine supplements.

Saccharomyces cerevisiae yeast support hindgut fermentation of fibre and enhance nutrient absorption. Yeast may also support immune function.

Targets for Digestive Health

  • Fibre fermentation by the hindgut microbiome
  • Immune response

Efficacy of Yeast for Digestive Health

Research has demonstrated that live yeast cultures in equine diets survive passage through the acidic stomach and reach the hindgut intact. [5]

Fibre Digestion

Yeast supplements can support fibre digestion in the hindgut, which supplies critical nutrients and caloric energy to your horse.

High-starch diets are one of the main culprits for impaired fibre digestion and hindgut dysfunction in horses.

When horses are fed excess grain, high levels of starch reach the hindgut where microbes convert it to lactic acid.

This lowers the pH (increases the acidity) of the hindgut which negatively affects fibre digesting microbes, potentially leading to dysbiosis.

In one study, the negative effects of a high-starch diet were mitigated by adding yeast to the diet. [6]

Horses in training on high-starch diets had improved fibre digestibility when yeast was included in the diet. [2] This improved overall digestible energy in the diet and could support athletic performance. [12]

Yeast may also benefit horses given low-quality hay by helping them extract more energy and nutrients from the feed. Horses fed low-quality hay and supplemented with yeast showed greater fibre digestibility compared to horses fed low-quality hay without a yeast supplement. [3]

Protein Digestion

Yeast has been shown to increase the nutritional value of low-quality hay by improving protein digestibility. [3]

Yearlings fed live yeast cultures also had increased microbial production of amino acids. [4]

It’s unclear whether these amino acids can be absorbed from the hindgut. However, they can be consumed by other microbes to support hindgut digestive function.

This can also reduce nitrogen excretion in urine to decrease the environmental footprint of horses.

Digestive Dysfunction

Horses with digestive issues such as colitis may benefit from yeast supplements.

Researchers fed horses diagnosed with acute colitis a yeast supplement at either 25 g or 50 g for ten days. At the end of the study, horses in both groups showed decreased severity of colitis and a shorter duration of gastrointestinal disease. [7]

Yeast has been shown to benefit immune function in other species. In pigs, yeast appears to support the immune system and overall health by improving gut barrier function. This prevents bacteria and other pathogens from entering the body. [8]

In a recent review study, yeast was found to improve immune function in livestock through a variety of mechanisms. [9] More research is needed to understand how yeast influence the immune system in horses.

You can read more about the known benefits of yeast in horses in our article: 7 Research-Backed Benefits of Yeast for Horses.

THE VERDICT: Significant evidence of efficacy for improved nutrient digestibility in the hindgut of horses. More research is required for immune-modulating effects.


4) Digestive Enzymes

Digestive enzymes are involved in enzymatic digestion of nutrients in the gut. Different enzymes break down different dietary components into fractions that can be absorbed.

These chemicals are naturally present in saliva, the stomach, the small intestine and produced by microbes in the hindgut.

Popular digestive enzyme supplements for horses can include one or more of the following enzymes:

  • Amylase: Digestion of starch into glucose and maltose
  • Protease: Breaks down proteins into amino acids, or smaller peptides
  • Lipase: Involved in the breakdown of fats
  • Phytase: Breaks down phytate to make phosphorus available for absorption
  • Cellulase: Breaks down cellulose – a fibre component of plant cell walls
  • Xylanase: Digestion of hemicellulose – a fibre component of plant cell walls

Mad Barn’s Optimum Digestive Health contains Allzyme SSF, a proprietary formulation of digestive enzymes. This blend is commonly used in livestock to support nutrient digestion and absorption in the intestines.

Digestive enzymes can promote digestion of food to support nutrient absorption. They may have a role in promoting digestive health in horses.

Targets for Digestive Health

  • Increase digestion and breakdown of food to enhance nutrient absorption
  • Support hindgut fibre digestion
  • Enhance phosphorus absorption


The efficacy of digestive enzymes varies depending on the type and combination of enzymes used as well as the content of the diet.

In 2003, a study evaluated the effects of xylanase and cellulase on fibre digestion. These are enzymes that microbes in the hindgut produce to break down fibre.

Yearling geldings were fed Bermudagrass hay along with one of four additional feeds: textured sweet feed, pelleted concentrate, whole oats, or alfalfa cubes. Horses received either the supplemental xylanase and cellulase or no digestive enzymes for 7 days. [13]

The researchers observed improvements in fibre digestion when enzymes were added to the sweet feed and whole oat diets but not in other diets.

It should be noted that another study found no improvements in fibre digestibility when cellulase was given to horses fed grass hay with whole oats. [14] More research is required to understand the variability in results.

Effects on the Microbiome

Digestive enzyme supplementation may impact microbial function in the hindgut.

Researchers at North Carolina State University assessed the effects of multiple digestive enzymes on cell culture of microbes taken from the cecum of horses. [15]

The purpose of this study was to mimic high-carbohydrate diets in which large amounts of starch reach the hindgut.

The researchers hypothesized that adding high levels of lipase, protease, cellulase, and amylase would support fermentation by microbes taken from the hindgut.

The results demonstrated higher production of volatile fatty acids when digestive enzymes were added. This could theoretically lower pH and negatively affect fibre digesting microbes in the hindgut, but the researchers noted that the pH was not low enough to induce acidic stress.

More research on the impact that digestive enzymes could have on the microbiome is warranted.

Mineral Absorption

Digestive enzymes may enhance the absorption of minerals like phosphorus from the gut. Phosphorus is naturally found in plant material bound within phytate making it unavailable for absorption.

Adding phytase to the diet increases phosphorus digestibility and decreases its excretion in feces. This is important for horses with impaired phosphorus digestion such as senior horses, horses that have had previous colic resection surgery, and horses with chronic intestinal damage from a high worm load. [16]

THE VERDICT: Some evidence of improved digestive function in horses. More research is required.

Some Efficacy

5) Kelp Meal

Kelp is a type of seaweed and is often considered a nutritional “superfood”. It is used to improve digestive health in livestock.

It contains a number of valuable nutrients such as essential amino acids, fatty acids, fibre, and many vitamins and minerals. [20]

Kelp is also a source of prebiotic fibre, which can help promote the growth of probiotic bacteria.

Targets for Digestive Health

  • Immune response
  • Anti-inflammatory and antioxidant effects
  • Microbial environment
  • Digestive tract integrity

Kelp meal is a great supplement for horses due to its broad nutrient profile. More research into its direct effects on gut health is warranted.


Kelp meal is a nutritionally dense feed additive for horses. With regards to digestive function, the high-quality protein content and prebiotic components are most relevant.

Amino acids are the building blocks of protein. Kelp meal supplies nine essential amino acids and 11 non-essential amino acids. [20]

Proteins build and repair tissues throughout the body, including in the digestive tract where cells have a high turnover rate. [1]

Cells lining the digestive tract have some of the shortest lifespans of any cells in the body, surviving for 3 days on average.

New cells are constantly developing to replace old cells that die off. This process requires a lot of nutrients – including amino acids – to remodel stem cells into functional cells of the digestive tract.

Supporting cell turnover is especially important when there are digestive issues that damage the intestinal lining.

Horses experiencing irritable bowel syndrome, inflammatory bowel disease, leaky gut, or hindgut ulcers need the right balance of amino acids to support tissue repair.

Prebiotic Effects

Kelp meal is high in polysaccharides which acts as a prebiotic to feed beneficial microbes in the gut and decrease levels of harmful microbes.

Seaweed supplementation was found to decrease E. coli populations in the stomach and intestine of pigs and increase beneficial microbes including Lactobacilli. [21]

More research is needed to study the prebiotic effect of kelp meal in horses.

THE VERDICT: Significant evidence for digestive health in other species. More research is needed in horses.


6) Probiotics

No list of digestive health supplements would be complete without discussing probiotics.

Probiotic supplements contain live microorganisms that are fed orally to the horse for a health-promoting effect. [22] These “good” bacteria support digestion and immune function.

Horse owners often think of the hindgut when discussing the microbiome, but bacteria actually exist throughout the digestive system.

A healthy microbiome requires a delicate balance between so-called good and bad bacteria. Pathogenic bacteria, such as E.coli, are considered “bad” because they produce toxins that kill good bacteria.

Diet, environment, stress, illness, medications, and many other factors can tip the scale towards dysbiosis, or a destabilized microbial environment. Probiotic supplements can help to maintain a healthy microbial balance throughout the digestive tract.

Targets for Digestive Health

  • Nutrient digestibility and absorption
  • Microbial environment
  • Immune response
  • Synthesis of proteins or enzymes
Probiotics play important roles in digestion, nutrient absorption, vitamin synthesis, enzyme production, and immune protection.

Not all probiotic supplements work equally well. There are many species and strains of probiotics to consider, as well as different supplement formulations to preserve the viability of the microbes.

Some of the most researched species of probitoics include:

  • Lactobacillus acidophilus: This bacteria species is known for producing lactic acid
  • Lactobacillus fermentum: Another lactic acid producing bacteria that is found naturally in the horse’s gut
  • Lactobacillus casei: Thought to aid in immune response, L. casei is often supplemented to reduce infections in the intestine and to promote regular bowel movements
  • Lactobacillus plantarum: Also a lactic acid producing bacteria. It may prevent the growth of harmful bacteria by competing with them for the same food sources
  • Enteroccocus faecium: The most prevalent species of probiotic bacteria in horses

Mad Barn’s Optimum Probiotic contains the five strains mentioned above. Each serving provides 20 billion viable CFUs to ensure adequate numbers reach the hindgut.

The Optimum Probiotic 5-strain blend has been scientifically formulated to support your horse’s digestive health. It works to balance the horse’s gut microflora, improve nutrient assimilation and support the immune system.

Optimum Probiotic

5 stars
4 stars
3 stars
2 stars
1 star

Learn More

  • 20 billion CFUs per serving
  • Pure probiotic with no fillers
  • Blend of 5 beneficial strains
  • Only $10 for 1 month

Efficacy of Probiotics for Digestive Health

Probiotics may exert an anti-inflammatory effect on the digestive tract. In cell culture studies, probiotics have been shown to inhibit certain inflammatory mediators. [22]

Probiotic have also been shown to improve mucous integrity and immunity in multiple cell culture studies. [22]

Different species of probiotic bacteria produce lactic acid, fatty acids, acetic acid, and butyric acid. These compounds maintain a healthy pH throughout the gut and may prevent the growth of harmful bacteria, such as Clostridium.

In one study using cell cultures, the addition of L. fermentum did not inhibit Clostridium growth. But it did prevent the Clostridium bacteria from producing harmful toxins. [23]

In another study, researchers used an in vitro design to mimic the fermentation process of the gut. Using fecal samples from Azteca horses, they investigated the effects of a probiotic supplement containing Lactobacillus strains on fibre digestion. [24]

The researchers found that the probiotic resulted in a slightly lower pH and higher metabolizable energy, demonstrating increased fibre digestion. Higher dosages of probiotics were correlated with greater fibre digestion. [24]

In vitro studies are important for informing our understanding of how supplements such as probiotics work. However, clinical trials in horses are required to validate efficacy.

Clinical Trials

Clinical trials investigating the supplementation of probiotics in horses are difficult to compare. Doses and probiotic strains differ between studies. The duration of supplementation also varies significantly.

One study in foals investigated supplementation with a blend of Lactobacillus strains. The researchers found that foals supplemented with the probiotic had less diarrhea. [25]

Another study in horses hospitalized for colic did not find any differences in diarrhea incidence or shedding of Salmonella for horses supplemented with Lactobacillus. [26]

Read more about the benefits of probiotics for horses in our article: 6 Science-Backed Benefits of Probiotics for Horses.

THE VERDICT: Some evidence of efficacy in horses. However, evidence varies across different probiotic strains and blends. More research is required.

Some Efficacy

7) Spirulina

Spirulina is a type of blue-green algae that grows in fresh water lakes.

Athrospira platensis and Athrospira maxima are the two species commonly used in dietary supplements. They are rich in proteins, essential fatty acids, vitamins, and minerals.

Spirulina is associated with improved immune function, anti-inflammatory effect, and antioxidant protection.

Targets for Digestive Health

  • Immune response
  • Anti-inflammatory and antioxidant
  • Nutrient digestibility
  • Microbial environment


5 stars
4 stars
3 stars
2 stars
1 star

Learn More

  • Supports immune function
  • Used in horses with allergies
  • Supports metabolic health
  • Rich in vitamins & protein


Spirulina modulates many immune response pathways in the body. It may support immune functions specific to the digestive tract.

Inflammation in the gut weakens the intestinal barrier, resulting in the development of a leaky gut. This can allow bacterial products to enter the bloodstream from the gut.

The ensuing immune response is a contributing factor for laminitis, particularly in horses with equine metabolic syndrome (EMS).

In an in vitro study, intestinal cells were taken from horses diagnosed with EMS and treated with Spirulina. The researchers found that Spirulina reduced inflammation and oxidative stress in intestinal cells. [10]

EMS horses fed spirulina also had improved insulin sensitivity and weight loss.

In another study, healthy horses were fed 500 g of feed containing Spirulina daily for three months. These horses had lower fasting insulin levels and improved glucose tolerance. [10]

The anti-inflammatory and antioxidant benefits of Spirulina have been shown in cells isolated from the intestine of horses. However, more research in horses is required to assess the effects of feeding spirulina on digestive function.

Gastric Mucosa and Microbiome

Spirulina may also support the gastric mucosa and help maintain the structural integrity of the gastrointestinal tract.

A healthy mucous lining can prevent intestinal damage from bacteria and pathogens, and reduce the risk of ulcers.

This could have benefits for nutrient absorption, as demonstrated in pigs. Spirulina supplementation in swine was found to improve digestive tract structure and function. [11]

In other animals, it has been shown to confer benefits on the gut microbiome, but this has not been directly studied in horses. [17][18]

Spirulina is safe for equine consumption and exhibits anti-inflammatory effects in conditions ranging from EMS to recurrent respiratory issues such as allergies, heaves and inflammatory airway disease.

Read more about the top 9 Research-Backed Benefits of Spirulina for Horses here.

THE VERDICT: Evidence for digestive health in other species. Some in vitro evidence in horses, but further studies are required.

Some Efficacy

8) Salt and Electrolytes

Feeding plain loose salt to your horse is the cheapest way you can support gut function. Most forage-based diets are deficient in sodium which can contribute to poor appetite, lethargy and poor skin quality.

Feeding your horse adequate salt stimulates thirst and encourages water intake. Proper hydration keeps feed moving through the gut and helps decrease the risk of colic in horses.

We recommend feeding at least two tablespoons (one ounce) of salt per day and ensuring free-choice loose salt and fresh water are consistently available to your horse. This will support gut motility and a healthy digestive tract.


In addition to sodium, your horse requires the following electrolytes in their diet:

  • Potassium
  • Calcium
  • Chloride
  • Magnesium

Sodium, potassium, calcium, and magnesium are cations (positively charged ions), whereas chloride is an anion (negatively charged ion).

Electrolyte requirements are higher in horses that participate in intensive exercise such as endurance races and horses that live in hot climates. The need is also higher in pregnant and lactating mares.

These horses experience a greater loss of electrolytes through sweat, urine, and milk supply. Electrolyte deficiency may result in reduced appetite, lower water intake, muscle weakness, lethargy, and other complications.

Providing adequate electrolytes is important for nerve impulse transmission, energy metabolism, enzyme activity, contractions of muscle tissues, and regulating pH levels.

Targets for Digestive Health

  • Support proper bodily functions
  • Encourage hydration
  • Promote gut motility


Fluid balance is greatly affected by digestive health. Electrolyte imbalances are observed in over 70% of horses with diarrhea due to depletion of water and electrolyte minerals.

This can have further negative consequences on the body, including disrupted muscle function and lethargy. [27]

Replenishing electrolytes lost due to an inflamed digestive tract or diarrhea can help horses regain their appetite and stimulate thirst.

The majority of research on electrolyte supplementation in horses focuses on performance or recovery from endurance training. However, electrolyte balance and proper hydration are important in all horses.

Supplementing with electrolytes can help horses replace the electrolytes lost through sweat and improve muscle glycogen synthesis after endurance training. [28][29]

These benefits may be attributed to increased water intake after electrolyte supplementation. [29]

A complete feeding program should incorporate electrolytes for both digestive and overall health.

THE VERDICT: Potential benefit linked to increased water intake and greater gut motility. More research is required to validate hypothesis.


9) Pectin-Lecithin Complex

Pectin is a type of fibre found in many fruits and vegetables. It is composed of polysaccharides, which are a long chain of sugar molecules.

Lecithin is a phospholipid derived from plants. Phospholipids contain fatty acids used for cell membranes, cell signalling, and many other physiological roles.

The combination of pectin and lecithin can be beneficial for digestive health in horses and can protect against gastric ulcers.

Together, they can protect the stomach lining from damage caused by acids without compromising the overall acidic environment of the stomach.

Targets for Digestive Health

  • Protection against damage from stomach acids and bile
  • Nutrient digestibility
  • Microbial environment


Pectin acts as a prebiotic in the hindgut, supporting the growth of the beneficial microbial population.

Pectin is degraded by microbes to produce volatile fatty acids (energy) which can help maintain a healthy microbiome.

In the stomach, pectin creates a gel that binds to bile acids and protects the stomach lining from acidic degradation.

Lecithin forms a phospholipid layer in the squamous region of the stomach. This layer acts similarly to the protective mucous that is naturally present in the glandular region of the stomach. [30]

Two studies have shown that supplementing horses with a pectin-lecithin complex can aid ulcer healing. [31][32]

THE VERDICT: Suitable evidence of efficacy for digestive health.


10) Peppermint

Peppermint is a perennial flower that has been used throughout human history for its digestive benefits.

In traditional medicine, it is used to soothe digestive upsets, such as cramping, nausea, and diarrhea. Recently, it has been studied for irritable bowel syndrome (IBS) in humans.

Peppermint contains polyphenols and flavonoids known for their antioxidant effects. These active components may also promote the growth of beneficial bacteria for digestive health.

Flavonoids are also known for their anti-inflammatory, antibacterial and anti-viral effects.

Targets for Digestive Health

  • Antioxidant & anti-inflammatory effects
  • Reduces digestive irritations
  • Beneficially alters the microbiome
  • Nutrient digestibility
Peppermint oil is considered safe for horses and is well-tolerated. It has been used throughout history as a digestive tonic.


Peppermint is well-tolerated and has a palatable flavour. [33] It is often added to gut health supplements for horses to support gut comfort.

In broiler chickens, peppermint supplementation (1% in feed) resulted in increased muscle thickness in the digestive tract and improved intestinal morphology. [34]

These results suggest that peppermint may support intestinal structure and function. This could positively affect nutrient absorption and limit the infiltration of harmful bacterial products into the blood.

In a different study, broilers supplemented with peppermint oil (200 or 400 mg/kg diet) exhibited greater protein digestibility. [35]

In humans, peppermint is well-researched for IBS and appears to have antimicrobial and antioxidant effects. [36]

There is limited research available on peppermint’s use in horses. One study in horses supplemented with plant extracts that included peppermint demonstrated antimicrobial properties. [37]

Although there is substantial evidence supporting the digestive benefits of peppermint in other species, there is limited research on horses. While it is likely that peppermint exerts similar effects in horses, more studies will need to confirm this.

THE VERDICT: Evidence for digestive health in other species. Further studies are required in horses.

Some Efficacy

11) Glutamine

Glutamine is an amino acid that serves as a major energy source for cells lining the gastrointestinal tract.

Low levels of glutamine in the diet can impair tissue repair processes and cause atrophy of intestinal tissue leading to poor absorption of nutrients.

Glutamine is commonly added to equine gut health supplements. However, it is often included at low levels that will not have a meaningful impact on digestive health.

Glutamine needs to be supplemented at a high dosage in order to support a beneficial effect.

Targets for Digestive Health

  • Energy source for cells of the GI tract
  • Maintain gut integrity to prevent leaky gut
Glutamine is an amino acid that is used for energy by cells of the GI tract. It supports tissue repair and helps prevent pathogens from entering the body.


Glutamine is a non-essential amino acid, meaning it can be synthesized from other compounds in the horse’s body and does not necessarily need to be provided in the diet. However, there are times in which additional supplementation can be beneficial.

In most mammal species, glutamine is the preferred energy source for intestinal cells. These cells are not able to make glutamine and rely on adequate absorption from the diet and circulating levels in blood to meet their needs. [38][39][40]

The horse’s gut can extract up to 33% of circulating glutamine to use as an energy source. This supports many important processes including building the mucosal barrier to protect cells of the digestive tract from the acidic environment of the gut. [38]

Stress and Immune Response

Cells of the immune system also rely heavily on glutamine as an energy source. Conditions that activate immune cells such as viral infections and stress, can decrease glutamine levels in the blood.

Exercise, stress, and infections have been shown to decrease circulating glutamine in horses. [41] In these situations, cells of the immune system will use up a lot of glutamine which can limit its availability for intestinal tissue.

This is part of the reason why horses in travel and competition are susceptible to digestive upsets including gastric ulcers and diarrhea.

In one study, tissue was taken from the colon of horses and experimentally injured by oxidative stress. Adding glutamine helped minimize the effects of oxidative stress and lower the permeability of the tissue.

By lowering permeability, glutamine decreases the ability for infectious particles to enter the body and trigger an immune response. [42]

Feeding Glutamine

Glutamine is the most abundant amino acid in the bloodstream and much of it is used by the gastrointestinal tract.

Equine dietary supplements that contain glutamine need to provide a significant amount of it in order to have any appreciable effect on gut health. Unfortunately, many products on the market only provide low levels of glutamine.

THE VERDICT: Some evidence of efficacy in horses.

Some Efficacy

12) Aloe Vera

Aloe vera juice and gel are commonly used in horses suspected to have gastric ulcers.

Aloe vera gel derived from the inner leaf of the plant is known for its ability to soothe skin irritations and help heal lesions.

It has traditionally been used to support gastric health and exert a soothing effect on the digestive tract.

Targets for Digestive Health

  • Anti-oxidant and anti-inflammatory effects
  • Barrier protection between the acid and stomach lining
  • Stimulate mucous production
Aloe vera gel is traditionally used to soothe digestive irritation and support tissue repair. Research is limited in horses.


The available research showing benefits of aloe vera for digestive health has been conducted in humans or animal models.

In rats that had gastric ulcers experimentally induced through high-acid intake, adding aloe vera gel to the diet helped decrease inflammation and supported ulcer healing. [51]

This beneficial effect was also observed in rats that had gastric ulcers induced by non-steroidal anti-inflammatory drugs. However, in this case the standard treatment with Omeprazole was more effective than aloe vera for preventing lesions from forming. [52]

To our knowledge, only one study has been done in horses. Researchers in Australia examined the effects of aloe vera gel compared to Omeprazole treatment in horses with gastric lesions.

The horses were given either 17 mg / kg aloe vera gel (equivalent to 8.5 grams for a 500 kg horse) twice per day or the standard treatment of 4 mg / kg Omeprazole.

After 28 days, 56% of the horses given aloe vera gel showed improvement in their ulcer scores but only 17% had totally healed gastric ulcers. In comparisons, 85% of the omeprazole group had improved scores and 75% had healed ulcers. [53]

Therefore, aloe vera gel can support tissue repair in horses with ulcers. But it is not as effective as omeprazole and should not be considered a replacement for therapeutic intervention.

THE VERDICT: Some evidence of efficacy in horses.

Some Efficacy

13) Bentonite Clay and Diatomaceous Earth

Bentonite clay is a popular natural supplement given to horses as a toxin binder. It works by binding to heavy metals and toxins to decrease their absorption and eliminate them from the digestive tract.

Diatomaceous earth is commonly used as a natural dewormer to lower parasite load in the digestive tract.

Although these are popular, they should be used with caution. Bentonite clay can have unintended effects on the uptake of important dietary minerals by binding them and limiting their absorption.

Diatomaceous earth has not been shown to have a significant effect on parasite load.

Targets for Digestive Health

  • Bind and remove toxins from the digestive tract
  • Decrease parasite load
Bentonite clay and diatomaceous earth are thought to benefit digestive health by binding toxins and decreasing parasite load. However the research is limited and does not support widespread use of these compounds for digestive health.


Bentonite clay has an overall positive charge which allows it to bind negatively charged particles.

In several species, bentonite clay has been shown to bind toxins produced by moldy feed.

Aflatoxin is a common mycotoxin found in moldy grains. It can impair liver function and affect the overall health of your horse.

In pigs, adding bentonite clay to an aflatoxin-contaminated diet helped partially restore liver function. However, adding bentonite clay at a level of just 1% of the total diet also decreased magnesium and sodium absorption. [43]

More research is needed on horses. The undesirable effect on mineral availability suggests oral bentonite clay should be reserved for situations of known mycotoxin contamination of feeds and should not be used on an ongoing basis.

Long-term use of bentonite clay might cause secondary mineral deficiencies in the horse.

Diatomaceous Earth

Diatomaceous earth is derived from the fossils of microscopic marine organisms including diatoms, phytoplanktons and algae. It is high in silica which is abrasive and thought to injure parasites in the digestive tract.

Although it is marketed as a natural, chemical-free alternative to common dewormers, its effectiveness is not supported by research. To our knowledge, diatomaceous earth has not been studied in horses.

Since antithelmintic drugs are prohibited in organic farming, several studies have looked at diatomaceous earth as a potential natural alternative for livestock.

Unfortunately, studies have shown no benefit to including this in diets for cattle or sheep. There were no differences in fecal egg count when diatomaceous earth was added and no benefits to growth or other health measures. [44][45][46]

It should be noted that the composition of bentonite clay and diatomaceous earth can vary greatly depending on their source location. Batches of these products can differ from each other and might not be tested sufficiently to know their precise composition.

Although there is some evidence that bentonite clay can bind toxins, it can also impair the absorption of minerals and should be used with caution. The claims that diatomaceous earth can be used as a natural dewormer are not supported by research, although research has not been done on horses.

The Verdict Bentonite clay has potential toxin-binding properties but interferes with mineral absorption. No evidence of efficacy for diatomaceous earth.


14) Activated Charcoal

Activated charcoal refers to a carbonaceous residue that is heated to created pores and typically ground into a fine, black powder.

When ingested as a dietary supplement, these pores help absorb chemicals such as poisonous toxins and prevent their absorption in the gut.

Activated charcoal is commonly used to bind ingested toxins, particularly when a horse might have consumed poisonous plants. It is also thought to be useful for cases of colic and flatulence, although this has not been demonstrated in research studies.

Targets for Digestive Health

  • Bind and remove toxins from the digestive tract
  • Reduce microbial gas production
  • May help horses with colic

Activated charcoal is commonly used to bind toxins and decrease their absorption. The effectiveness of this product has not been reliably shown in horses.


Activated charcoal is a porous compound that can bind other compounds and is thought to have detoxifying benefits.

However, this effect is non-specific. Activated charcoal will not only bind toxins but also to other compounds that are beneficial to the horse.

There is limited research on activated charcoal in horses. One study investigated whether activated charcoal affects gut microbes and the compounds they produce.

Fecal samples were taken and the microbes were given typical feedstuffs along with five different levels of charcoal.

At levels reflective of typical feeding guidelines (30 grams activated charcoal for a 500 kg horse), activated charcoal had no effect on microbial gas production, VFA production or pH level.

This suggests that activated charcoal has no significant effect on microbes in the horse’s hindgut. [47]

Absorption of Toxins

This research did not look at potential effects in the small intestine of horses where ingested toxins would be absorbed. Therefore, more research is required to understand whether activated charcoal has beneficial detoxifying effects in horses.

Research in humans suggests the toxin binding benefit of activated charcoal is limited to a small subset of cases where patients show up in hospital within 2 hours of a drug overdose. Beyond this time, the toxin would be too far along the digestive tract for activated charcoal to have any benefit. [48]

The toxin-binding effect of activated charcoal could be beneficial in horses if it is given immediately after ingestion of a poisonous plant. However, this is likely not the reality in most cases.

Its other purported benefits on colic and flatulence have not been adequately demonstrated by research in horses.

Activated charcoal might have some utility in limited circumstances of suspected ingestion of poisonous plants. More research is needed to support any other perceived benefits.

THE VERDICT: Insufficient evidence to rate efficacy.


15) Antacids

Antacids are used in many species, including humans, to reduce acidity in the gastrointestinal tract.

Antacids commonly used in horses include:

  • Aluminum hydroxide
  • Magnesium hydroxide
  • Calcium hydroxide
  • Dicalcium phosphate

Antacids raise pH levels in the stomach by neutralizing gastric acids.

In horses, gastric ulcers are among the most common ailments associated with impaired digestive health. Ulcers form when acids erode the lining of the stomach.

Raising the pH of the stomach could temporarily reduce the risk of gastric ulceration, but may have a negative overall impact on your horse’s digestive health.

The stomach is acidic for a reason: to activate digestive enzymes, break down food and prevent the spread of pathogenic bacteria.

Targets for Digestive Health

  • Neutralize gastric pH
  • Reduce acidity to allow ulcers to heal


Early studies using an antacid of aluminum hydroxide (8.1 g) and magnesium hydroxide (4.8 g) showed that antacids could raise gastric pH levels in horses.

In 1992, horses were fed this antacid supplement and monitored for six hours post-administration. The gastric pH of these horses increased to greater than 4, but dropped back down before the four-hour mark. [49]

In 1996, a similar antacid supplement containing 30 grams of aluminum hydroxide and 15 grams of magnesium hydroxide was tested in adult horses.

Five horses were fed this antacid and monitored. [50] Gastric pH levels increased to 5 for two hours post-administration.

Multiple studies since then have confirmed that antacids can raise gastric pH levels for a short period of time. This led to widespread use of antacids in horses at risk of ulcers.

Risks of Antacids

However, researchers and equine nutritionists are concerned with the negative effects of antacid use.

The stomach is acidic for a reason. Raising pH levels above 4 may prevent proper functions of the stomach and interfere with the breakdown of food. This could impede normal nutrient absorption.

Additionally, there are concerns with using aluminum-based antacids. High levels of aluminum could negatively impact the digestibility of essential nutrients such as calcium, zinc, and phosphorus.

There is no long-term benefit to providing your horse with antacids. Antacids may provide short-term relief of gastric ulcer irritation but could cause more harm than good.

THE VERDICT: Poor to no long-term benefit for using antacids for digestive health.


Additional Equine Digestive Health Supplements

We have covered many popular equine digestive health supplements in detail above. However, this is not a complete list.

Below are some additional supplements that could benefit your horse’s digestive health based on demonstrated effects in humans or other species.

Factors to Consider when Choosing a Digestive Health Supplement

Digestive health supplements can be a great addition to your horse’s diet. How do you select which one is right for your horse?

Here are some important factors to consider when choosing the best supplement to add to your horses’s feeding program:

  1. Life stage of your horse: The digestive system will change throughout your horses lifespan. Young, growing animals and senior horses are more susceptible to digestive upset.
  2. Workload and training: Horses in heavy work are more likely to experience digestive issues such as gastric ulcers and hindgut acidosis. Competition horses should take preventative measures to reduce the risk of ulcers and dysbiosis.
  3. Digestive health status: If your horse has digestive health issues, such as gastric ulcers or colic, they are at high risk of experiencing recurring issues unless changes are made to their diet and management.
  4. Stress: Environmental conditions that induce stress can have a significant impact on the digestive tract and microbiome. Horses should be adequately acclimated to stressful situations such as trailoring to minimize the effects of stress on digestive function.
  5. Current feeding program: Your horse’s diet is a major contributor to digestive health. A forage-first diet that enables normal foraging behavours is your best defense against most digestive ailments.
  6. Foregut versus Hindgut: Some digestive ailments can be attributed to problems in the foregut (stomach) while other affect the hindgut. Determining which area of your horse’s gut needs more support will help you decide on the right supplement.

Our equine nutritionists are available to answer any questions you may have about different gut health support supplements and your horses’ diet.

Submit your horse’s diet online for a complementary analysis and our nutritionists can give you personalized recommendations.

Is Your Horse's Diet Missing Anything?

Identify gaps in your horse's nutrition program to optimize their well-being.


  1. Ellis, A.D. and Hill, J. Nutritional physiology of the horse. Nottingham University Press. 2005.
  2. Carneiro de Rezende, A.S. et al. Yeast as a feed additive for training horses.. Anim Sci Vet Med. 2012.
  3. Morgan, L.M. et al.Effect of yeast culture supplementation on digestibility of varying forage quality in mature horses.. J Equine Vet Sci. 2007.
  4. Glade, M.J. and Biesik, L.M. Enhanced nitrogen retention in yearling horses supplemented with yeast culture. J Anim Sci. 1986.
  5. Boyle, A.G. et al. Saccharomyces boulardii viability and efficacy in horses with antimicrobial-induced diarrhea.. Vet Record. 2013. View Summary
  6. Medina, B. et al. Effect of a preparation of Saccharomyces cerevisiae on microbial profiles and fermentation patterns in the large intestine of horses fed a high fibre or a high starch diet.. J Anim Sci. 2002.
  7. Desrochers, A.M et al. Efficacy of Saccharomyces boulardii for treatment of horses with acute enterocolitis.. J Am Vet Med Assoc. 2005. View Summary
  8. Zhaxi, Y. et al. A Yeast Probiotic, Improves Intestinal Mucosa Integrity and Immune Function in Weaned Piglets . Sci Report. 2020.
  9. Ganner A. and Schatzmayr, G. Capability of yeast derivatives to adhere enteropathogenic bacteria and to modulate cells of the innate immune system. . App Microbiol Biotech. 2012.
  10. Nawrocka, D. et al. Spirulina platensis Improves Mitochondrial Function Impaired by Elevated Oxidative Stress in Adipose-Derived Mesenchymal Stromal Cells (ASCs) and Intestinal Epithelial Cells (IECs), and Enhances Insulin Sensitivity in Equine Metabolic Syndrome (EMS) Horses. Mar Drugs. 2017.
  11. Furbeyre, H. et al. Effects of dietary supplementation with freshwater microalgae on growth performance, nutrient digestibility and gut health in weaned piglets. Anim 2017.
  12. Glade, M.J. and Campbell-Taylor, M. Effects of dietary yeast culture supplementation during the conditioning period on equine exercise physiology. J Equine Vet Sci. 1990.
  13. Hainze, M.T.M. et al. Fiber digestion in horses fed typical diets with and without exogenous fibrolytic enzymes. J Equine Vet Sci. 2003.
  14. O’Connor-Robinson, C.I. et al. Cellulase Supplementation Does Not Improve the Digestibility of a High-Forage Diet in Horses. J Equine Vet Sci. 2007.
  15. Fellner, V. and Yocum, P.M. Dose Response of an Enzyme Feed Supplement on Equine Cecal Microbial Fermentation. North Carolina State University Animal Science Departmental Report. 2005
  16. Dunnett, C. et al. The effect of a feed ingredient with endogenous phytase activity on phosphorus availability in equine diets. Applied Equine Nutrition and Training. 2009.
  17. Hu, J. et al. Dose Effects of Orally Administered Spirulina Suspension on Colonic Microbiota in Healthy Mice. Front Cell Infect Microbiol. 2019.
  18. Park, J.H. et al. Effect of dietary Spirulina (Arthrospira) platensis on the growth performance, antioxidant enzyme activity, nutrient digestibility, cecal microflora, excreta noxious gas emission, and breast meat quality of broiler chickens.. Poultry Sci. 2018.
  19. Bromiley, M. Natural Methods for Equine Health and Performance . 2nd ed. 2009.
  20. Je Maeher, H.K. et al. Characterization of protein, lipid and mineral contents in common Norwegian seaweeds and evaluation of their potential as food and feed. . Sci Food Agri. 2014.
  21. Dierick, A. et al. Effect of feeding intact brown seaweed Ascophyllum nodosum on some digestive parameters and on iodine content in edible tissues in pigs. J Sci Food Agri. 2009.
  22. Schoster, A. et al. Probiotic Use in Horses – What is the Evidence for Their Clinical Efficacy?. J Vet Intern Med. 2014. View Summary
  23. Allaart, J.G. et al. Effect of Lactobacillus fermentum on beta2 toxin production by Clostridium perfringens . Appl Environ Microbiol. 2011.
  24. Elghandour, M.M.Y. et al. Horse Fecal Methane and Carbon Dioxide Production and Fermentation Kinetics Influenced by Lactobacillus farciminis–Supplemented Diet. J Equine Vet Sci. 2018.
  25. Yuyama, T. et al. Evaluation of a host-specific Lactobacillus probiotic in neonatal foals . Int J Appl Res. 2018.
  26. Kim, L.M. et al. Factors associated with Salmonella shedding among equine colic patients at a veterinary teaching hospital. J Am Vet Med Assoc. 2001. View Summary
  27. Navarro, M. et al. A Comparison of Traditional and Quantitative Analysisof Acid-Base and Electrolyte Imbalances in Horseswith Gastrointestinal Disorders. J Vet Intern Med. 2005.View Summary
  28. Lindinger M.I. and Ecker G.L. Gastric emptying, intestinal absorption of electrolytes and exercise performance in electrolyte?supplemented horses. Exp Physiol, 2012.View Summary
  29. Waller, A.P. et al. Fluid and electrolyte supplementation after prolonged moderate-intensity exercise enhances muscle glycogen resynthesis in Standardbred horses. J Applied Physiol. 2009.
  30. Lichtenberger, L.M. The hydrophobic barrier properties of gastrointestinal mucus. Annu Rev Physiol. 1995.
  31. Ferrucci, F. et al. Treatment of gastric ulceration in 10 standardbred racehorses with a pectin-lecithin complex . Vet Rec. 2003. View Summary
  32. Venner, M. et al. Treatment of gastric lesions in horses with pectin-lecithin complex. Equine Vet J. 2010. View Summary
  33. Goodwin, D. et al. Selection and acceptance of flavours in concentrate diets for stabled horses. Appl Anim Behav Sci. 2005.
  34. Hasan H.I. and M’Sadeq S.A. Effect of peppermint supplementation as powder or extract on broiler performance, serum biochemical content and gut health under E. coli challenge. Iraqi J Agri Sci. 2020.
  35. Emami, N.K. et al. The effect of peppermint essential oil and fructooligosaccharides, as alternatives to virginiamycin, on growth performance, digestibility, gut morphology and immune response of male broilers. Anim Feed Sci Tech. 2012.
  36. Loolaie, M. et al. Peppermint and its functionality: a review . Archives of Clin Microbiol. 2017.
  37. Huerta B. et al. Essential Oils in the Control of Infections by Staphylococcus xylosus in Horses review. J Equine Vet Sci. 2016.
  38. Arteriovenous differences for glutamine in the equine gastrointestinal tract . Am Vet J Res. 1992. View Summary
  39. Harris, R.C. et al. Plasma glutamine concentrations in the horse following feeding and oral glutamine supplementation . Equine Exercise Phys. 2006. View Summary
  40. Souba, W.W. et al. Glutamine metabolism by the intestinal tract. J Parenter Enteral Nutr. 1985.
  41. Routledge, N.B. et al. Plasma glutamine status in the equine at rest, during exercise and following viral challenge. Equine Vet J Suppl. 1999. View Summary
  42. Roetting, A.K. et al. Effects of phenylbutazone, indomethacin, prostaglandin E2, butyrate, and glutamine on restitution of oxidant-injured right dorsal colon of horses in vitro. Am J Vet Res. 2004. View Summary
  43. Schell, T.C. et al. Effects of feeding aflatoxin-contaminated diets with and without clay to weanling and growing pigs on performance, liver function, and mineral metabolism. J Anim Sci. 1993.
  44. Fernandez, M.I. et al. Effect of diatomaceous earth as an anthelmintic treatment on internal parasites and feedlot performance of beef steers. Animal Sci. 2010.
  45. Ahmed, M.A. et al. Studies on the ability of two isolates of Bacillus thuringiensis, an isolate of Clonostachys rosea f. rosea and a diatomaceous earth product to control gastrointestinal nematodes of sheep.Biocontrol Sci and Tech. 2013.
  46. Goertzen, E. Impact of Deworming Treatments on Intestinal Parasite Load in Equines from Middle Tennessee. Middle Tennessee State University. 2014.
  47. Edmunds, J.L. et al. In vitro analysis of the effect of supplementation with
    activated charcoal on the equine hindgut
    . J Equine Sci. 2016. View Summary
  48. Bond, G.R. The role of activated charcoal and gastric emptying in gastrointestinal decontamination: A state-of-the-art review. Annals Emerg Med. 2002.
  49. Murray, M.J. and Grodinsky, C. The effects of famotidine, rantidine and magnesium hydroxide/aluminium hydroxide on gastric fluid pH in adult horses. Equine Vet J Suppl. 1992. View Summary
  50. Clark, C.K. et al. Effect of aluminum hydroxide/magnesium hydroxide antacid and bismuth subsalicylate on gastric pH in horses. J Am Vet Med Assoc. 1996. View Summary
  51. Eamlamnam, C.K. et al. Effects of Aloe vera and sucralfate on gastric microcirculatory changes, cytokine levels and gastric ulcer healing in rats. World J Gastroenterol. 2006.
  52. Borra, S.K. et al. Anti-ulcer effect of Aloe vera in non-steroidal antiinflammatory drug induced peptic ulcers in rats. Afr J Pharm Pharmacol. 2011.
  53. Bush, J. et al. Comparison of aloe vera and omeprazole in the treatment of equine gastric ulcer syndrome. Equine Vet J. 2018. View Summary