Equine gastric ulcer syndrome

Equine gastric ulceration syndrome (EGUS) is a common condition seen in many types of horses, but is often missed as the cause of a variety problems, including reduced body condition, changes in appetite, and behavioural and exercise-related issues. EGUS has many causes and can be complicated in nature, so if you think you horse may be suffering from gastric ulcers, call your vet immediately.

EGUS describes the development of ulcers on the inner wall of the stomach caused by exposure to excessive amounts of acids produced by the stomach. As a general rule the horses stomach acids are neutralised by a constant supply of saliva while the horse eats/grazes, preventing the development of ulcers, however under certain conditions, the horse may not produce enough saliva to neutralise these stomach acids which can lead to EGUS.
The severity of gastric ulceration ranges from minimal inflammation of the stomach lining to severe ulceration and bleeding of the stomach lining. In extreme cases the stomach can perforate which can lead to sudden death.
A grading system has been implemented to help classify the severity of EGUS:

  • Grade 0 = intact stomach lining; no appearance of reddening.
  • Grade 1 = intact stomach lining; areas of reddening.
  • Grade 2 = small single or multiple ulcers on stomach lining.
  • Gade 3 = large single or multiple ulcers on stomach lining.
  • Grade 4 = extensive/deep ulcers on stomach lining.

There are two types of gastric ulcer:

  • Squamous ulceration ulcers occur in the upper section (often near the junction between the squamous and glandular tissues) of the stomach as a result of overexposure to acid secretions.
  • Glandular ulceration ulcers occur in the lower section of the stomach where the protective mucus layer overlying the tissue is undermined, e.g. due to side-effects of certain medications, chronic stress and potentially bacterial infections.

EGUS can affect any type of horse, from pony to performance horse. There are a number of risk factors which can lead to the formation of gastric ulcers including, diet, intensive exercise, physical stress/illness, psychological stress and medication, although EGUS can affect horses even in the absence of these factors. Foals are particularly at risk due to the delicacy of the stomach lining at this young age; they also produce high amounts of gastric acid from the first few days of life making them at higher risk of developing EGUS.


The stomach continually produces acids to cope with the continuous trickle of feed horses consume, in turn these acids are neutralised by the saliva produced while eating and trapped within food. Feed in the horse’s stomach forms distinct layers – very acidic fluid and small food particles sit at the bottom in the glandular layer, higher up in the squamous layer the fluid is almost neutral with large food particles, particularly roughage.
When a horse experiences prolonged periods of fasting/starvation, excessive amounts of acids build up causing ulceration. High grain/low roughage diets are also thought to contribute to EGUS as grain requires less chewing which in turn stimulates less saliva. A predominantly grain diet also upsets the normal layering within the stomach. Ulcers can develop within a 24-48 hour period if a horse is unable to eat.

Intense exercise

During exercise blood flow to the stomach is reduced and the pressure in the abdomen is increased which in turn pushes the accumulated acids up into the sensitive portion of the stomach which can cause squamous ulceration.

Physical stress/illness

E.g. shock, infection, parasites, traumatic injury, transportation, stable confinement – these may cause ulcers due to restricted blood flow to the stomach and increased acid production.

Psychological stress

Stressful situations may affect a horses feed intake which leads to reduced saliva production and consequently excess amounts of acids in the stomach; increased acid production also occurs during stress.


some long-term medications or drug overdosage, particularly of anti-inflammatory drugs, e.g. phenylbutazone/equipalazone (bute), can cause restricted blood supply to the stomach which can lead to glandular ulceration.

Many horses will show no signs of suffering from EGUS, however they may show non-specific signs, including poor appetite, slowed eating activity, rough hair coat, weight loss, poor performance, poor condition, colic, changes in behaviour, pain on girth tightening, teeth grinding, difficulty swallowing and excessive salivation. Foals on the other hand will show more obvious signs, most commonly diarrhoea, but also excess salivation, teeth grinding, colic and excessive periods of recumbency.
If you think your horse might be suffering from EGUS, call your vet immediately. Your vet will be able to investigate further with the use of an endoscope to look inside your horses stomach. The procedure is relatively simple and painless and your vet will be able to give you an accurate diagnosis.

Yes, EGUS can be treated simply and effectively.
Initially your vet will ensure your horse’s diet is suitable and discuss any improvements necessary. Other factors to consider are to avoid stress, such as prolonged stabling or long journeys. Your vet may also prescribe some acid inhibitor drugs to help your horses recovery. This usually comes in an oral paste that is given over a 28 day period.
Ulcers can take between 2-4 weeks to heal completely, although severe cases can take longer.

As with most equine conditions, prevention is the name of the game. Feed your horse as naturally as possible allowing daily turnout, ad lib hay and hard feed fed little and often – avoid high grain/low roughage diets.
Avoid stressful situations and regulate your horses exercise – do not over-exercise an unfit horse. Other strategies to reduce stress, such as the use of stable and box mirros can be useful. If  your horse is on long-term medication that could be the cause, you will need to review this treatment with your vet.