The horse’s stomach is actually divided into two areas – the squamous upper portion and the glandular lower portion. Both squamous and glandular disease are distinct and completely unrelated in terms of their appearance, risk factors, treatment and management. They both just happen to occur in the horse’s stomach.
The squamous portion is similar to the lining of our mouth. If we add acid to this lining, ulcers develop. Squamous disease is essentially acid getting onto a tissue that’s not designed to be covered by acid, has limited defence mechanisms against acid and where the acid has a corrosive and burning effect.
Glandular disease is less well understood. The glandular lining is used to living in an acid environment (this is the part of the stomach where the acid is produced) and usually has good defence mechanisms against it. However, for reasons we don’t fully understand, these defence mechanisms breakdown leading to disease in this part of the stomach. What we know about squamous disease cannot be extrapolated to glandular disease – they’re entirely different diseases, and we need to treat them as such.
Signs of gastric disease are quite vague and non-specific and may include one or more of the following signs:
Currently, the only way to diagnose gastric disease is via gastroscopy. This is a simple procedure that involves passing a fibreoptic camera into your horse’s stomach to look at the lining of the stomach – where ulcers can develop. It is important that your horse is fasted for the procedure as the stomach needs to be empty for your veterinarian to perform a complete exam.
Many horses owners are reluctant to fast their horse for gastroscopy as they feel this will cause ulcers to develop. This isn’t true as vets scope many horses who have been fasted overnight and have completely normal stomachs.
Technically, this is correct. Medication to suppress acid is the cornerstone for the treatment of both squamous and glandular disease. BUT – every horse is different, every lesion is different and your vet will tailor a specific treatment plan for your horse.
Omeprazole paste is very effective for treating squamous disease but is not very effective for glandular disease. Studies have shown that enteric-coated omeprazole (Gastrozol) is more effective than buffered omeprazole 1 . There is actually no universally effective treatment for glandular disease. The use of unregistered products such as extended-release injectable omeprazole, misoprostol or esomeprazole may be required2.
While omeprazole paste is very effective for squamous disease, it MUST be given first thing in the morning at least 30-60 mins before feeding when the stomach is the emptiest. Omeprazole doesn’t just neutralise acid when it reaches the stomach. It has to leave the stomach and enter the small intestine where it gets absorbed into the bloodstream. From here, it then switches off the ‘pumps’ which produce acid. The presence of large amounts of food in the stomach will actually reduce the effectiveness of omeprazole and could lead to treatment failure. The horse’s stomach is emptiest first thing in the morning and this the ideal time to give omeprazole paste for maximum effectiveness.
Horses exercised on an empty stomach will be at high risk for developing squamous disease. This is because the pH of the stomach reduces to less than 4 when a horse begins trotting and the acid will splash up onto the squamous part of the stomach and cause ulcers. Feeding 2-5L of forage (hay or chaff) before exercise will help form a fibrous ball in the stomach which will help prevent this acid splash. Feeding hay might be better as hay requires more chewing. Chewing produces more saliva which is rich in bicarbonate and can help buffer stomach acid. Feeding also helps maintain blood flow to the stomach which is important in maintaining the ‘protective factors’ (mucus etc) to the glandular portion.
Recent behavioural studies have shown that horses dramatically reduce their feed intake between the hours of 10pm and 6am. During this time, the pH of the stomach drops to below 4 which means that the risk of developing squamous disease in horses who are exercised first thing in the morning on an empty stomach is high. Feeding before riding (see above) will help prevent this acid splash.
One study showed that showjumpers who exercised 6-7 times per week were 3.5x more likely to develop glandular disease compared with horses exercised less 5 days per week 3 . It is thought that exercise diverts blood away from the stomach to the muscles which may impair the stomach’s natural protective mechanisms. Reducing exercise to less than 4-5 days per week or exercise every second day is an important factor to consider when managing/preventing glandular disease. Be sure to provide at least 2-3 complete rest days per week4.