Equine Gastric Ulcer Syndrome (EGUS)

No matter how long you have been a part of the equine world, at one time or another you have probably feared ulcers causing your horse’s subtle changes in behavior, difference in athleticism, or even signs of colic. With a thorough understanding of the syndrome, preventative measures can be taken.

What is EGUS?

The horse’s upper gastrointestinal system begins with the large molars grinding the hay in a side-to-side motion, breaking up the food into small particles. Those become a “bolus” that proceeds from the oral cavity into the esophagus. The esophagus is the muscular tube that moves food into the stomach. The entrance into the stomach is known as the “cardia,” and it’s a one-way valve in the horse. This means that horses are unable to vomit. Stomach ulcers are sores on the stomach wall caused by excess acid.


2015-04-Horse-StomachWithin the stomach, there are two distinct regions. The upper squamous portion of the stomach, above the margo plicatus, is less protected and thus more vulnerable to ulcers. The lower glandular portion of the stomach is lined with glands that secrete gastric fluids like acid and enzymes to help break down food. It also secretes bicarbonate and mucus to protect the mucosal lining. Because of this, ulcers are not typically present in the lower, glandular portion. Ulcerations do, however, tend to occur around the pylorus, which is the entrance into the small intestine.

In comparison to most other species, the horse has a relatively small stomach. This means that they have trouble handling large amounts of food at one time. A horse in its natural environment will normally graze small amounts throughout a 24 hour period. Grazing keeps a small amount of food in the stomach and increases salivation. Saliva has a high amount of bicarbonate, which helps decrease the stomach acidity level and protect the layers of the stomach. Domestication has changed this, and now horses are fed grain 2-3 times a day followed by forage a few times a day. These larger feedings with high starch and sugar content exaggerate a higher gastric pH, causing inflammation and disruption of the protective barrier in the gastric environment.


Many factors can cause EGUS. This includes stress, improper feed management, parasites, overuse of NSAIDs, sickness, pain, unsuitable housing practices, inclement weather, and many more.


Clinical signs of EGUS are different in every horse. Some horses do not show any clinical signs until the condition is very serious. Common clinical signs include but are not limited to: discomfort while tightening the girth, grinding teeth, lack of appetite, weight loss, loose manure, increased gas production, decreased athleticism, changes in behavior, and low grade colic episodes.

The only way to definitively diagnose ulcers is through gastroscopy. This procedure is easy to perform and minimally invasive. It allows for evaluation of the esophogus, sqamous and glandular regions of the stomach, and opening to the small intestine (pylorus). It also allows the veterinarian to create a specific treatment plan based on the individual findings as well as a long-term prevention and management plan for that specific horse.

Since feed material can prevent a complete evaluation of the stomach, in order to diagnose EGUS horses are fasted for a minimum of 12 hours. To minimize stress, the horse can be mildly sedated with a short-acting tranquilizer. The gastroscope is inserted through the nostril and down the esophagus into the stomach. Since the stomach will be smaller due to the fasting, air is placed into the stomach to allow the veterinarian to observe the stomach in its entirety. The procedure is very safe, and a complete evaluation takes 10-20 minutes. Once complete, the ulcers are graded on a scale from 0 (no ulcers present) to 4 (severe).


Treatment is a multi-step process that involves multiple management techniques, including feeding changes and possibly medications, depending on severity. The Cheshire Horse carries a variety of ulcer supplements to aid in the treatment of ulcers.

Horse Owners Workshop 4/30

Join us at our Horse Owners Workshop on Thursday, April 30th for more information about gastric ulcers and ways that you can keep your horses healthy long term.

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