By Bonnie S. Barr, VMD, DACVIM
Gastric ulcers are a common medical condition in horses and foals. Numerous publications have identified that up to 60% of show horses have ulcers and up to 90% of racehorses may develop gastric ulcers. The equine stomach holds about 4 gallons and is divided into two distinct parts, the nonglandular portion and the glandular portion. The nonglandular portion covers the upper 1/3 of the equine stomach and is lined by tissue similar to the lining of the esophagus. The glandular portion covers the lower 2/3 of the stomach and is similar to a humanís stomach. Gastric acid is produced by the glandular portion of the stomach but is most harmful to the non-glandular portion because it lacks mechanisms to protect itself from the gastric acid. The glandular portion is protected from gastric acid by several mechanisms including production of an acid-neutralizing buffer, mucous and appropriate blood flow. Simply put, a gastric ulcer is a wound in the lining of the stomach caused by gastric acid. Horses secrete gastric acid constantly, so horses that graze all day are less likely to have gastric ulcers because forages buffer the gastric acid keeping it at a lower level in the stomach. Initially veterinarians thought that the development of gastric ulcers was due to increased gastric acid production and the use of non-steroidal anti-inflammatory drugs, such as bute or banamine. More recently, studies show that ulcer development is more complex and is described as an imbalance between factors that protect the lining of the stomach and factors that can irritate the lining of the stomach, specifically gastric acids.
Several risk factors have been identified that make a horse more prone to the development of gastric ulcers. Horses confined to the stall and fed high grain diets are at a risk for developing gastric ulcers because grain results in the release of a hormone (gastrin) that stimulates the production of gastric acid. Intermittent feeding results in a build-up of gastric acid in the stomach especially during the periods when the horse is not eating. Strenuous exercise can result in gastric ulcers by decreasing the ability of the stomach to empty properly and decreasing the blood flow to the stomach. Non-steroidal anti-inflammatory drugs inhibit several of the bodyís natural protective mechanisms thus making the horse more prone to gastric ulcers. The prevalence of gastric ulcers is higher in show and racehorses due to an inconsistent lifestyle of exercise and stall confinement. A bacterium called Helicobacter pylori
causes gastric ulcers in humans and dogs but the role in horses in unknown.
Clinical signs associated with gastric ulcers are numerous and often vague. Typical symptoms include poor performance, poor hair coat, picky eating, and colic. Oftentimes diagnosis of gastric ulcers can be tricky because the signs can be subtle and easy to misinterpret. Changes in attitude or a decline in body condition could be an indication of gastric ulcers but could also be suggestive of a different medical condition. The gold standard of diagnosis is gastroscopy, which is visualization of the stomach with a 3 meter endoscope. The endoscope is inserted through the nose into the esophagus and then into the stomach. The horse is usually held off of feed for 12 hours and water for 4-6 hours prior to the gastroscopy to allow for thorough visualization of the stomach. If gastroscopy is not available, therapy can be started if gastric ulcers are strongly suspected and improvement suggests that the horse had gastric ulcers.
The primary goal of treatment is to suppress gastric acid. The suppression of acid creates an environment conducive for healing. A lot of products are available for acid suppression. The most commonly used product is omeprazole, which is available under the brand name GastroGard®. This product blocks gastric acid production at the level of the cells in the stomach. GastroGard® is given orally once a day for 28 days and gastric ulcers heal well. The H2 blockers (ranitidine or cimetidine), which block one of the hormones that stimulate gastric acid production, are not as convenient because they have to be given multiple times a day for an extended period. Antacids and gastric protectants can be given but are not as practical or effective. Environmental and dietary management, along with pharmacologic therapy, may be beneficial to facilitate ulcer healing. Management changes include increasing the amount of roughage/forage in the diet, decreasing the amount of grain in the diet and feeding frequent small meals. Turning the horse out on pasture and limiting stress are key management practices for treatment and prevention of gastric ulcers. Those horses that reside inside will benefit from having free choice hay. Research has shown that a lower dose of GastroGard® is effective in prevention of gastric ulcers. Gastric ulcers have a big impact on a horseís performance and overall health, but with appropriate management and treatment gastric ulcers can be prevented.