Stomach ulcers are inflammations of the stomach lining that occur when the protective mucosal layer is damaged.
How does a stomach ulcer develop?
Imagine your horse’s stomach as a kind of pouch holding 8 to 12 liters, where food enters via the esophagus. The lower half is lined with glandular mucosa that produces stomach acid. This acid helps digest the food but also has another important role: to neutralize bacteria and harmful substances ingested with food.
The upper half of the stomach has a different type of lining, which is more vulnerable to acid. In nature, horses eat low-energy, fiber-rich food almost continuously, keeping the stomach filled and buffered. Saliva and food neutralize stomach acid. If there’s not enough intake, the acid becomes too concentrated and can damage the mucosa, causing inflammation. The same happens if a horse eats a large portion of concentrates—less saliva is produced and the stomach fills quickly, allowing acid to splash higher up the stomach wall.
Consequences of stomach ulcers
Stomach ulcers negatively affect the performance of sport horses. In a study on racehorses, ulcers were induced by withholding roughage. Half of the horses received medication to prevent ulcers; the other half did not. Performance tests showed that the untreated horses tired more quickly, had shorter stride lengths, and lower oxygen uptake. According to Linda van den Wollenberg, veterinarian at the Animal Health Service: “This indicates that stomach ulcers impair performance. Also, if ulcers reduce appetite, the horse may not get enough nutrients, further reducing performance. So one effect can lead to the other. Either way, inflammation redirects body resources, and the horse’s health is no longer optimal.”
Symptoms of a stomach ulcer
There are several symptoms that may indicate stomach problems. The challenge is that no single sign confirms it definitively. Some symptoms are vague or even absent. One horse may show more than another. The absence of symptoms does not guarantee there’s no issue. Even if you suspect stomach pain, it can’t be seen or felt from the outside. Only a vet can diagnose ulcers using a gastroscope—a long tube with a camera and light passed through the nose into the stomach. The screen will show whether ulcers are present.
Some symptoms include:
Treating stomach ulcers
If your vet has diagnosed severe stomach ulcers in your horse, treatment with acid blockers is often necessary. Even more important is to evaluate the feeding and management routines to identify the cause. In humans, a specific bacterium can cause ulcers, but this has not yet been confirmed in horses, which is why antibiotics are not the right approach.
Risk factors at a glance
Too little roughage
Unlike humans, horses produce saliva mainly while chewing. Saliva helps neutralise stomach acid. If a horse doesn’t chew enough, it produces less saliva, increasing the risk of ulcers. Providing unlimited roughage allows for sufficient chewing and saliva production. The fibre-rich content also helps buffer stomach acid.
Concentrate feed diet
Horses chew concentrates less thoroughly, resulting in less saliva production. Ingredients like starch and sugar are digested differently than roughage and may contribute to ulcer formation.
Medication
Certain drugs such as painkillers, corticosteroids, and dewormers can impair the protective lining of the stomach, making it more susceptible to acid damage.
Stress
Stress produces chemicals that increase stomach lining sensitivity to acid. Horses feel stress when their basic needs—unlimited roughage, free movement, and social contact—are not met.
Intensive training
Heavy work increases stomach contractions due to the body being in "flight mode". This causes acid to splash onto the unprotected upper stomach. Especially risky is working on an empty stomach, as there is no roughage to buffer the acid.
Preventing stomach ulcers in horses
Management and nutrition play key roles in preventing ulcers. Chewing stimulates saliva, which buffers stomach acid. Ensure your horse has 24/7 access to roughage like hay or grass. If you're worried about weight, choose low-energy hay or use a small-hole hay net or grazing muzzle. Remember, horses don’t sleep through the night like humans and graze 16–18 hours per day in the wild.
Source: Pavo
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