diagram of horse's stomach
Squamous ulcers occur in the upper region of the stomach while glandular ulcers occur in the lower region. | The Horse

Gastric ulcers are sores in the equine stomach lining that cause distress and negatively affect performance. An estimated 60% of performance horses and 90% of racehorses have gastric ulcers. The odds of a horse developing gastric ulcers increase with stress such as exercise or life changes.

“Such stresses include training, trailering, and showing … all things we do with our horses all the time, putting our horses at risk,” said Jyme Nicols, PhD, director of nutrition for Bluebonnet and creator of the Feed Room Chemist Podcast during her presentation at the 2024 virtual EquiSummit, held Dec. 3-4.

Where Do Equine Gastric Ulcers Occur?

Horses have one very small (3- to 5-gallon) single-chambered stomach, which functions best when they are allowed to eat small amounts of food all day. The stomach is made up of two key areas: an upper area covered by squamous tissue and a lower covered by glandular tissue. The lower glandular region produces acidic gastric juice and mucus.

“It is very important to know where ulcers are—the squamous, glandular, or both—because location will influence treatment protocol,” said Nichols. “And the only way to diagnose ulcers is to have the horse ‘scoped’ by a veterinarian,” meaning with the use of a gastroscope.

How to Score Equine Gastric Ulcers

In 1999 researchers introduced the term equine gastric ulcer syndrome (EGUS) as an umbrella term for any ulcer in the horse’s stomach. Experts later reported that ulcers in the glandular and squamous region are very different, and the two types should be described independent of one another.

For squamous ulcers, in the upper region of the stomach, veterinarians use a well-established grading system, which describes ulcers based on severity. The scale ranges from 0 (healthy with no ulcers) to 4 (extensive lesions, deep erosions). In contrast, practitioners have no universal scoring system for glandular ulcers (in the lower region of the stomach). Instead, they describe those ulcers based on their physical appearance and specific location (e.g., nodular, flat, raised, depressed, and in the antrum, pylorus, etc.).

Causes and Risk Factors for Equine Gastric Ulcers

“As mentioned above, we ask horses to do things they aren’t designed to do such as training, trailering, and showing,” said Nichols. “They are designed to have their heads down, grazing, in a herd, yet we isolate them in stalls, travel, and hire trainers to work with them. We often feed them meals only twice a day, sometimes with large amounts of grain, and many owners don’t have the luxury of turning their horse out all day.”

Some key risks factors for developing EGUS include:

  • Extended periods without forage. Going six hours or more between forage meals (hay or pasture) increases a horse’s risk, and many horses are going beyond six hours, said Nichols. Extending feeding time and ensuring horses have forage available at all times can help decrease the risk.
  • Insufficient water. Water serves as an excellent buffer for gastric juices, and horses that drink well and always have access to water at all times are less likely to develop gastric ulcers. In contrast, horses with restricted water access are more than two times more likely to have ulcers.
  • Consuming high-starch meals exceeding 2 g/kg of bodyweight doubles the horse’s risk of developing ulcers.
  • Medications such as non-steroidal anti-inflammatory drugs (NSAIDS, e.g., phenylbutazone and flunixin meglumine) increase the risk of glandular disease especially, by damaging the gastric mucosal lining.

Clinical Signs of Equine Gastric Ulcers

 “Signs of EGUS can be subtle, so you have to know your horse and what is normal in order to recognize what is abnormal,” said Nichols.

Subtle behavior changes, such as changes in facial expression when saddling (ear, eye, and mouth position and movements), can suggest the presence of gastric ulcers. Other signs of EGUS can include general irritability and girthiness (e.g., the horse might try to bite cross-ties or you, swish his tail) and changes in performance.

Certain indicators of ulcers can become more apparent, such as dropping condition, losing topline, dull haircoat, and exhibiting signs of colic.

Diagnosing and Treating Equine Gastric Ulcers

Always have your veterinarian perform a gastroscopy on your horse if you think he might have gastric ulcers.

“Be aware that there is no link between glandular and squamous disease,” said Nichols. “Having one does not mean they do or do not have the other. Plus, there is no link between outward signs and the severity of ulcers.”

Treating ulcers mainly involves suppressing acidity in the stomach and protecting the gastric mucosal lining. The most commonly prescribed medications include omeprazole, ranitidine, and sucralfate.

“We also need to consider what led to ulcers in the first place,” said Nichols. “Align their daily lives with how they are physiologically designed—let your horse be a horse.” Management changes such as increasing forage available, reducing stressors in the environment, and limiting changes in routine can help decrease your horse’s risk of developing gastric ulcers.    

Take-Home Message

“Be aware that most horses are at risk of developing gastric ulcers, so pay attention to your horse’s behavior to appreciate early signs,” Nichols said.

Prevent gastric ulcers whenever possible by managing your horse’s diet, the environment, and his stress levels, and work closely with your veterinarian and equine nutritionist to diagnose, treat, and manage EGUS.

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