Nutrition-Responsive Diseases in Horses: Equine Gastric Ulcer Syndrome

Nutrition-responsive diseases are those that have nutrition as an important part of their cause or treatment. In this post we’ll discuss the causes of Equine Gastric Ulcer Syndrome (EGUS) as well as how we can use nutrition to manage this condition.

Causes

EGUS is the ulceration of the oesophagus, stomach and/or the small intestine that results in erosion of the mucosal surfaces of these regions. Hydrochloric acid is the gastric acid that is normally found in the stomach. It is secreted by parietal cells from the glandular regions of the stomach, which are in the ventral regions of the organ. The role of hydrochloric acid in the stomach is to denature proteins, activate enzymes, kill pathogenic bacteria and facilitate mineral absorption. Because horses have adapted to grazing, their stomachs constantly secrete this acid regardless of whether or not they are eating.

EGUS is most common in performance horses and it is estimated that 50-80% of horses in work are affected by this syndrome.

The reflux of gastric acid into higher parts of the stomach seems to increase the incidence of EGUS. Prolonged periods without feed or milk may cause this because the feed absorbs the acid and prevents it from splashing around in the stomach. Exercise may also cause EGUS because the stomach becomes compressed during exercise which forces the acid into the dorsal non-glandular regions of the stomach. Exercise also causes the acid to splash. In addition, delayed gastric emptying may also cause the gastric acid to reflux into higher parts of the stomach.

EGUS is also caused by the breakdown of protective mucous barriers in the stomach. This may be due to the use of certain drugs such as anti-inflammatories as well as infection.

Nutritional Management

Long stem roughage that has long enough fibres to stimulate chewing which causes in increased salivation in horses. Saliva includes bicarbonate which acts as a buffer in the stomach and helps to reduce acidity. The roughage also floats on the top of the stomach contents and acts as a “cap” to reduce splashing.

High grain diets increase the risk of developing EGUS and so should be avoided in susceptible horses. A diet high in grains does not promote chewing and so there is less saliva production and less buffering in the stomach. The small dense particles of grain also increase the production of gastric acid and do not float on top of the stomach contents.

Thus, horses susceptible to developing EGUS should be fed a diet high in fibre and low in grains to reduce this risk. Grains may be substituted with fats which are energy dense and are relatively safe. Long periods without feed should also be avoided as well as exercise on an empty stomach. A small meal of roughage before exercise may reduce the risk.

Other methods of preventing EGUS include feeding Lucerne which may help to buffer the acids. Gut protectants, including psyllium, whey and slippery elm may help to “line” the surface of the stomach. However, some of these ingredients may not have much evidence supporting their use in preventing EGUS.

Drugs can also be administered to reduce the production of gastric acid in order to allow the ulcer to heal. These include Omeprazole which acts to block the proton pump in the stomach, Ranitidine which blocks H2 receptors, and Bicarbonate which is an antacid.

That's all for now, in the next post we'll take a look at  "Tying Up" in horses. See you then :)