McKee-Pownall Equine Services | Health Care FAQ

Health Care FAQ

What Causes Ulcers in Horses?

Stomach ulcers, also known as Equine Gastric Ulcer Syndrome (EGUS), are an important topic in equine health care. Ulcers tend to form when the stomach is irritated by acid production, causing erosions in the stomach lining. Unfortunately this is an extremely common problem, and some studies estimate that 60 – 90% of performance horses are clinically affected. While clinical signs can vary depending on the diet, lifestyle and daily routine, it is important to understand why ulcers happen, how to recognize the risk factors and clinical signs, and what you can do to prevent ulcers from becoming an issue for your horse.

How the Stomach Works

Figure 1 (

Understanding how the equine stomach works is the first step to understanding ulcers. The equine stomach is divided into two distinct parts (Figure 1) – the glandular portion and the non glandular portion. Because horses are designed to continuously eat throughout the day, the glandular portion (about 2/3 of the stomach) has adapted by continuously secreting stomach acid and digestive enzymes, whether food is present in the stomach or not. This acid decreases the pH of the stomach, more so when the stomach is empty. The lower the pH, the more damaging these acids can be to the stomach itself. As a counter measure, the glandular portion also secretes mucus and bicarbonate that help to protect the stomach from the effects of the acid. The remaining 1/3 of the stomach, the non glandular portion, lacks these protective factors and is often the part of the stomach most affected.

What causes ulcers?
Anything that causes excessive exposure of the non glandular portion of the stomach to acid will cause ulcers. This could be either from excessive acid production, lack of food in the stomach, or even delayed emptying of the stomach contents. There are often many factors that contribute including diets that are high in starch, diets that are low in roughage, feeding large meals throughout the day with many hours between meals, intense exercise/training schedules (especially on an empty stomach), and long term use of non steroidal medications. Anything that causes stress to the horse may also play a roll, including excessive stall time, trailering, showing/racing, loss of/addition of a herd mate or even a change in the daily routine.

What are the clinical signs?

Figure 2

Clinical signs of ulcers can vary from horse to horse depending on the severity of the ulcers and the underlying cause. It is important to realize that every horse may show different clinical signs, and often times clinical signs may be very vague and nonspecific.

Things to look out for include:

  • Chronic, mild colics (often after the horse eats grain)
  • Poor appetite or unexplained weight loss
  • Dull hair coat, sour attitude, attitude change
  • Girthy, resents having their stomach brushed, teeth grinding
  • Poor performance, especially when stressed
  • Laying down more than normal
  • Low white blood cell count

How are ulcers diagnosed and treated?
The only way to truly diagnose ulcers is to use an endoscope, or specialized camera, to look at the
stomach lining. This is very useful to determine the degree and severity of ulcers, which in turn helps to determine what the best treatment is. Treatments are designed to reduce stomach acid production and protect the stomach lining. Options include omeprazole, ranitidine, cimetidine and sucralfate. If you suspect ulcers are a problem, speak to your veterinarian about the most appropriate treatment options for your horse.

Figure 3

How do you manage an ulcer prone horse?

Proper management is just as important as medically treating a horse with ulcers.
Management will not heal existing ulcers, but in combination with effective treatment will help to prevent them from recurring. Feeding a diet low in starch with ample forage is ideal. At least 70 – 80% of the daily intake should be in the form of forage, and an ulcer prone horse should have access to forage all the time. Figure 3 shows how the pH of the stomach drops dramatically when the stomach is empty for a long period of time, but consistently stays elevated when given free access to hay. Choosing hay that has an alfalfa component is also helpful, as the calcium in alfalfa
works as a natural antacid and helps to buffer the stomach. Grains should be fed in small amounts, ideally no more than 5 pounds per meal for an average sized horse. Cereal grains that are high in starch will dramatically increase stomach acid production, so high fat/fibre mixes are often a better choice. High fat supplements such as rice bran oil have been shown to protect the stomach and can be a great way to add safe calories to the diet. Ulcer prone horses should be allowed access to ample turnout and should maintain a consistent exercise routine. It is important to ensure they are not being bullied or chased from the feeder in the paddock, as long periods of fasting may result. Changes in the routine (new turnout buddies, different paddock, different feeds etc) should be avoided or made slowly. Often time ulcer prone horses benefit from a few days of treatment before, during or after a stressful event to help prevent flare ups. Because of the common occurrence and economic impact of stomach ulcers, recognizing the signs and appropriately managing ulcer prone horses is extremely important. Please contact your veterinarian for more information if you suspect you may have a horse with stomach ulcers.