Equine gastric ulcer syndrome (EGUS) is a health problem affecting many horses. EGUS can be responsible for a wide range of clinical signs including poor performance, behavioural changes (mainly being moody and touchy), discomfort on girth tightening, decreased appetite, mild weight loss, dull coat, crib biting, lying down more than usual and mild/recurrent colic. Horses can even have potentially serious gastric ulcers without showing anything at all!
Which horses are at risk?
Any horse at any age can be affected. Studies have shown that it is a very common problem with percentages of occurrence ranging between groups of horses: about 35% of pleasure horses, 60% of performance horses and 90% of racehorses have been found to have ulcers. Foals are at a particularly high risk from EGUS and if young foals undergo treatment for any other disease, it is wise to start preventative treatment for ulcers as well.
Why do horses get gastric ulcers?
To answer this question you must first have some understanding of the basic anatomy of the horse’s stomach. The top part of the stomach is lined by ‘squamous epithelium’ and the bottom half by ‘glandular epithelium’. The squamous part is resistant against mechanical stress (roughage scraping past it) but easily damaged by acid secretions which after prolonged exposure causes ulceration. The glandular part is able to produce hydrochloric acid which is vital for the digestion of food. To withstand the acid exposure it also produces a protective mucus layer with bicarbonate which works as a buffer. Still, inflammation and ulceration of this part is possible as well but is less common and more difficult to treat.
The contents of a normal horse’s stomach is layered; roughage swallowed enters the stomach and forms a dense fibrous mat which helps protect the squamous part against acid exposure. It gets mixed slowly with acid turning the contents into an acidic soup at the lowest part of the stomach.
All the factors that contribute towards ulceration are not fully understood but some risk factors have been identified;
Training and exercise – when exercising, the movement and increased pressure in the abdomen results in acid splashing up onto the squamous lining of the stomach. At the same time, the blood flow to the stomach decreases resulting in reduced capacity of the mucosa to deal with the effects of acid exposure.
Diet – horses are trickle feeders taking in little and often rather than eating large meals and living on stalky roughage only. A prolonged reduction in roughage intake and therefore saliva production can lead to increased acidity of the stomach contents and loss of the protective fibrous mat. When horses are starved ulcers can form relatively rapidly. Concentrate feeds with high carbohydrate levels make the stomach more acidic as well due to the production of volatile fatty acids.
Physical stress and illness – this might include transportation or stable confinement. Horses that have had surgery or other treatment are at greater risk. The mechanisms behind this are incompletely understood but include reduced blood flow and local immunity in the stomach.
Medication – historically being blamed for development of ulcers, NSAIDs (e.g. ‘bute’) at normal doses are NOT associated with EGUS. Used at very high doses for a prolonged period of time or combined with steroids they are a risk factor however.
Bacteria – in people bacteria play an important role in gastric ulceration (Helicobacter Pylori) but in horses the significance is still unclear. In some cases in horses antibiotics are needed to heal persistent ulcers. This is more common in inflammation or ulceration of the glandular mucosa.
Diagnosing gastric ulcers.
The gold standard for diagnosing EGUS is via gastroscopy. A 3+ m. long endoscope is passed via the nose and esophagus (food pipe) into the stomach. After inflating the stomach with air the mucosa can be fully evaluated. Before scoping a horse MUST be completely starved for about 16 hours (no more than 6 hours in young foals). Water should be allowed up to 2 hours before scoping. Mild sedation is usually necessary.
Can ulcers be treated?
The good news is that EGUS is a treatable condition in most cases. A class of drugs called ‘proton pump inhibitors’ of which omeprazole is the only one licensed for use in horses (the active substance in Gastrogard and Ulcergold) very effectively reduces the production of acid in the stomach. In 90% of cases with predominantly squamous ulceration omeprazole is curative after 4 weeks treatment. It is very important however that the horse’s management and feeding practices are looked at to ascertain what can be done to decrease the chances of recurrence of the problem.
There a number of dietary supplements (antacids = acid buffers) that can assist in the management of cases where dietary and management adjustments are not sufficient.
Glandular inflammation/ulceration can be much harder to control, sometimes they require longer periods of treatment with a low dose of omeprazole, a prolonged course of antibiotics or medication to protect the stomach lining (sucralfate).
Dietary management is critical for successful treatment and prevention of gastric ulceration in horses. Free access to good quality forage helps maintain the normal layering of stomach contents as discussed before. In fact evidence shows that forage feeding intervals of greater that six hours are the biggest dietary risk factor for ulceration of the squamous mucosa. Feeding forage should be encouraged right up to the onset of exercise to help prevent acid coming into contact with the squamous mucosa of the stomach. There is currently no evidence that there is a difference between feeding hay or haylage in occurrence of ulceration. Whilst it is generally assumed that grazing reduces the risk of gastric ulceration some individuals at grass have been found to have severe squamous mucosal and/or pyloric ulceration, so this relationship is not totally clear and might depend on factors such as simple sugar content of the grass. Associations between cereal/high carbohydrate feeding and ulceration of the gastric squamous mucosa are well recognised with studies showing that feeding more than 1g starch per kg bodyweight per meal (1-2kg concentrates or cereal for a 500kg horse) more than doubled the risk of having squamous ulcers. It is thought that feeding dietary oils can be beneficial and have a protective effect on the stomach lining, particularly of the glandular mucosa. The way this works is probably because oil provides the substrate for prostaglandin synthesis which increases the local defenses of the mucosa or by binding potentially harmful short chain fatty acids.
On the basis of the above information we have provided some management guidelines:
- Turn out as much as possible for grazing.
- Give hay/haylage (ad-lib or at least at less than 6 hourly intervals) whilst in the stable. If you have concerns re putting on weight then use a small holed net or double net to slow the horse down.
- Add corn oil to feed. Give up to approx. 250ml/day total. This should be divided into several small feeds. Please Note: corn oil should be gradually introduced as it may take time to get used to the taste. Alternatively you could feed a product which has the oil already incorporated in it such as Dengie ‘Alfa-A Oil’.
- Prior to ridden exercise you could give a small amount of fibrous feed (eg Alfa A or Dengie Hifi). This is thought to provide a protective layer over the stomach contents and prevent acid from splashing up onto the squamous mucosa.
- A gastric supplement such as Pool House Equine Clinic EGUS Supplement or ProNutrin is recommended in most cases. This can be obtained through your own veterinary surgeon.
Please phone our practice for further information about the gastroscopy clinic.