Gastric Ulcers (ESGUS and EGGUS) in Horses

Key takeaways

Gastric ulcers are sores inside the lining of the stomach. In horses, two types of gastric ulcers have been identified: upper and lower.

  • Ulcers found in the upper area of the stomach are often caused by intense performance demands or stress
  • Ulcers in the lower part of the stomach are associated with nonsteroidal antiinflammatory drugs (NSAIDs) and stress
  • Symptoms of gastric ulcers are typically vague and non-specific, including poor performance, mild colic signs, mild weight loss, and behavioral changes
  • In foals, teeth grinding, poor nursing, and drooling are also noted
  • Diagnosis requires endoscopy
  • Treatment is necessary in severe, ongoing, or chronic cases and involves ulcer medications that reduce the production of stomach acid
  • Dietary and management changes are also recommended
  • The prognosis is typically good, though recurrence is common
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A closer look: Gastric Ulcers (ESGUS and EGGUS) in Horses

In most cases, adult horses show no signs of gastric ulcers. Mild ulcers tend to recover without intervention. Horses with more severe ulcers require prompt veterinary treatment.

The severity of gastric ulcers depend on how deeply the sores have eroded the stomach lining, how many sores there are, and whether any of the sores have burst. Horses with more severe cases often show changes of behavior and poor performance. Some horses may show signs of mild colic, such as:

  • Getting up and down often
  • Rolling
  • Lethargy
  • Tooth grinding

Risk factors

Performance horses are more likely to have gastric ulcers. Horses that travel, have new handlers or new routines, are in poor social standing with other horses, or horses with other causes of stress are also more at risk. Horses that have had nonsteroidal antiinflammatory drugs administered recently and foals are more at risk of ulcers in the lower part of the stomach. In cases where the ulcer perforates (tears open), signs of severe colic are often noted. These include:

  • Getting up and down often
  • Rolling excessively
  • Biting and kicking at the flank to the point that they may injure themselves
  • Sweating
  • Labored breathing
  • Unwillingness to stand up

Horses with the signs of severe colic require emergency veterinary attention.

Possible causes

Gastric ulcers are sores that develop in the lining of the stomach. Ulcers that occur in the upper part of the stomach (also known as equine squamous gastric ulcer syndrome or ESGUS) are caused by acidic gastric juices splashing up into the relatively unprotected tissues that line the upper portion of the stomach. The acid burns holes in the tissue. The splashing of acid is often caused by exertion, such as racing or jumping, especially when the stomach is empty. Stress is also considered a contributing factor.

Gastric ulcers in the lower part of the stomach (also known as equine glandular gastric ulcer syndrome or EGGUS) in adult horses are associated with the administration of nonsteroidal antiinflammatory medications and stress. Possible causes of stress include:

  • Travel
  • Changes in routine or management
  • Changes in handlers
  • Poor position in the social hierarchy of fellow horses

In foals, EGGUS is common due to the underdevelopment of the lower part of the stomach, leaving it vulnerable to the effects of the stomach acid.

Main symptoms

Typically, horses do not show symptoms of gastric ulcers unless they are widespread or severe. The main symptoms of gastric ulcers in adult horses are typically vague and nonspecific.

Testing and diagnosis

Diagnosis typically begins with physical examination. Definitive diagnosis requires endoscopy, where a camera probe is fed into the stomach to visualize the ulcers. In some cases, a presumptive diagnosis is made by administering ulcer medication to a horse who is feeling or performing poorly. If the horse’s mood, pain, and performance improve, the assumption is made that gastric ulcers were the cause.

Steps to Recovery

Horses with mild stomach ulcers typically show no symptoms and recover on their own.

In more severe cases, treatment involves medication that prevents the stomach lining from producing stomach acid, making less acid available to erode the stomach wall.

Management strategies are also a key component of treatment, and include changes such as:

  • Decreasing the intensity of training
  • Increasing turnout
  • Increasing forage consumption, including providing forage access all day
  • Avoiding long-term administration of NSAIDs

In cases where gastric ulcers are severe enough to cause symptoms, prompt treatment is usually successful in resolving ulcers in around 4 weeks. Prognosis with treatment tends to be good to excellent. Recurrence is very common, particularly when horses resume intense training or exercise.

Foals with gastric ulcers are at risk of developing scarring in the areas where the stomach is ulcerated. In some cases, these scars can prevent food from flowing past, requiring surgical removal of the affected tissue. These foals have a guarded prognosis, even with treatment.


Prevention of gastric ulcers focuses on maintaining gut health. Horses require many small meals throughout the day and access to plenty of water. Horses fed a diet that includes alfalfa and other feed that has high alkalinity have a lower risk of developing ulcers. Horses that have increased turnout time on pasture also have a reduced risk compared to stabled horses.

Performance horses sometimes benefit from preventive administration of ulcer medications during periods of high stress. Avoiding stressors such as too much travel, changes in routine or management, and poor social standing among other horses is also recommended.

Are Gastric Ulcers (ESGUS and EGGUS) in Horses common?

Gastric ulcers are very common among horses.

Typical Treatment

  • Ulcer medications
  • Management changes


Frank M. Andrews , DVM, DACVIM-LAIM - Writing for Merck Veterinary Manual
Frank M. Andrews , DVM, DACVIM-LAIM - Writing for Merck Veterinary Manual
Dr. Fernando J. Marqués - Writing for University of Saskatchewan Western College of Veterinary Medicine
Stacey Oke, DVM, MSc - Writing for The Horse
No Author - Writing for The Horse

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