By Julia Shrubb MA VetMB Cert(AVP)EM MRCVS
Ashbrook Equine Hospital.
Equine Gastric Ulcer Syndrome
Equine gastric ulcer syndrome, commonly called “stomach ulcers”, is a syndrome where the stomach lining becomes damaged. Stomach ulcers can affect any horse but are very common in competing horses. Some reports suggest that 2 out of 3 performance horses and over 9 out of 10 racehorses have some degree of gastric ulceration. Not all of these ulcers will be clinically significant i.e. affecting the horse. In order to understand the different types of ulcers and risk factors, we need to look at the anatomy of the equine stomach.
The Equine Stomach
Horses have evolved to be trickle feeders. They eat a roughage diet almost constantly which means the stomach always contains some fibrous food. For this reason, a horse’s stomach (unlike ours) continuously secretes gastric acid whether there is food there or not.
The horse’s stomach also has a very unusual anatomy because it is split into two distinct parts. The margo plicatus is the obvious junction between the top, pale pink, ‘squamous’ part and the bottom, red, ‘glandular’ part. The bottom 2/3rds of the stomach, the glandular part, is similar to our own, with cells secreting gastric acid as well as other factors and mucous. Here the pH can be very low (acidic) and normally the wall (mucosa) is protected by a bicarbonate and mucus barrier.
The top 1/3rd of the stomach is the squamous part. This area has no glands and has very little protection against acid. This is not a problem if the horse is trickle feeding as a fibrous mat forms in the stomach and the pH in the top layers of food is much less acidic than at the bottom. However; if this mat is disrupted, it is not surprising that this unprotected area is so susceptible to acid damage and gastric ulceration.
Risk Factors
Much research has been done on squamous ulcers including risk factors, but in the last few years the importance of glandular ulceration has been realised. Research is ongoing to try and identify the pre-disposing risk factors and treatment approaches for glandular ulceration.
Diet is a key consideration for the risk of squamous gastric ulcers, but is less significant in glandular disease. As previously stated, the horse’s stomach secretes acid continuously whether the horse is eating or not, although recent research suggests this reduces overnight. Gastric acidity is very high in an empty stomach and intermittent feeding has been shown quite clearly to induce ulceration. Roughage not only maintains the fibrous mat and pH layers in the stomach, but also stimulates saliva production which neutralises the gastric acid. High starch (grain) diets also stimulate stomach hormones such as gastrin which encourages further acid release. Unfortunately many competition horses require high starch, reduced roughage diets in order to perform. The lowest incidence of ulcers is seen in horses grazing continuously.
Other risk factors include exercise and mental and physical stress. High speed exercise increases the pressure in the stomach and increases the acidity, as well as physically forcing acid up into the sensitive squamous portion of the stomach. Exercise is not easily avoided in the competition horse(!) but feeding a small amount of roughage (hay or small bowl of chaff) immediately prior to working can help reduce acid injury to the squamous area.
Stress such as box rest, transport and illness have all been shown to increase the risk of ulceration. Even trivial changes in management have been shown to induce ulcers quickly. Unlike other species, such as ourselves and dogs, non-steroidal anti-inflammatory medication (e.g. “bute”) is not strongly linked with gastric ulcers.
Clinical signs
Many horses will have some degree of mild ulceration and not necessarily show any signs. Signs that are seen can be subtle and non-specific.
Signs include:
- Poor appetite / slow eater (squamous ulcers)
- Poor body condition / weight loss (squamous ulcers)
- Attitude changes e.g. depression, aggression, ‘not quite right’
- Decrease or drop in performance
- Abdominal pain e.g. on girth tightening
- Mild recurrent colic
Diagnosis
The only way to definitely diagnose squamous and glandular ulcers is by gastroscopy. This involves passing a three meter endoscope (camera) up the nose and down into the stomach. Horses usually tolerate this very well and just a small amount of sedation is given to help pass the tube. Horses need to be starved for a minimum of 12 hours prior to gastroscopy. Air is put into the stomach to help visualize the mucosa. The squamous part is usually quite easy to see but the glandular part can be a bit more difficult due to the J-shape of the horse’s stomach. Horses can usually travel home and be fed within 30 minutes of the procedure.
Treatment
The aims of treatment are to eliminate clinical signs and prevent ulcers from recurring. This is done by a combination of medical treatment and management changes.
One of the most commonly used treatments is omeprazole (Gastroguard™/Peptizole™). This drug suppresses gastric acid secretion and is very effective in allowing acid-induced squamous ulcers to heal. The paste formulation is pH stabilized and has been specifically developed for horses. Omeprazole is a very safe treatment and can be given whilst horses remain in training.
Other treatments that may be considered, especially in glandular ulceration, include sucralfate, which binds to the ulcerated glandular mucosa. Treatment may be required for several weeks or months for glandular disease. Your vet will advise the best course of treatment for you horse depending on the location and type of ulceration.
There are quite a few gastric supplements available. Most of these are based on antacids which neutralise the stomach acid. Unfortunately they are very short acting in the horse but can be beneficial if their use is targeted e.g. immediately before exercise. A pectin-lecithin supplement is also available which helps increase mucous buffering and may be beneficial in glandular ulceration.
Assessing the management and environment of the horse is vital in both treating and preventing gastric ulceration. Roughage (grass/hay/haylage/chaff) is a very important part of the diet and a horse should not go for several hours without access to roughage. A small amount of roughage immediately before exercise can help prevent acid induced squamous ulcers.
Ideally a horse prone to squamous gastric ulcers should be on a limited grain ration but this has to be balanced against requirements for optimum performance. Adding some oil to the diet may be beneficial to the mucosal barrier and help minimise glandular ulceration, as well as reducing the amount of grain needed.
Turnout, enriching the stable environment and looking at ways to minimise travel, exercise and competition stress are also key considerations. It is though that ensuring a competition horse has two to three rest days a week reduces the risk of glandular ulceration.
Summary
Gastric ulceration, in both the squamous and glandular areas, affects many horses, particularly competition horses. Clinical symptoms are subtle and non-specific and some horses will not show any symptoms. Risk factors for squamous disease are well studied and understood allowing management changes to be made. Risk factors for glandular disease are much less understood. Treatment for both squamous and glandular ulceration is usually very effective especially if management changes are concurrently made.
