Gastric Ulcer In Foals

Gastric ulcers don't just affect adult horses. An estimated 25% - 50% of foals are susceptible to developing gastric ulcers, with a small percentage of foals developing more serious, perforating ulcers. 

Just like an adult horse, the foal’s stomach is divided into two distinct areas – the squamous region, located near the top of the stomach and the glandular region at the bottom. Acid is secreted by cells located in the glandular region. During the first few weeks of life, the cells which line the foal’s stomach undergo many changes including thickening of the lining and increased mucus production to help buffer the glandular region from acid injury. 

Foals are born with a gastric pH of over 4, and by the time the foal is around one week old, their gastric pH is similar to that of adult horses. In healthy foals, the pH of the stomach varies during the course of a day. As a foal nurses, the pH of the stomach increases and as the foal sleeps, the pH drops. 

Why do foals develop gastric ulcers?

Depending on the age of the foal, the risk factors for developing gastric ulcers will vary. In very young foals, acid exposure is unlikely to play a role in the development of ulcers as their gastric pH is usually alkaline. In these animals, it is thought that poor blood supply to the stomach contributes to the development of disease. Foals normally nurse several times an hour and the presence of milk combined with the bicarbonate in saliva that is swallowed during feeding helps to neutralise the stomach acid. 

Lack of milk ingestion is another important risk factor. If the foal is unwell or recumbent (eg. due to limb deformities and musculoskeletal pain) and the frequency of nursing decreases, gastric pH drops rapidly. The administration of non-steroidal anti-inflammatory medications (eg. phenylbutazone/flunixin) can also cause gastric ulceration in foals. Most gastric ulcers in foals are located at the squamous mucosa, whereas foals who have received anti-inflammatory medication or have other  disease often develop glandular ulcers.

In older foals, damage to the pylorus (outflow tract) or duodenum (first part of the small intestine) may prevent the stomach from emptying properly, which leads to the gastric mucosa being exposed to acid for longer periods of time. The stomach of these foals can be so full of fluid that vets sometimes observe gastric fluid leaking from the nostrils due to the backflow of fluid that is unable to leave the stomach. Deep ulcers at the duodenum may cause perforation and death. Foals with gastroduodenal ulcers secondary to outflow obstruction tend to be around 2-6mths old. 

Signs of gastric ulcers in newborn foals include:

• intermittent colic (after suckling/eating)
• restlessness 
• laying down for long periods (sometimes on their back with their legs in the air)
• grinding of teeth
• excessive salivation
• intermittent/interrupted nursing (due to discomfort) 
• diarrhoea
• poor appetite
• spontaneous reflux from the nostrils may be seen on rare occasions 
• sudden death in perforating ulcers 

Signs of gastric ulcers in older foals include all of the above, plus:

• Unthriftiness
• Lethargy
• Pot-bellied appearance
• Small size relative to their peers

Diagnosis:

Most of the signs listed above are non-specific and can be due to other illnesses or diseases. Many foals who are found to have severe gastric ulceration on endoscopy do not show severe clinical signs. Due to the risk of intestinal perforation and death from these “silent” ulcers, it is very important that owners seek veterinary advice as soon as possible if they suspect their foal might be unwell. 

Just like adults, the only way to diagnose gastric ulcers in foals is via gastroscopy. This is carried out in a similar way to adult horses but young, neonatal foals only require a short (2hr) fasting period. Abdominal ultrasound and contrast radiography may also be used to provide additional information and rule out other causes of colic in your foal. 

Treatment:

If disease is found, then treatment should begin. The cornerstone of treatment of gastric ulceration in foals are acid-suppressive drugs such as omeprazole or ranitidine. Omeprazole is a proton-pump inhibitor which stops the acid pumps in the stomach from producing gastric acid. It produces a consistent and profound acid suppressive effect and is the cornerstone for treatment of squamous gastric disease in horses. 

However, it is critical to note that gastric acid is an important defence mechanism and acid suppression may predispose foals to infectious disease. A recent, multicentre study showed that ulcer prophylaxis using omeprazole or ranitidine increased the risk of diarrhoea in hospitalised newborn foals*. For this reason, unless gastric ulceration has been confirmed, prophylactic treatment in foals is not recommended. 

Some foals with severe ulceration or delayed gastric emptying may require additional medications and hospitalisation may be recommended by your veterinarian in these cases. In severe cases, some foals could require life-saving surgery if medical therapy is not successful. 

Prompt veterinary intervention, a diagnosis and appropriate treatment is EXTREMELY IMPORTANT to prevent severe complications. Gastric ulceration in foals is not uncommon and, unfortunately, the clinical signs are often vague and nonspecific. Sometimes the only sign that something isn’t right might be a foal who is “quiet” and owners will frequently report their foal is spending more time sleeping than usual. Foals should be bright, alert and rambunctious. In the author’s experience, a quiet or sleepy foal is a red flag so please contact your vet early! 

References:
* Furr, M. et al. (2012) ‘Treatment with histamine-type 2 receptor antagonists and omeprazole increase the risk of diarrhoea in neonatal foals treated in intensive care units’, Equine Veterinary Journal, 44(SUPPL. 41), pp. 80–86.