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What are stomach ulcers in horses?

An ulcer is an area of the stomach where the tissue is damaged and eroded. The term Equine Gastric Ulcer Syndrome (EGUS) is used to describe this painful and common condition in horses, which affects the stomach and the first part of the small intestine. Since horses are grazing animals that are intended to graze most of the day, their stomachs constantly produce acid. Because they are typically fed concentrated diets a few times a day, horses are more susceptible to acid buildup, eventually causing ulcers.

What causes ulcers in horses?

Equine ulcers are the result of a repeating cycle of increased acidity, decreased appetite, and the formation of an ulcer—followed by moderate to severe discomfort.

Ulcers in horses can develop within as little as five days.1

Often the result of stress, which causes an increase in stomach acid secretions that damage the stomach lining, ulcers are painful and lead to an aversion to eating. Eating less roughage causes the horse’s digestive tract to become more and more acidic, leading to more ulcerations, appetite suppression, and pain—and the cycle continues.

Factors that can contribute to ulcers include:

  • High-starch diets that increase acid production
  • Strenuous training plans
  • Feeding pattern (fewer meals per day)
  • Certain medications
  • Lifestyle and stress

Although common in performance horses, gastric ulcers can be a problem for all types of horses. Depending on a horse’s age, breed, and activity, the rate of equine ulcers may rise to 93%.2

1. McClure SR, Carithers DS, Gross SJ, et al. Gastric ulcer development in horses in a simulated show or training environment. JAVMA. 2005;227(5):775–777.

2. Murray MJ, et al. Factors associated with gastric lesions in Thoroughbred racehorses. Equine Vet J. 1996;28:368–374.

Symptoms of gastric ulcers

The pain caused by gastric ulcers may cause a change in your horse’s behaviour. Signs of gastric ulcers in your horse may include:

Noticeable signs

Decrease in appetite

Stressed behaviour at feeding time

Weight loss

Dull and rough hair coat

Subtle signs

Change in attitude (for the worse)

Decrease in performance

Resisting to leg yields

Flattening over jumps

Losing speed towards the end of a race

Peculiar signs


Decreased water consumption

Posturing as if to urinate

Ulcers in horses frequently result in colic, a painful and persistent condition.

Read more about signs of ulcers and how they are diagnosed.

Equine ulcer treatment plan

The treatment and prevention of ulcers in horses has recently evolved to include controlling gastric acid production, rather than simply neutralizing it with antacids. The result is faster healing, and less pain and colic.

Treat ulcers in horses.
Check out this free 1-hour webinar

from the FEI and learn more about the causes, types, and symptoms of equine gastric ulcers, including an expert guided gastroscopy, which is used to diagnose ulcers.

View the webinar