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Equine Gastric Ulcers: Causes, Treatment, Prevention and the Role of Nutrition

Updated: Feb 15

Gastric ulcers is a condition where lesions form in the stomach lining. This condition is becoming increasingly common in horses. In fact, research has shown that 90% of racehorses, 66 to 93% of endurance horses, 58% of sport horses and 11% of leisure horses suffer from gastric ulcers 1. Ulcers in the stomach are painful and have an effect on the horse's health, well-being and their performances.

Photo digestive system horse

The Digestive System and the Stomach

The horse's digestive system can be divided into two parts. The stomach belongs to the first part. In comparison to the other organs of the digestive system, the horse's stomach is small with a maximum capacity of around 8 to 15 litres 2,3. When the stomach is about two-thirds full, it is emptied, regardless of how long the feed has been in the stomach 2. As a result, undigested feed can enter the intestines after ingestion of large portions of feed. This is why horses naturally, frequently eat small portions throughout the day.

Like the digestive system, the stomach also consists of two parts: the non-glandular part and the glandular part 4. Both parts are covered with mucosa. The glandular part consists of glands which are responsible for the production of gastric acid 5. Therefore, this part of the stomach also contains a thicker mucosal layer that protects the stomach wall against the acidity of gastric acid. The non-glandular part lacks a protective mucus layer and is only covered by a thin layer of cells 4. Therefore, this part of the stomach is not protected against the acidity of gastric acid.

The Occurrence of Gastric Ulcers

Horses constantly produce gastric acid, which is required to digest food, even when the stomach is empty 6. The pH in the stomach decreases due to the production of gastric acid, creating an acidic environment. Saliva is produced when horses chew on feed which contains the compound sodium bicarbonate that has a buffering effect on gastric acid. Therefore, it neutralises the pH reducing the acidity in the stomach 7. Roughage also functions as a buffer and is able to absorb excess gastric acid, unlike concentrates which only increase acidity due to digestion 7,8.

If the acid is not properly buffered or absorbed, excess acid can result in lesions in the non-glandular region of the stomach 9. Because the non-glandular region lacks a protective surface against gastric acid, gastric ulcers are commonly found in this area of the stomach. Although, more often horses are diagnosed with gastric ulcers in the glandular region. The definitive cause of this is still unknown, but research suggests that gastric ulcers in this area are caused due to a reduction of the stomach wall's defence mechanism 10.

Due to the continued acidity in the stomach, the affected tissue is unable to heal by itself. Therefore, if the environment remains acidic, chances are that multiple ulcers will develop and will become progressively worse if not treated medically 4. A scoring system has been developed to assess the severity of ulcers that are present in the stomach. The system assigns a score ranging from 0 to 4, with a score of zero indicating minimal damage and lesions and a score of four indicating severe lesions and damage (table 1).

Table 1 To establish a treatment plan, a scoring system is used that looks at the number and severity of peptic ulcers (MacAllistar et al., 1997).


Description of Severity of Injury


The epithelium is intact and there is no hyperkeratosis (thickening of the surface of the mucosa)


The mucosa is intact but hyperkeratosis is visible


Small and single lesions are visible in the mucosa


Large single or multiple superficial lesions are visible


Extensive formation of lesions with areas where obvious deep ulcers are visible

Symptoms, Diagnosis and Treatment of Gastric Ulcers

Symptoms of gastric ulcers can be difficult to recognise and vary per individual horse. The most common symptoms include yawning, deteriorated coat quality, resistance to girthing, decreased appetite, reduced performance, weight loss, change in behaviour, acute colic and recurrent colic 11. Gastric ulcers are also often associated with behaviours like wind-sucking. However, It is possible for a horse to have gastric ulcers without displaying any obvious symptoms 4.

Therefore, if gastric ulcers are suspected, veterinarians will diagnose gastric ulcers by performing a gastric endoscopy using an endoscope to examine the stomach lining and interior. During the endoscopy, the amount, location and severity of the gastric ulcers are examined.

In recent years, several studies have been conducted to study the effectiveness of alternative diagnostic methods. Results from a recent study have linked the development of gastric ulcers to specific measurable components in the horse's saliva 12. Analysing these components in saliva appears to be a potential alternative method for diagnosing gastric ulcers in horses.

After assessing the number and severity of gastric ulcers, a treatment plan is created. The main aim of treatment is to reduce the ulcers, pain and symptoms, promote healing of the gastric mucosa and prevent recurrence of gastric ulcers 4. This is achieved by using medication that suppresses the secretion of gastric acid, thereby neutralising the pH in the stomach and creating an environment in which the ulcers can heal. The most commonly used medications for gastric ulcers are omeprazole and sucralfate, the latter of which is mainly used for ulcers in the glandular part of the stomach 13. In addition to the treatment, it is important to adjust the horse's management and feeding scheme to prevent the ulcers from recurring 14.

Preventive Management Measures.

To support the healing process and treatment or to prevent gastric ulcers, it is important to assess the horse's current management and implement adjustments if necessary.

As previously discussed, horses naturally consume small meals throughout the day, which prevents their stomach from being empty for extended periods of time. Grazing horses with access to roughage all day therefore have a lower risk of the development of gastric ulcers. Because horses graze constantly, they continuously produce saliva which buffers gastric acid 15. If it's not possible to feed small portions throughout the day, feeding sufficient amounts of roughage at least three or four times daily will also be acceptable 16. Providing frequent small portions of feed lowers the risk of the development of gastric ulcers. Feeding several smaller portions of concentrates also has a beneficial effect on the stomach. Ingesting large amounts of concentrates increases the acidity in the stomach and increases the risk of gastric ulcers 14.

Stress affects the digestive system, the stomach and the development of gastric ulcers 7. Therefore, it is important to make sure the horse experiences as little stress as possible. This includes providing the horse with sufficient food, water and grazing at all times.

Research suggests that exercise increases the risk of gastric ulcers. During exercise, the volume of the stomach decreases and the pressure in the abdomen increases 17. When the stomach contracts during exercise, gastric acid reaches the non-glandular region. In addition, during exercise, the pH decreases and becomes more acidic 15. Feeding a small portion of roughage before exercise reduces the risk of gastric ulcers due to the buffering effect of roughage and its ability to neutralise gastric acid before intense activity 18.

Nutrition for Prevention

Gastric ulcers are often related and caused by an imbalance in nutrition. Therefore, it is important to regularly evaluate and adjust the diet in addition to proper management.

It takes a horse much longer to chew a kilogram of roughage in comparison to a kilogram of concentrates. Therefore, chewing on roughage will increase the production of saliva containing the buffering component 15,19. As mentioned earlier, roughage absorbs excess gastric acid making roughage essential for recovery but also prevention of gastric ulcers. Horses having access to sufficient amounts of roughage throughout the day are therefore less likely to get gastric ulcers, as they are constantly chewing and producing continuous saliva and neutralising gastric acid 20.

Concentrates are often supplemented to provide a balanced diet containing all the necessary nutrients. However, a diet containing an excessive amount of concentrates can increase the risk of gastric ulcers. As mentioned, the horse produces less saliva when digesting concentrate feed due to reduced chewing motions 15. Therefore the buffering effect of the saliva decreases. Insufficient roughage intake (less than 1% of the body weight of the horse in dry matter), coupled with excessive concentrate feed, increases the risk of gastric ulcers in horses 21. Ideally, 75% of the diet should consist of roughage, especially when a horse is prone to gastric ulcers 15. Instead of supplementing the diet with concentrates, the diet can be supplemented with Linseed Oil to provide sufficient amounts of energy. Linseed Oil is a plant-based oil and contains fatty acids that provide the horse a long-term energy source without the addition of excess starch and sugar.

Feeding multiple types of roughage has been shown to positively impact the horse's stomach as it mimics their natural diet in the wild. Offering multiple types of roughage to horses increases grazing behaviour and eating time 22.

In addition, the buffering effect of roughage also varies per species. Alfalfa's structure requires horses to chew more and it contains higher levels of calcium and proteins which act as a buffer 23.

The addition of buffering supplements provides digestive and in particular gastric support. By adding ingredients such as Calcium carbonate, gastric acid is neutralized therefore supporting the stomach and reducing the risk of development of gastric ulcers 24,25. Synovium Gastrosafe contains Calcium Carbonate and Magnesium Hydroxide, both of which have a buffering effect. Synovium Gastrosafe is therefore an ideal supplement for horses prone to gastric ulcers and can be used as a preventative supplement.

In summary, nutrition and management of the horse have an effect on the development of gastric ulcers. Through proper nutrition and management, gastric ulcers can be prevented and will provides support during treatment of gastric ulcers.


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