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Gastric ulcers in racehorses: treatment options to try
This common disease in Thoroughbred racehorses hurts performance.
Gastric ulceration is an extremely common ailment in Thoroughbred racehorses and can be a performance-limiting disease. When they're young, most racehorses have normal stomachs, but once they begin training, most will develop ulcers.
Indeed, race training has been shown to increase the prevalence and severity of ulceration, sometimes in as little as three months after being introduced to the racetrack, according to one study. The unique conditions found in a racetrack's backstage environment predispose racing Thoroughbreds to ulcers. Those conditions include the feeding regimen, stresses of confinement and intense training and racing regimens. All have been indicated as factors leading to an increased incidence of gastric ulcers.
"Prevalence of ulceration in Thoroughbred racehorses is very high. In my experience, it's around 85 percent to 90 percent, and probably reaches 100 percent at some point in a horse's career," says Bryan Young, DVM, of Young Equine Services, Cypress, Texas.
Signs of gastric ulceration in adult racehorses include poor eating and body condition, weight loss and, in some instances, poor racing performance.
A few nonpharmacologic treatments can reduce the signs and incidence of gastric ulceration in some racehorses. However, the primary treatment is pharmacologic suppression of gastric acid secretion, most effectively dosed daily.
The importance of diet
The horse is meant to be a continuous feeder, says Young. The roughage it eats helps to buffer low pHs, which begin the ulceration process.
Scott Hay, DVM, notes that the horse's penchant for grazing means it is a constant gastric-acid secretor. "But we want to feed them 'meals,' and necessarily so in some instances," notes Hay, a veterinarian at Teigland, Franklin and Brokken, DVMs, P.A., in Fort Lauderdale, Fla. He says in essence that it would be difficult to keep racehorses at a high level of nutrition without allowing them constant access to roughage, yet that constant feeding may lead to ulcerations.
Horses simply don't get the same benefits from constant grazing as they do when being fed meals of grain, he continues. "That's why people try to keep hay in front of them constantly. If they're being fed grain meals, they don't eat all the time and don't pick and graze as they would do in the wild," he continues. "Having the constant exposure to gastric acid secretion means they're prone to ulcers."
Type of diet and amount of roughage fed may play a role in the induction of ulcers. Feeding hay alone increases postprandial gastrin concentrations, and feeding pellets or grain may result in a larger increase in postprandial serum gastrin, which implies increased gastric acid secretion. Hay and grain contain varying amounts of fermentable carbohydrates, converted by bacteria to volatile fatty acids (VFAs). It has been shown that VFAs at low stomach pH may penetrate the mucosa and cause local acidification, inflammation and ulcers. Adding a good protein source such as alfalfa hay and a higher calcium content to the feed may help buffer stomach acid. Not continuously feeding a horse or depriving it of food for long periods (e.g., 48 hours) also may induce ulcer formation.
Young notes that racehorses need a high-protein feed just as human athletes need a high-caloric intake. He suggests that trainers and owners balance a racehorse's high-protein feed with a lower protein feed that also will help to buffer acidic components. This could include different types of oats, perhaps a pellet for horses that are more susceptible. Young says alfalfa hay has been shown to help in buffering stomachs, not in causing ulceration as had been assumed in the past.
A break in the training regimen
Hard and frequent training may be another reason racehorses are prone to gastric ulcerations. Young notes, "We've seen that ulcerations will heal in a relatively short period of time, 30 days or so, with rest from the racetrack."
Hay recalls working with one filly that was unable to consistently keep weight on. "She didn't eat well at certain times. She was a top-quality horse and raced in stakes company. She wasn't winning, but she was very competitive," he remembers.
"The trainer decided to give her some time off, not only because of her ulcer problem, but also for some foot issues. They assumed she had the ulcer issues, though they were never diagnosed definitely by esophagogastroscopy. But they always assumed she had them by her body weight and eating habits. They turned her out on a farm, treated her with gastric ulcer medication and gave her three months off. And she started to look great."
The horse was put back into training, but her signs returned. Hay administered omeprazole for two months, and she won four stakes races in a row. "She just needed to be kept on medication to compete right, be able to eat constantly, keep her weight on and be at the top of her game," Hay says.
He calls her a poster-horse for treatment of gastric ulcers and how racehorses can be kept performing at top level by taking care of the underlying gastric problem.
At the racetrack, Hay says, veterinarians give medications such as phenylbutazone, flunixin meglumine and nonsteroidal anti-inflammatory drugs (NSAIDs) that tend to reduce horses' defense mechanisms to other diseases and conditions and, thus, predispose them to ulcers. Meanwhile, the objective of pharmacologic treatment of ulcers in racehorses is to make them feel better, eliminate clinical signs, promote healing and prevent recurrence so the horses eat well, maintain good weight and stay competitive.
To decrease gastric acidity, treatment options include H2-receptor antagonists and proton pump inhibitors. The H2-receptor antagonists block the interaction of histamine with H2 receptors on the parietal cell, decreasing hydrochloric acid secretion. They also partially inhibit feed- and pentagastrin-stimulated acid secretion.
Proton pump inhibitors block gastric acid secretion via irreversible inhibition of hydrogen-potassium ATPase, the final enzymatic step in the acid secretory pathway.
Other possible drug therapies include synthetic prostaglandins, mucosal protectants and antacids, the latter of which neutralize stomach acid usually via a mixture of aluminum and magnesium hydroxides. Young also recommends buffering agents, corrective suspensions and various magnesium hydroxide products such as Pepto-Bismol or GastroCote (bismuth subsalicylate). "If given daily, we see at least some cessation of signs. We don't think we're going to cure ulceration with those products, but at least the horse will feel and eat better and, subsequently, will perform better," he notes.
All of that said, however, Young points to omeprazole as the "first line of defense" in his equine practice. "We feel that GastroGard, a proton pump inhibitor, has the best results. Unfortunately, it is expensive. A lot of clients simply cannot afford a daily tube of GastroGard, which can run veterinary bills up to $1,000 per month, just for trying to keep ulceration away."
He also uses compounded omeprazole, but cautions that he doesn't see the same level of results as with the GastroGard. "But we do see some results and some cessation of signs," he says. "And from a financial perspective, our clients like compounded omeprazole more on a daily basis."
If esophagogastroscopy finds significant ulcerations, Young strongly recommends that GastroGard be administered.
Controlling gastric ulcerations in racehorses is a complex process —one that requires reduced training, a change in feeding regimen and perhaps pharmacologic administration.
Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is also an author and editor on nutrition, physiology and veterinary medicine with a background in horses, pets and livestock. Kane is based in Seattle.