Gastric ulcers are common in horses and foals worldwide, and the term equine gastric ulcer syndrome (EGUS) was introduced in 1999 to describe a range of inflammatory changes that affect the bottom of the oesophagus, the non-glandular stomach (referred to as equine squamous gastric disease), the glandular stomach (equine glandular gastric disease), and the part of the duodenum next to the stomach.
Did you know?
The prevalence of EGUS in newborn foals is estimated to be 25%–50%, and foals have a high risk of developing perforating peptic ulcers until they are several weeks old because their stomach lining is not developed to full thickness at birth.
Squamous vs glandular ulcers
Research indicates that approximately 80% of ulcers are found in the non-glandular squamous mucosa of the stomach (squamous ulcers). On the other hand, approximately 20% of ulcers can be found in the glandular region of the stomach (glandular ulcers).
Did you know?
The prevalence of EGUS in racehorses in active training and racing has been estimated to be at least 90%, whereas in nonracing performance disciplines, the prevalence varies from 40% to 60%.
Duodenal ulceration
Duodenal ulceration in adult horses and foals is considered part of EGUS as it is believed to be caused by gastric acid. Duodenal ulceration, perforation (rupture), or stricture (narrowing due to inflammation) can occur.
Aetiology
The stomach of the horse is relatively smaller in comparison to other species. As a result, horses cannot handle large amounts of food; they are built to graze and eat frequent, small portions of feed for extended periods. In a natural grazing situation, a steady acid flow is required for digestion. Hence, a horse’s stomach produces acid twenty-four hours a day, seven days a week – up to 35 litres of acidic fluid per day, even when not eating. In a natural, high-roughage diet, the acid is buffered by both feed and saliva, but when horses are fed in meals, fed concentrate, exposed to stressors and worked hard, the balance is disrupted, and the acid is no longer neutralised adequately.
Equine squamous gastric ulcer disease is associated with repeated direct inflammation and erosion by the extremely low pH stomach acid typically found in the glandular region of the stomach. Pressure increases inside the abdomen (usually associated with exercise), collapsing the stomach and forcing the acid gastric contents upward (acid splash) into the squamous region, especially in a horse exercising on a relatively empty stomach. Highly acidic contents of the glandular part of the stomach come in contact with the non-glandular squamous mucosa during intense exercise, causing inflammation and, potentially, erosions and ulceration to varying extents.
Dietary factors also play a role in the development of EGUS. Diets high in concentrates and low in roughage (hay) generate high amounts of short-chain fatty acids (SCFAs; acetic, butyric, and propionic acids) due to the fermentation of sugars. SCFAs are absorbed by non-glandular mucosal cells, making the cells more acidic and leading to eventual ulceration.
NOTE: Not all concentrates are created equal. Lower starch and sugar concentrates are less of an issue for ulcers, than high sugar, high starch formulations.
The causes of ulcers in the stomach’s glandular mucosa (equine glandular gastric disease) are less certain. Factors proposed to contribute to spontaneous equine glandular gastric disease include the breakdown of mucosal defences, bacterial colonisation, environmental and psychological stress, and more general inflammation.
Risk factors
The risk factors for equine gastric ulcer syndrome include:
- Involvement in performance disciplines
- High-concentrate diets
- Feeding in ‘meals’
- Limited access to forage
- Environmental stress (paddock vs time in the stable)
- Stress due to travel or management changes
- Illness
- Chronic anti-inflammatory use
Clinical findings
Foals
Foals with gastric ulcers are often two to six months of age, and EGUS in foals has been divided into four clinical syndromes:
- Subclinical (no apparent clinical signs)
- Clinical (with clinical signs)
- Perforating
- Gastric outflow obstruction.
Most foals have no or only vague clinical signs. However, when gastric ulcers become widespread and severe, classic clinical signs in foals include lethargy, colic, a dull coat, poor weight gain, diarrhoea, inadequate or interrupted nursing, lying flat, grinding teeth, hypersalivation, frothing or drooling of milk from the mouth, and tongue rolling.
Importantly, when a foal has clinical signs, the ulcers are typically severe and should be evaluated and treated immediately. Complications related to gastric ulcers are most frequent and severe in foals. Sudden gastric perforation without earlier clinical signs can sometimes occur in foals.
Adult horses
Adult horses with EGUS have nonspecific or vague clinical signs, including poor performance, abdominal discomfort (colic), poor appetite, mild weight loss, poor body condition, girthiness, dull coat, and attitude changes. Horses with signs of severe abdominal pain (colic) may have gastric ulcers; however, the ulcers are unlikely to be the main cause of the abdominal pain. No strong correlation between the extent of ulceration and the severity of symptoms has been reported.
Complications related to gastric ulcers are most frequent and severe in foals, but they can also occur in adult horses too. They include delayed stomach emptying, acid reflux and inflammation of the oesophagus, expansion of the oesophagus secondary to chronic acid reflux, and, rarely, perforation. Clinical signs in adult horses with equine glandular gastric disease are less known; they are thought to be similar to horses with equine squamous gastric ulcer disease.
Diagnosis
Gastroscopy is the only way to diagnose ulcers definitively. This is done on an empty stomach.
Empirical treatment is indicated when gastroscopy is unavailable. A presumptive diagnosis can be reasonably made when clinical signs are reduced or resolved after several days (three to five days) of treatment with an effective medication, such as Omepracote.
Treatment
Most treatment for ulcers centres around the use of medication and supportive care. While healing of gastric ulcer lesions without medication has been observed, if training and the risk factors that have caused EGUS continue, lesions are unlikely to heal.
Supportive care for horses with ulcers involves dietary management, including feeding low-starch concentrate and lucerne to buffer stomach contents, and stress management, ideally through species-specific modifications, such as increased turnout.
Suppression of gastric acidity is the primary objective of medical treatment for gastric ulcers. Currently, the mainstay of treatment is the proton pump inhibitor omeprazole, usually in the form of Omepracote, which reduces acid production in the stomach, allowing ulcers to heal. Omeprazole is approved for a 28-day treatment course for EGUS, primarily squamous gastric ulcer disease; however, treating equine glandular gastric disease may require 45–60 days of treatment. Repeat gastroscopy may be used to guide the duration of treatment.
Sucralfate, as found in products like Ulsanic, is another medical treatment option. Sucralfate binds to the gastric glandular mucosa and may promote healing. However, studies using sucralfate alone have not shown it to be beneficial in treating squamous gastric ulcer disease in horses or foals. When sucralfate is used with an omeprazole paste, it can reduce the severity of equine glandular gastric disease.
Misoprostol, a synthetic prostaglandin analogue, either alone or with sucralfate and omeprazole, has been shown to be effective in treating equine glandular gastric disease.
Another promising pharmacological agent is the S-enantiomer of omeprazole, esomeprazole. Esomeprazole has been shown to treat equine squamous gastric ulcer disease successfully; however, its treatment efficacy for equine glandular gastric disease is not known.
Prognosis
The prognosis for horses affected by gastric ulcers is generally good. Gastric ulcers can be treated and prevented relatively easily. Most squamous ulcers heal within four weeks of treatment, with glandular ulcers often requiring a slightly longer course.
Prevention
The following management techniques may assist in preventing ulcers:
- Feed horses hay 24/7 or on a free-choice basis (pasture). This helps buffer the stomach acid and stimulate saliva production, nature’s best antacid.
- Reduce the amount of grain and concentrates and/or add lucerne to the diet. Discuss any feed changes with your vet so that medical conditions may be considered.
- Avoid or decrease the use of anti-inflammatory drugs.
- Limit stressful situations such as intense training and frequent transporting.
- If horses must be stabled for large parts of the day, allow them to see and socialise with other horses and have access to forage at all times.
Final thoughts
Gastric ulcers are incredibly common in our equine population. If you suspect your horse is suffering from ulcers, contact your vet to discuss the best way forwards.