All About Gastric Ulcers

The horse’s digestive system has evolved over thousands of years and is not well-suited to the habits of well-meaning humans. Given the small size of the horse’s stomach, it’s essential that it eat small amounts of food frequently, as it is not equipped to handle large amounts of food at once. Ideally, the horse needs to graze almost constantly and failing that, it should be fed several small meals throughout the day on a set schedule.

There are a number of factors to consider when developing management techniques for your horse. Like humans, each horse will have different metabolic requirements which will vary throughout the year. Food requirements will vary based on work, temperament, and body condition of the horse. A routine should be established and maintained to make sure the horse is eating frequently throughout the day, allowing for seasonal variations to account for changes in daylight hours and time spent at pasture.

The highly acidic stomach of the horse

The horse’s stomach is lined by a mucous membrane called the gastric mucosa. It produces a highly acidic, enzymatic secretion that initiates the digestion of protein. Muscular activity in the stomach mixes boluses of food with the digestive fluid until they are reduced to small particles and solubilized before passing into the small intestine.

However, the gastric mucosa only protects part of the horse’s stomach. The stomach of a horse is divided into two regions. At the top is the non-glandular squamous or esophageal region that is lined by the same tissue that is found in the esophagus. The bottom region of the stomach is the glandular gastric mucosa, which is similar to the human stomach. But unlike the human stomach, which only produces acid in response to food, the horse’s stomach is constantly producing acid, up to 9 gallons per day.

Manageable causes of gastric ulcers

The primary causes of gastric ulcers are a combination of infrequent feeding, type of feed, exercise and travel.

Importance of grazing: Under natural grazing conditions, where the horse has a near constant flow of food through its system, the stomach acid is neutralized by food and saliva. But under modern management practices, a horse’s eating patterns are vastly altered and the prevalence of gastric ulcers is high. The highest rates of occurrence are in performance and show horses and any other horse that is fed a restricted and/or grain-based diet. Foals are also highly susceptible. Their stomachs begin to produce gastric acid as young as 2 days of age. 

Type of feed: Roughage is the best thing a horse can eat to help mitigate ulcers. Because of the amount of chewing it requires, eating roughage stimulates more saliva production which in turn helps neutralize stomach acid. In contrast, concentrated feeds and grain increase acid production in the stomach and require less chewing, which means less saliva is produced.

Exercise & Travel: There are many disruptions to the natural grazing routine of the horse. When engaged in exercise, particularly in the case of racehorses and show horses, they are prevented from grazing and are often forced to fast for long periods of time. The potential for damage in these situations is two-fold. In addition to the normal buildup of stomach acid, various stresses (exercise, transit) can increase acid production and decrease blood flow to the stomach, making it more susceptible to injury.

Overeating: Although less frequent, ulcers can also develop if the horse’s stomach is too full, thereby displacing gastric acid and causing it to come into contact with the upper, more delicate region of the stomach.


Ulcers occur most frequently in the upper region of the stomach, and occasionally in the lower region and the small intestine. Signs that your horse may have an ulcer include:

  • Reduced appetite
  • Slow eating
  • Change in attitude
  • Mental dullness
  • Irritability
  • Reluctance to work
  • Poor physical condition
  • Poor hair coat
  • Excessive time spent lying die
  • Mild colic
  • Weight loss
  • Loose feces
Diagnosis and Treatment

Gastric ulcers are diagnosed with a gastric endoscopy (gastroscopy) to confirm the presence, severity, and location of the ulceration. This is a minimally invasive procedure that allows the veterinarian to view the esophagus, both regions of the stomach and a segment of the small intestine.

Treatment consists of a combination of management practices and medication. The two main types of medication used in the treatment of ulcers are H2 blockers and acid pump inhibitors. H2 blockers partially limit acid production by blocking the histamines that stimulate acid production in the stomach. Acid pump inhibitors completely stop the production of stomach acid.

In addition to medications, it is important to address the root causes of ulcers and adapt management practices by increasing the amount of roughage in the diet, allowing the horse to graze for at least part of the day, increasing the frequency of feedings, and avoiding or decreasing the amount of grain. Limiting stressful situations like intense training and transportation will also be beneficial.


Clyde Vet Group. Ulcers – “How Susceptible is Your Horse?” Retrieved from

Foster & Smith. “Equine Gastric Ulcer Syndrome.” Retrieved from 

Livesey, M. “The Structure, Function and Dysfunction of the Equine Digestive System.” University of Guelph Equine Research Centre. Date unknown.

Nieto, J. (2012). “Diagnosing and Treating Gastric Ulcers in Horses.” Retrieved from


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