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Stomach ulcers in your horse

Quick facts

  • Stomach ulcers are a common problem and concern for horse owners.
  • Many factors contribute to ulcers such as stress, medications and exercise.
  • Proper diagnosis can help you create an appropriate treatment plan.

What are stomach ulcers and what causes them?

Gastric ulcers are sores that occur in the lining of the horse’s stomach. They are a common problem in horses that aren’t completely understood.

Many factors can play a role in causing ulcers including:

  • Stress
  • Nonsteroidal, anti-inflammatory drugs (phenylbutazone and banamine)
  • Housing
  • Exercise
  • Diet     

Types of stomach ulcers

The type of ulcers a horse has depends on the location of the ulcer in the stomach. The horse’s stomach has two parts: the squamous and glandular regions. 

Squamous ulcers

Eighty percent of ulcers occur in the squamous region.

  • Squamous refers to the part of the stomach closest to the opening of the esophagus.
  • Skin-like cells cover this region of the stomach. These cells don’t produce stomach acid and as a result, are prone to damage from acid.
  • Horses with ulcers in this region are referred to as having Equine Gastric Ulcer Syndrome (EGUS).

Glandular ulcers

  • Glandular ulcers occur in the glandular region of the horse’s stomach.
  • The glandular region of the stomach contains cells that release acid that’s essential for digesting food.
  • Horses with ulcers in this region are referred to as having Equine Glandular Gastric Disease (EGGD).

Signs of stomach ulcers

Signs of ulcers in adult horses can be vague and may include:

  • Acute or recurrent colic, particularly after eating.
  • Loss of body condition.
  • Performance issues.
  • Changes in attitude.
  • Frequent lying down.

Horses with gastric ulcers may be reluctant to eat grain or may take more time than usual to eat the grain. Gastric ulcers also occur along with many other conditions. Horses are often placed on preventative (lower) or treatment (higher) doses during hospitalization.

Diagnosing ulcers

The best way to diagnose gastric ulcers is by flexible endoscopy of the stomach. In this procedure, a three-meter fiber optic scope is placed in the horse's nose and passed through the esophagus to the stomach. Many horses tolerate this procedure very well and side effects are rare.

Preparing for endoscopy

Restraining feed and water for a period of time before the endoscopy will give clinicians a better view of the stomach.

  • Withdraw food for at least 12 hours before the procedure.
  • Most clinicians prefer the horse doesn’t have water for three to four hours before the procedure.
  • Some horses may require an additional fasting period.


Depending on severity and clinician preference, horses are often given either omeprazole or ranitidine. These drugs work by stopping acid secretion in the stomach, which raises the stomach pH.

Unfortunately, due to breakdown of the active ingredient, the formulation of omeprazole is critically important. Generic or compounded omeprazole usually isn’t effective. 

Treating for ulcers generally lasts a month. Recheck endoscopy can help you determine if your horse needs further treatment.

Author: Micah Bishop, DVM

Reviewed in 2024

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