Have you noticed changes in your horse such as weight loss, a dull coat, disinterest in feeding or crib chewing that have resulted in poor performance? Your horse might be experiencing stomach pain, most likely due to gastric ulcers.

Equine Gastric Ulcer Syndrome (EGUS) occurs when sores develop on the lining of the horse’s stomach. The physiochemical barrier that usually protects stomach tissue is worn down and digestive acids cause painful lesions in the stomach’s lining.

In addition to causing discomfort in your horse, gastric ulcers can present with hindgut ulcers which can impair nutrient absorption leading to a wide range of health and behavioural problems.

This condition is known to affect 60-90% of performance horses particularly when travel, high-intensity exercise and long periods without feeding occur. It also occurs at high rates in pleasure horses and young foals.

Research shows that any horse that undergoes stall confinement, has inconsistent access to feed, is fed grain or concentrates, or is trailered is at risk of developing ulcers.

This article will guide you through the different types of gastric ulcers, their causes, symptoms and how to treat and prevent ulcers in horses.

What are Gastric Ulcers?

Ulcers are painful sores that can occur along the entire digestive tract of horses but appear most commonly in the stomach and to a lesser extent in the hind gut. Equine Gastric Ulcer Syndrome (EGUS) is a scientific term that describes horses that have ulcers in their stomach.

The stomach has two main sections, the upper squamous region and the lower glandular region. The squamous region is particularly prone to ulcers developing.

Gastric Ulcers in Horses

The glandular region produces stomach acid, but also produces bicarbonate and mucous to protect the tissue in this area from the acid. These substances form a barrier that makes the lining of the glandular region less prone to ulcers.

The squamous region does not have these natural defenses against stomach acid and accounts for 80% of all gastric ulcers.

A horse’s stomach produces acid all throughout the day. This put them naturally at high risk for developing gastric ulcers, particularly during times when there is no food in the stomach to help buffer the acid.

In the wild, horses graze up to 16 hours a day. They are normally protected from ulcers due to the continuous presence of high-fibre food in their stomach.

However, horses kept in stall confinement with limited turnout during the day may go long stretches of time between eating. An empty stomach increases the risk of ulcers forming.

There are many other factors that contribute to the high rates of gastric ulceration in horses. These factors as well as strategies for mitigating ulcer risk like using Mad Barn’s Visceral+ ulcer support supplement will be covered in further detail below.


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Equine Ulcers Signs & Symptoms

How can you tell if your horse has ulcers? The only definitive way to diagnose EGUS in your horse is by having a veterinary checkup to perform a gastroscopic exam.

Your vet will look into your horse’s stomach and upper intestine with a gastroscope to see whether there are ulcers present, how severe they are and their location.

But even without an exam by your vet, there are some common signs and symptoms to look out for as evidence that your horse may have ulcers. If you think your horse is affected, a visit from the vet to perform a scope is warranted.

Signs and symptoms of gastric ulcers in horses are generally non-specific and can vary greatly between horses. Many horse owners note that their horse is “just not looking right”.

Some common symptoms include: [1]

  • Poor appetite or “picky eating”
  • Poor body condition or weight loss
  • Chronic diarrhea
  • Poor coat condition or a rough coat
  • Bruxism or teeth grinding
  • A more aggressive or nervous disposition
  • Increased stereotypic behaviours such as cribbing
  • Acute or recurrent colic
  • Poor performance
  • Sensitivity in the girth area
  • Excessive recumbency
  • Stretching to urinate
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What Causes Equine Ulcers?

1. Diet and Feeding

Not only does feed composition affect ulcer risk but also the frequency and pattern of feeding. Horses have evolved to graze on pasture for the majority of their day, consuming roughage regularly.

Current equine management practices mean that many horses do not have regular access to pasture and can go long periods of time with no food in their stomach.

With intermittent feeding (i.e. having long intervals between meals), the horse’s stomach is empty, and the continuous production of acid irritates the lining of the stomach and can cause ulcers.

When a horse eats a meal, the food itself and bicarbonate from saliva neutralize the acidity in the stomach, mitigating ulcer formation.

2. High Grain Consumption

Feed composition can have a large effect on ulcer risk. Grain is easier to chew and therefore does not produce as much acid-neutralizing saliva as hay does. Saliva production during consumption of hay is approximately double that produced during intake of an equivalent amount of grain. [2]

In addition, grain empties out of the stomach more rapidly than hay leaving longer periods of time with an empty stomach that is susceptible to ulcer formation.

A high starch or grain intake can lead to local volatile fatty acid production in the stomach which further lowers pH and increases ulcer risk. [3]

Exceeding 2 kg of grain per day approximately doubles the likelihood of gastric ulcers.

3. Intensive Exercise

Approximately 95% of endurance horses and racehorses have gastric ulcers. This increases to 100% when you just consider horses that are actively racing. Racehorses have an increase in prevalence, lesion severity and number of lesions in the squamous mucosa associated with long durations of intense exercise. [4]

There are several reasons why performance horses have such high rates of gastric ulcers.

The greatest contributor is increased abdominal pressure during exercise which compresses the stomach, pushing acidic contents to acid-sensitive areas of the stomach that are prone to developing ulcers.

In addition, if ulcers are already present, reduced blood flow to the stomach during exercise hinders their healing.

Horses in training or competition often go long intervals without access to feed, which increases the time spent with an empty stomach in which acid is unbuffered by stomach contents.

Furthermore, the stresses of travel, frequent changes in environment and workload contribute to their high risk of ulcers.

According to the American Association of Equine Practitioners, “Even typical training and recreational showing have been shown to induce ulcers within a five to seven day period.” [5]

4. Intermittent Access to Water

During training and competition there can be long periods of time without access to water, particularly during transport.

Intermittent access to water increases the chances of developing gastric ulcers in all parts of the stomach.

Turnout without constant access to water, or frozen water in the winter, might also increase the risk of ulcers.

Giving oral electrolyte solutions repeatedly to horses in competition has also been shown to increase the number of ulcers and the severity of the lesions. [6]

5. Physical Stress

Slight changes to a horse’s routine and living conditions can induce stress which contributes to ulcer risk. When stress hormones in your horse are elevated, it can result in a cascade of hormonal changes that make your horse more susceptible to ulcers forming.[7]

The major stress hormone is cortisol. When this hormone is secreted, it results in lower levels of prostaglandin being produced. This causes the pH levels in the horse’s stomach to decrease, weakening the protective barrier in the stomach. Over time, the lining of the stomach is eroded, and ulcers can occur.

Stressful events such as travel, change in environment and illness can predispose horses to higher cortisol levels and higher risk of ulcers. Horses that are recovering from an injury often develop ulcers when they go on stall rest.

Stall confinement can also induce stress and lead to ulcers even with free-choice hay available. Stall confinement may lead to stereotypical behaviours like cribbing that can hinder proper feeding behaviours. Generally, horses that are housed in stalls are fed two large meals per day that are high in grain which increases the risk for ulcers. [8]

6. Social Environment

A major factor that can contribute to the formation of ulcers in your horse is their social environment. Horses are social creatures and are affected by their surroundings.

Horses that experience a change in the herd population are at high risk of developing ulcers.

Being introduced to a new grouping, experiencing the addition of a new horse or departure of a familiar horse, or a change in the condition of a nearby horse can all influence your horse’s stress levels.

Research also shows that horses kept on their own have a higher risk of gastric ulceration.

7. Anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) used for treatment of lameness or other illnesses can contribute to ulcer risk. If your horse has been on phenylbutazone or other NSAIDs for longer than one week, they are at high risk for gastric ulceration.

NSAIDs may cause ulcers by decreasing production of prostaglandins which normally help with blood flow to the stomach and production of mucous defenses.

NSAIDs work by inhibiting the effects of the inflammatory prostaglandin COX-2. However, these drugs also block the effects of another prostaglandin COX-1 which has a protective effect on the stomach.

While some newer anti-inflammatory drugs used in horses target COX-2 specifically without blocking COX-1, many horse owners continue to use conventional NSAIDs which are non-specific.

If your horse is prescribed a regimen of NSAIDs, ask your veterinarian about ways to reduce the risk of ulcers forming.

Diagnosis of Gastric Ulcers

Gastric ulcers can be difficult to diagnose in horses because of subtle, inconsistent signs. Indirect, non-invasive tests such as measuring sucrose permeability have been proposed but are currently unreliable.

Gastroscopy which visually inspects all areas of the stomach and proximal intestine is the only reliable method to definitively identify ulcers.

Gastroscopy also provides information about the severity (size and depth) and number of lesions to further inform treatment.

However, severity and clinical signs don’t always match. In some cases, horses with minor lesions may show more clinical signs than horses with severe lesions or vise versa. [9]

Gastroscopy is also not accessible to all horse owners due to the high cost. Given the very high prevalence of ulcers in performance horses and even pleasure horses, it may be prudent to assume that your horse is at risk of ulcers and to take steps to mitigate the risk in the future.

How to Support Gastric Health

Nutritional strategies

To decrease the risk of developing ulcers, horses in stalls should have access to free-choice hay and water all day long. This will increase the frequency of feeding and amount of time with hay in the stomach.

Alfalfa hay or cubes/pellets can also be beneficial for decreasing the number and severity of ulcers. This forage is high in calcium which has been shown to decrease gastric acid production from cells in the stomach. However, this is likely a transient effect immediately following the meal and could result in higher acid production later on. The higher protein content of alfalfa hay can buffer stomach acid to increase gastric pH. [10]

It is typically recommended to include alfalfa hay at no more than 10-20% of the forage content of the diet.

One study compared a diet of alfalfa hay + grain (reflective of a diet for horses in training) to a diet of bromegrass alone (reflective of a maintenance diet). Despite the presence of grain in the diet, the alfalfa hay resulting in a higher gastric pH over the first 5 hours after the meal compared to bromegrass alone. [10]

The diet with alfalfa hay also decreased the number and severity of ulcers. [10]

Grain and starches should be divided into several smaller meals when possible to minimize bacterial fermentation in the stomach which contributes to acid production.


The most common treatment of existing ulcers is omeprazole (GastroGard or UlcerGard) which is a proton-pump inhibitor that blocks acid production by the stomach. Omeprazole is most successful in treating squamous ulcers. [11]

Sucralfate is often used as an adjunct therapy to proton pump inhibitors. When it enters the acidic environment of the stomach it forms a viscous paste that can bind to ulcers forming a protective barrier that prevents further damage. [11]

Misoprostol îs a prostaglandin analogue that is mot commonly used to treat glandular ulcers. Is is superior to treating glandular ulcers compared to omeprazole alone or the combination of omeprazole + sucralfate. [12]

Lowering acid production in the stomach allows the stomach to heal during treatment. However, there is frequent recurrence when treatment stops and acid production resumes, putting the horse at risk again.

There can also be compensatory increase in acid production after treatment ends further increasing recurrence.

These pharmaceutical approaches to treating ulcers face several other problems:

  1. They do not address the root cause of ulcers (i.e. stress, NSAID use, etc.)
  2. They may decrease activity of digestive enzymes, resulting in higher levels of protein reaching the hindgut
  3. This can cause secondary hindgut dysfunction due to excess fermentation
  4. They may reduce the horse’s protection from pathogens in the gut


Calcium carbonate or calcium hydroxide are commonly used buffers that help temporarily neutralize stomach acid. However, these provide only transient relief and if overused they can result in increased acid production.

Proton pump inhibitors like omeprazole or other acid reducers/buffers provide relief during treatment and can allow ulcers to heal. However, the chance of ulcers reappearing after these treatments are discontinued is very high.


Mad Barn’s Visceral+ is a pelleted equine supplement.

Visceral+ is designed to maintain gastric and hindgut health while supporting the immune system. hindgut function and provide immune support.

It can be used alone or in combination with omeprazole.


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  • Our best-selling supplement
  • Maintain stomach & hindgut health
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  • 100% safe & natural

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  1. Buchanan, BR and Andrews, FM Treatment and prevention of equine gastric ulcer syndrome. Vet Clin N Am-Equine. 2003. View Summary
  2. Meyer, H et al. Investigations of saliva production and chewing in horses fed various feeds, in Proceedings of the Equine Nutrition and Physiology Society, East Lansing, MI, pp.38-41.
  3. Nadeau, JA 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. View Summary
  4. Murray, MJ et al. Factors Associated With Gastric Lesions in Thoroughbred Racehorses. Equine Vet J. 1996. View Summary
  5. McClure, Scott. Equine Gastric Ulcers: Special Care and Nutrition. AAEP. 2016.
  6. Holbrook, TC et al. Effect of Repeated Oral Administration of Hypertonic Electrolyte Solution on Equine Gastric Mucosa. Equine Vet J. 2005. View Summary
  7. Scheidegger, MD et al. Increased adrenocortical response to adrenocorticotropic hormone (ACTH) in sport horses with equine glandular gastric disease (EGGD). Vet J. 2017. View Summary
  8. Videla, R and Andrews, FM .New Perspectives in Equine Gastric Ulcer Syndrome. Vet Clin N Am-Equine. 2009. View Summary
  9. Murray, MJ et al. Gastric Ulcers in Horses: A Comparison of Endoscopic Findings in Horses With and Without Clinical Signs. Equine Vet J Suppl. 1989. View Summary
  10. Nadeau, JA et al. Evaluation of diet as a cause of gastric ulcers in horses. Am J Vet Res. 2000. View Summary
  11. Sykes, BW et al. European College of Equine Internal Medicine Consensus Statement—Equine Gastric Ulcer Syndrome in Adult Horses. J Vet Intern Med. 2015. View Summary
  12. Varley, G et al. Misoprostol is superior to combined omeprazole-sucralfate for the treatment of equine gastric glandular disease. Equine Vet J. 2019. View Summary