More than five years ago I took an interest in ulcers in endurance horses. I started asking questions, checking as many horses as I could, traveling thousands of miles scoping horses that acted like they had ulcers and those that did not, researching treatment and prevention. I wrote several articles for Endurance News (one of which ran in the September 2004 issue; I am repeating here with inserted updates).
Equine gastric ulcer syndrome (EGUS) is increasingly being recognized as a major health problem affecting all equine athletes, including endurance horses. Research has shown that 90% of racehorses and almost 60% of all performance horses are affected by EGUS.
Although EGUS was initially believed to be a health concern primarily affecting racehorses, further studies have confirmed that ulcers affect horses in many other competitive disciplines including eventing, dressage and show jumping.
Extensive studies have been done in many disciplines, but not endurance. Several investigators have looked at endurance horses but not in large numbers. Endurance horses do not gather in large numbers except at rides which is a poor place to perform endoscopy due to the necessity to fast and the advantages of sedation.
In the spring of 2003, a private research entity, with the help of some dedicated AERC members, conducted a study of the incidence of equine gastric ulcer syndrome in endurance horses. As of May 2003, 140 active endurance horses were scoped at 15 clinics in eight states and 50% of them had ulcers. Lack of time and finances have prevented any further studies.
Update: Some of these horses have been followed up. With proper treatment and good management, they have been cured and remain ulcer-free.
EGUS signs and symptoms
Ulcers are the result of excess gastric acid damaging the stomach lining. Unlike the human stomach, which generally produces gastric acid only during meals, the equine stomach secretes acid continuously. Studies have shown that a mature horse will produce approximately 1.5 liters of gastric acid per hour.
onsequently, when there is no food in the horse's stomach to act as a buffer against acidity, excess acid can eat through the protective lining and cause the formation of ulcers.
Studies published by Dr. Al Merritt at the University of Florida demonstrated that when a horse exercises at a trot or gallop, the unprotected part of the stomach is exposed to acid contents, causing ulcer formation.
There are many clinical signs and symptoms associated with EGUS; however, it is important to note that many horses with stomach ulcers do not exhibit any obvious signs. Because the prevalence of stomach ulcers in horses has only been recently understood, ulcer symptoms can go unrecognized by trainers, owners and veterinarians. What complicates the issue is that some horses with severe ulcers may not show any outward signs of illness, while others suffering from mild ulcers may behave very abnormally.
In adult horses, common signs include poor performance, colic, back soreness, attitude changes, resistance to training and poor appetite. Other signs associated with ulcers include poor body condition, a tucked-up appearance, and a poor coat.
Unfortunately, common clinical signs of ulcers are often overlooked or not observed until the problem has progressed. Because of this, stomach ulcers are often undiagnosed or misdiagnosed. While, at this time, definitive EGUS diagnosis can only be made with endoscopy, the clinical signs and symptoms may form the basis for empirical therapy for ulcers after other disorders have been excluded.
Work is being done by Dr. Noah Cohen at Texas A&M School of Veterinary Medicine (and by others) on a blood test -- originally urine but blood appears to be best -- for sucrose levels that shows promise as an alternative diagnostic procedure. When I spoke with Dr. Cohen in 2004, he told me that the test was more than a year away and needed more testing before it would have widespread clinical benefits.
Here is how it would work. Sucrose is a very large molecule that is not absorbed in the normal horse stomach and shows up in the blood and urine of horses with ulcerated stomachs. The urine test is used in humans and dogs in some cases.
Update: As of my last contact with Dr. Cohen, he and his team of researchers are still having trouble with the accuracy of the test.
What causes ulcer formation?
There are several factors that predispose a horse to EGUS. A grain-heavy diet and infrequent grazing or reduced hay intake can lead to stomach ulcers within hours to days. Performance horses often go without feed several hours of each day during training, permitting acid build-up within the stomach and causing damage to the stomach lining.
Prolonged stabling or time spent in stalls, coupled with limited turn-out, can also contribute to ulcers. Extended periods of inactivity or strict confinement results in delayed emptying of stomach contents, conditions that are favorable to ulcer development.
On the opposite end of the spectrum, intense exercise or rigorous training actually increases acid production in the horse's stomach and reduces blood flow to the stomach. Consequently, strenuous exercise can be just as likely to result in stomach ulcers as inactivity.
Other factors such as shipping, frequent competition, unfamiliar surroundings and the use of analgesic anti-inflammatories, such as phenylbutazone and flunixin meglumine, have also been shown to contribute to equine stomach ulcers.
Where to start?
Confirming or ruling out EGUS in your horse is where you start. Endoscopes long enough to adequately examine a horses stomach are few and far between. Universities have them and some of the more progressive equine practices do also. If your veterinarian does not have one you can be referred to someone who does.
If your horse does have ulcers then the only course of action is to remove the source of stress (i.e., training, competition, etc.) until treatment is completed and then embark on rigorous preventive measures before resuming and continue during training and competition.
Update: Recent studies in humans have shown that the long-term use of omeprazole interferes with the absorption of some electrolytes. If this also applies to horses, which I believe it does, then the use of omeprazole in endurance horses is the wrong choice of a prevention program. Good management is still the best option.
