Antacid supplements are some of the most popular options for equine gastric ulcer treatment and prevention – but could they be causing more harm than good?
Antacids, such as magnesium hydroxide, are chemical compounds that neutralize stomach acid to temporarily facilitate tissue healing. Excessive acidity in the horse’s gastrointestinal tract can result in ulcers developing as cells of the intestinal wall are eroded away.
Antacids work by counteracting gastric acids, resulting in a higher pH environment in the gut. This buffering effect may result in short-term anti-ulcer benefits. However, because antacids work against the horse’s natural physiology, there is often a rebound effect when a horse stops using them.
In the long run, increasing gastric pH impairs the natural function of the stomach which is to initiate the digestion of feed. This has downstream negative effects throughout the rest of the digestive system.
Long-lasting prevention of gastric ulcers is best achieved by strengthening the barrier function of the intestinal wall and supporting overall gut health.
Simple changes to the horse’s feeding program can have a big impact. These include increasing forage intake and decreasing grain intake as well as providing more frequent, small meals throughout the day.
Avoid equine ulcer supplements that only work to increase gastric pH, either by suppressing acid production or neutralizing stomach acid. Instead, effective supplements for ulcers protect gastric health by supporting the tissues of the stomach lining and maintaining a mucous barrier.
For advice on balancing your horse’s diet to support digestive function and overall well-being, you can submit your horse’s diet for complimentary evaluation by our equine nutritionists.
Understanding Equine Ulcers
They are characterized as open sores or lesions that occur along the lining of the gastrointestinal tract. Ulcers can occur anywhere along the gastrointestinal tract, but most commonly in the stomach. 
The stomach is divided into two compartments: the squamous (or non-glandular) region and the glandular region. The tissues of the stomach are constantly exposed to acids which are used to break down foods and enable nutrient absorption.
Ulcers in the squamous region are the most common ulcers in horses. Ulcers can also occur in the hindgut and glandular region, but each of these different cites of ulceration are associated with different causes.
Horses have naturally evolved to constantly produce acids in the stomach, whether there is food to break down or not. This phenomenon is not a cause for concern in the wild, as non-domesticated horses will spend up to 18 hours a day grazing.
However, when horses are not able to graze throughout the day, the stomach sits empty for long periods of time but still produces acids.
In the glandular region, horses have a natural layer of protection that separates the intestinal lining from harsh stomach acids. This area produces mucous and bicarbonatewhich forms a protective barrier.
The squamous region of the stomach does not have the same defence mechanism because this region does not produce mucous.
Food, water and saliva buffer the stomach acids. This means that when your horse eats or drinks water, some of the acid in the stomach is neutralized which helps to maintain a stable pH or level of acidity.
A horse that can graze throughout the day can balance their stomach pH level between 2 and 4.
If horses go for more than 3 to 4 hours without food, the stomach pH drops as acids continue to be produced but are not buffered. This creates the perfect environment for ulcers to form.
Given the causal role that excessive acidity plays in the development of ulcers, it is understandable why the use of antacid drugs and supplements is considered to be beneficial for preventing ulcers.
However, this is not an effective long-term therapeutic target. As we will discuss in further detail below, there is a pronounced rebound effect in horses on antacids which can cause recurrence of ulcers.
Common Causes of Equine Gastric Ulcers
- Diet composition
- Feeding regimen or intermittent feeding
- High intensity exercise
- Intermittent water intake
- Environmental stressors
- Social environment
- Excessive NSAID use
You can learn more about the top 7 common causes of gastric ulcers in horses in this article.
Treatments for Gastric Ulcers
An ulcer diagnosis in your horse is often paired with Omeprazole treatment. Omeprazole is the most commonly prescribed ulcer drug that works as a proton pump inhibitor. 
As a proton pump inhibitor, Omeprazole limits the secretion of gastric acids in the stomach. This results in a raised stomach pH. (Lower acidity = higher pH.)
Another drug used for ulcer treatments is Cimetidine. Cimetidine is an H2 receptor antagonist. While the mechanism is slightly different from Omeprazole, they both raise the stomach pH levels.
Raising the stomach pH may temporarily help with treating ulcers. However, it can have negative effects on digestion by impairing the breakdown of food by digestive enzymes.
Subsequently, when treatment stops, the stomach responds with an over-production of acids. 
This is referred to as rebound acid hypersecretion and results in an unnaturally low pH. The low pH causes ulcer rebound, in which new ulcers form. This is why ulcers tend to recur at very high rates for horses when they stop using Omeprazole
This phenomenon has both veterinarians and horse owners searching for alternatives, such as natural antacid supplements.
Antacid Supplements for Horses
How do antacids work to prevent gastric ulcers in horses? As the name suggests, they work to counteract acids.
Common antacids for horses include:
- Aluminum hydroxide
- Magnesium hydroxide
- Calcium hydroxide
- Dicalcium phosphate
- Calcium bicarbonate
- Sodium bicarbonate
All of these compounds neutralize acids. It is the hydroxide or bicarbonate portion of these molecules that buffer acids, increasing gastric pH levels.
Antacids can achieve this by binding to free hydrogen ions (acid) to create water. Some of these can bind pepsin and other substances that can damage the gastric mucosa. 
Several studies have investigated the effects of antacids in horses and have shown that they can increase the pH of the stomach.
In 1992, horses were supplemented with 120 ml of an antacid supplement (8.1 g aluminum hydroxide and 4.8 g magnesium hydroxide) and monitored for six hours post-administration. 
The gastric pH of these horses increased to greater than 4. (For reference, pure water has a neutral pH of 7.)
After four hours, the pH dropped back down to its natural level.
In 1996, a similar antacid supplement was tested in adult horses. This supplement contained 30 grams of aluminum hydroxide and 15 grams of magnesium hydroxide. 
The gastric pH levels were raised to 5 for two hours post-administration.
Multiple studies have since confirmed this short-lived effect of antacids.
However, more recently veterinarians and researchers have been discouraging the use of antacids for equine ulcers.
Here we discuss why antacids do not work in the long-term for gastric ulcers and better alternative options to use instead.
Why Antacids do NOT work
1. No Evidence of Ulcer Healing
In the two studies previously described, the researchers only analyzed pH levels. They did not evaluate the effects of antacid supplementation on the presence of gastric ulcers.
Although antacids raise gastric pH levels in horses, they have not been shown to support ulcer healing in research studies.
In one study, a pelleted antacid supplement that neutralized the gastric environment for 6 hours was found not to heal ulcers.
Horses might show improvements in ulcer symptoms such as low appetite, chronic colic or poor disposition on this product.
However, the underlying ulcers are not healed through the use of antacids. Continuous use is required to see any effect on symptoms. 
2. Short-Term Effects Only
Previous studies have demonstrated that adding antacids to your horse’s feeding program can raise gastric pH. However, this effect only lasts for 2 to 4 hours.
You would need to provide antacids many times throughout the day for your horse to continue to experience a benefit.
Research shows that once ulcers have developed, it can take up to 4 weeks for complete healing to occur.  Unless you can administer antacid supplements every 4 hours for four weeks straight, there is not enough time for the ulcers to heal.
Furthermore, no studies have found that antacid supplementation leads to long-term healing of gastric ulcers.
Therefore, the long-term efficacy of antacids is low.
3. Goes Against Natural Physiology
We have now established that antacids can raise stomach pH levels for a short period. There are two major reasons why that is not a good thing:
It reduces the acidifying capacity of the stomach:
The stomach is acidic for a reason. The acidic environment activates digestive enzymes to begin breaking down food.
Antacids raise the pH to values greater than 5, which interferes with the activity of these enzymes. Neutralize the acids, and you hinder the first step in effective digestion.
Over short periods of time, this might not have a negative effect. But continued interference with digestive processes can lead to secondary nutrient deficiencies and reduced feed efficiency in your horse.
When we interfere with the activity of digestive enzymes, we risk causing problems with nutrient assimilation, even if the horse is being fed a nutritious diet.
Long-term nutritional deficits can have wide-ranging negative impacts on your horse’s overall well-being.
It can allow harmful bacterial growth in the stomach:
Bacteria live all throughout the digestive tract in horses – even within the stomach. Only certain species of bacteria are able to withstand the acidic environment of the stomach.
This helps to keep pathogenic (harmful) bacteria in check while enabling beneficial probiotic bacteria to colonize the gut.
Shifts in pH can result in shifts in the microbial populations, potentially causing dysbiosis or an imbalanced microbiome.
Dysbiosis can occur in the gastrointestinal tract when pH is elevated for prolonged periods, affecting the activity of various microbes that influence the digestive process. 
4. Does Not Target the Root Cause
Antacids may increase your horse’s gastric pH levels, but they will not address the root causes of ulcers.
Equine gastric ulcers are not usually caused by low pH in isolation. Usually, there are underlying factors that contribute to excessive acidity in the stomach.
If these root causes are not addressed, ulcers are likely to persist and recur in your horse.
Risk factors associated with the development of gastric ulcers can include: 
- High grain intake
- Extended intervals without feeding
- High intensity exercise
- Insufficient water intake
- Environmental stressors
- Trailering and transportation
- Social environment
- Excessive NSAID use
Each of these risk factors has a unique mechanism of action that can contribute to gastric ulcers.
Antacids can temporarily reduce the risk of ulcers forming. However, if the underlying causes are not addressed, ulcers are almost sure to return. Antacids are only a temporary fix.
Antacids also do not directly support tissue healing or the formation of a protective barrier between gastric acid and stomach tissue. They do not address inflammation or oxidative stress in the stomach lining, nor do they support the function of the immune system.
Compared to other anti-ulcer supplements that do address the root causes of ulcers, antacids are much less effective.
If your horse is prone to ulcers, we recommend consulting with a qualified equine nutritionist and your horse’s veterinarian to optimize their feeding program and management.
This will help you develop strategies to naturally mitigate the risk of developing gastric ulcers and support tissue healing without relying on antacids.
5. Adverse Effects
In general, antacids have a wide margin of safety and clinical overdose is rare. However, side effects can occur, particularly if they are overused.
Aluminum hydroxide can cause loss of appetite and constipation. Poor appetite is particularly undesirable as intermittent feed intake is a major known risk factor for ulcers in the first place.
Magnesium hydroxide is a common antacid that is also used in equine veterinary medicine to induce diarrhea in mild cases of colic. The laxative effect of magnesium hydroxide can cause electrolyte imbalances through excess excretion of potassium.
Potassium deficiency can result in muscle cramping among horses on long-term antacid protocols.
6. Acid Rebound and Ulcer Recurrence
Any time you try to counter the effects of a physiological regulatory process, the law of unintended consequences comes into play.
The horse’s body works very hard to maintain a stable pH environment in the gut. This is why horses on the proton-pump inhibitor (PPI) Omeprazole often experience an over-production of acid following cessation of treatment.
As soon as you stop administering PPIs to your horse, acid rebound occurs. The horse begins to produce even more gastric acid, resulting in a lower pH and high rate of ulcer recurrence.
Antacids gained popularity as a natural alternative to drug therapies because they have a different proposed mechanism of action.
It was thought that because antacids did not inhibit the secretion of gastric acids, they would not result in ulcer rebound.
However, laboratory observation of tissues in culture suggests this may not be the case.
The calcium ion, released from calcium carbonate or other salts, has been shown to increase acid production by direct stimulation of ion-gated channels. This may result in increased acid production for horses on antacid supplements.
However, more research is needed to understand this counter-regulatory effect. It is unclear whether this significant in the live animal and whether this in itself warrants discontinued use of antacids. 
7. Big Cost for Little Benefit
Lastly, antacid supplements are costly. One popular brand of equine antacid supplements costs $4.20 per day.
This is still significantly cheaper than Omeprazole treatment, which can cost $700.00 a month or more for horses.
But considering the lack of long-term efficacy for these supplements and potential negative effects on digestion, there are better options out there that are more cost-effective.
Alternatives to Antacids
So, what is the best alternative to antacids? There are many ways to naturally prevent ulcers in horses.
Below, we have highlighted some of the most effective strategies.
To reduce ulcer risk, horses that are stall confined should have constant access to hay. 
This will increase the amount of time a horse is feeding and minimize time spent with an empty stomach.
Ideally, horses should have more pasture time so they can graze throughout the day. This is the best way to support a species-appropriate lifestyle for your horse.
Research shows that horses choose to eat more throughout the day when turnout is increased compared to horses that are stall confined. 
Always provide your horse with access to water and offer free-choice loose salt at all times.
Salt intake helps to ensure your horse is adequately hydrated by encouraging them to drink more. Loose salt is more effective than a salt block for encouraging water consumption.
Hydration is important because water intake helps to dilute acids in the stomach and can reduce ulcer risk.
The type of hay you feed to your horse can also impact ulcer risk. For example, alfalfa hay has a higher protein content and lower calcium levels which can buffer stomach acid. 
If your horse has a higher energy requirement and you feed grain to meet caloric needs, it is best to provide multiple small meals throughout the day.
Large meals of grain and other concentrates can cause fermentation in the stomach and production of volatile fatty acids which lower gastric pH. Smaller meals ensure that fermentation in the stomach is minimal and that most starch digestion occurs in the small intestine.
Incorporating dietary fat instead of grains can provide horses an alternative energy source. Flax oil, canola oil, or Mad Barn’s w-3 Oil can help minimize the risk of ulcers while still meeting the horse’s energy needs.
Equine management plays a big role in ulcer risk. Consider the following changes to your horse’s lifestyle and routine to help keep them ulcer-free in the future: 
- Minimizing the use of NSAIDs
- Reducing your horse’s stress level
- Minimizing intensive exericising
- Limiting travel
- Increasing turnout and limiting stall confinement
- Ensuring proper socialization
- Maintaining a routine and/or feeding regimen
- Limiting environmental changes
There are several safe and natural supplements for horses with ulcers that are well supported by research studies.
Ulcer supplements can work in a variety of ways to support a healthy gastrointestinal tract and improve gut barrier function.
Some ingredients that have good research data to support their use include:
- Probiotics and prebiotics
- Slippery Elm Bark
- Active yeast cultures
- Digestive enzymes
- Bioactive proteins
- Marshmallow extract
- Aloe Vera
- Licorice Root Extract
For a safe and natural alternative to antacids, Mad Barn’s Visceral+ supplement has been clinically studied in horses with ulcers.
Visceral+ has been shown to help maintain healthy stomach tissue and support the immune system. It was formulated in conjunction with veterinarians who were tired of treating gastric ulcers with expensive proton-pump inhibitors only to see very high rates of relapse post-treatment.
The most comprehensive supplement ever developed for equine ulcers, Visceral+ contains proven ingredients such as lecithin, Sachharomyces cerevisiae yeast, magnesium, milk thistle extract, meadowsweet, slippery elm, and a 20 billion CFUs 5-strain probiotic blend.
Visceral+ provides complete nutritional support for your horse’s digestive system from stomach to colon. Unlike antacids, Visceral+ does not inhibit or interfere with the natural production of stomach acid.
Visceral+ works with the horse’s natural biology to help maintain the integrity of stomach and intestinal tissue, support the immune system and balance the equine microbiome.
Over-the-Counter Antacid Supplement
- Description: Aluminum-based antacid (Aluminum Phosphate) product to combat gastric ulcers and maintain normal stomach function
- Quantity: 25 lbs (400 oz)
- Cost: $156.95
- Feeding rate: 16 oz per day (adult horse)
- Cost Per Day: $156.95
- Description: Complete gut health supplement clinically tested in horses with ulcers and shown to work
- Quantity: 5 KG (1.1 LB)
- Cost: $160.00
- Feeding rate: 80 g per day (adult horse)
- Cost Per Day: $2.58
Discuss any feeding program changes with our qualified equine nutritionists. If you think your horse has gastric ulcers please contact your veterinarian to decide on the best treatment plan.
Is Your Horse's Diet Missing Anything?
Identify gaps in your horse's nutrition program to optimize their well-being.
- Hoffman C.J. et al. Survey of feeding practices, supplement use, and knowledge of equine nutrition among a subpopulation of horse owners in New England.. J Equine Vet Sci. 2009.
- Videla R. and Andrews F.M. New perspectives in equine gastric ulcer syndrome. Vet Clin North Am Equine Prac. 2009.
- Sykes B.W. A free ride: Is long-term omeprazole therapy safe and effective?. Equine Vet Ed. 2021.
- Melo S.K.M. et al. A proton-pump inhibitor modifies the concentration of digestion biomarkers in healthy horses.. J Equine Vet Sci, 2014.
- Buchanan B.R. and Andrews F.M. Treatment and prevention of equine gastric ulcer syndrome.. Vet Clin N Am Equine. 2003.
- Salisbury B.H. and Terrell J.M. Antacids. StatPearls Publishing. 2020.
- Murray M.J. Grodinsky C. The effects of famotidine, rantidine and magnesium hydroxide/aluminium hydroxide on gastric fluid pH in adult horses. Equine Vet J Suppl. 1992.
- 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.
- Cipriano-Salazar M. et al. The Dietary Components and Feeding Management as Options to Offset Digestive Disturbances in Horses. J Equine Vet Sci. 2019.
- Toribio R.E. Disorders of calcium and phosphate metabolism in horses. Vet Clin N Am Equine. 2011.
- Igbokwe I.O. et al. Aluminum toxicosis: a review of toxic actions and effects. Interdiscip Toxicol. 2019.
- Hade J.E. and Spiro H.M. Calcium and acid rebound: a reappraisal. J Clin Gastroenterol. 1992.
- Murray M.J. and Eichorn E.S. Effects of intermittent feed deprivation, intermittent feed deprivation with rantidine administration, and stall confinement with ad libitum access to hay on gastric ulceration in horses. Am J Res. 1996.
- Nadeau J.A. et al. Evaluation of diet as a cause of gastric ulcers in horses. Am J Vet Res. 2000.
- Nadeau J.A. et al. Effects of hydrochloric, acetic, butyric, and propionic acids on pathogenesis of ulcers in the nonglandular portion of the stomach of horses. Am J Vet Res. 2003.
- Pagan, J.D. Gastric Ulcers in Horses: A Widespread but Manageable Disease. Aus Equine Vet. 1998.
- Young, Amy. Equine Gastric Ulcer Syndrome. UC Davis. School of Veterinary Medicine. July 29, 2019.