Gastric Ulcers in Horses
The equine stomach is composed of a nonglandular, or squamous, component as well as a glandular component. The squamous mucosa makes up approximately one-third of the stomach, has no glands, and is typically responsible for mixing food. This portion of the stomach has very little protection from the acidic environment present in the lower portion of the stomach. The glandular portion (lower portion) makes up the remainder of the stomach and contains specialized glands that secrete acid and other substances that breakdown food. The lower portion of the stomach contains numerous protective mechanisms to keep it safe from acid. Although both parts of the stomach can develop ulcers, occurrence in the non-glandular mucosa is more common.
In the wild, horses spend most of their day grazing. As a result, the equine stomach has adapted to constantly secrete acid, which is then buffered by saliva from chewing as well as the feed itself. In some man-made environments, feeding conditions are very different to that in the wild. This results in the stomach remaining empty for prolonged periods of time, exposing the vulnerable squamous mucosa to higher levels of acid. High-grain diets and stressors (such as transport and stall confinement) can also contribute to the development of ulcers.
Long-term administration of medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) can lead to a decrease in protective factors and predispose horses to ulcers predominantly in the glandular mucosa. This class of drugs include common medications such as flunixin meglumine and phenylbutazone.
Definitive diagnosis of gastric ulcers can only be made by direct visualization of ulcers using an endoscope, a technique known as gastroscopy. Although a tentative diagnosis can be made based on clinical signs and, potentially, response to therapy, the location and severity of ulcers cannot be determined with this method. Gastroscopy is a quick and minimally invasive procedure that allows the veterinarian to visualize the upper airway, esophagus, stomach (both glandular and non-glandular portions) and the proximal small intestine.
After assessment of non-glandular ulcers, a numerical grade is assigned which then can be used for comparative evaluation. Grade 0 is typically considered a normal horse with no evidence of ulceration, while a horse with grade 4 ulceration has deep, bleeding ulcers throughout the non-glandular mucosa.
The mainstay of treatment is prolonged suppression of acid, the formation of a protective layer over the ulcerations, and maintaining adequate blood flow to the site of ulceration. Omeprazole is currently the only Food and Drug Administration approved treatment for gastric ulcers, and it works by suppressing acid secretion in the stomach. Although there are many other products currently available, the formulation of this medication makes it the treatment of choice for gastric ulcers in horses.
Another potential treatment for ulcers is sucralfate, which is a gastroprotectant that binds to ulcers and creates a protective barrier, thereby providing immediate (although relatively short-lived) relief. Glandular ulcers may require additional therapy if first line treatment does not result in improvement.
In addition to pharmacologic intervention, management strategies are crucial to the maintenance of an ulcer free horse. By providing free choice access to roughage in the form of grass or hay, large changes in stomach pH can be minimized. Alfalfa hay, which tends to be slightly higher in calcium, can be a good option as its buffering capacity is above that of regular grass hay.
Limiting or controlling stressful conditions plays a major role in the treatment and prevention of gastric ulcers in horses. While there are many supplements on the market that claim to prevent or treat gastric ulcers, they may lack validation and are not considered effective. Although there is a lack of peer-reviewed scientific research regarding most supplements on the market, those containing pectin and/or lecithin may provide the most benefit.
Gastric ulcers in horses can be challenging to identify and, in many cases, challenging to treat. By using medication to modify the acidic stomach environment in combination with management strategies to maintain a more “natural” environment, we can help treat and prevent most ulcers in horses.
Editor’s note: This is an excerpt from Equine Disease Quarterly, Vol. 32, Issue 2, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents. It was written by Nimet S. Browne, DVM, MPH, DACVIM of Hagyrad Equine Medical Institute in Lexington, Kentucky.
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