In 1999, veterinarians and horsemen welcomed the introduction of omeprazole as a treatment for gastric ulcers in horses. The new animal drug was welcomed as an effective treatment for the estimated 60-90 percent of performance horses that suffer from gastric ulcers – a particularly common problem for on-track Thoroughbreds.
But a common problem in humans and horses on omeprazole is that ulcers often come back when treatment stops. This occurs because the body responds to the withdrawal of omeprazole by overproducing gastric acid. The acid-rebound effect places the individual at higher risk of a relapse.
Ulcers form when the stomach does not have some type of food in it to digest and the gastric acid begins to erode the stomach lining. Omeprazole is a proton-pump inhibitor that completely blocks the production of gastric acid.
Dr. Nanna Luthersson, a private practitioner in Denmark working with researchers from Spain and the United Kingdom, presented research earlier this year at the AAEP Colic Research Symposium showing that ulcers were unlikely to recur in horses fed a low-starch, high-forage diet during and after omeprazole treatment. But three nutritionists familiar with racehorses in the United States say this diet won't work for racing Thoroughbreds.
“It is true that horses that eat a mostly forage diet don't have frequent problems with gastric ulcers, but that situation is moot for racehorses because they simply cannot eat enough forage to meet the energy requirements for maintenance and the work they are required to do,” said Dr. Gary Potter, a Texas A & M University emeritus professor who consults on management of performance horses through his Potter Enterprises.
Dr. Brian Nielsen, professor of equine exercise physiology at Michigan State University, said feeding racehorses a restricted-starch, forage-based diet may work for Standardbreds, but he is doubtful it would provide Thoroughbreds ample fuel to sustain their high-intensity performance that requires more glycogen and blood glucose.
“There is work from Sweden conducted by Anna Jansson of Uppsala University that has shown trotting horses can compete reasonably well on an all-forage diet. But there is strong belief that a diet relatively high in soluble carbohydrates is necessary for the kind of work required of a Thoroughbred racehorse,” he said.
“I suspect that it might be possible if they were on some very lush, young hay that is high in soluble carbohydrates, but I don't think that [research] work has been done. If you think about it, in the springtime horses can develop laminitis on lush pasture due to the soluble carbohydrates—the same as some horses would do with a grain overload. Hence, it likely is possible to be able to provide enough of the necessary carbohydrates when feeding a forage like that, but that would rarely be done.”
As an alternative to the diet Luthersson advocates for other types of performance horses, Potter urged horsemen to adopt a feeding strategy for racehorses in training that provides high-quality forage following a grain meal that would keep the horse chewing and salivating. Saliva is a natural buffer for gastric acid.
Stronger gastric acid has a pH of 1 to 2; buffered gastric acid would be 6 to 7. A pH of 7 is the standard reading for water and is considered neutral.
Dr. Joe Pagan, president of Kentucky Equine Research in Versailles, Ky., said
Thoroughbred racehorses need starch and sugar to make muscle glycogen, and an all-forage, high-oil diet wouldn't provide the components they need to sustain the level of performance expected of them. Instead of the change in diet, he suggested a change in feeding strategy to reduce the risk of ulcers.
KER has been investigating how different types of feed and the amount fed affect gastric pH, and researchers believe timing of feed relative to exercise makes an important difference.
“Say you feed that racehorse at 4 or 5 o'clock in the afternoon, and then you give it free-choice hay at night,” Pagan said. “If the horse doesn't continue to eat hay all night and you look at that horse's digestive fluid in the morning, it's down around 2, very acidic. If you give that horse feed, and particularly if you put a buffer in that feed, you can get the pH up to 6 or 7 before the horse goes out to gallop in the morning.
“I think that ulcers are generated when those horses go out early to gallop with a stomach full of real strong acid. So strategically trying to reduce the acid load pre-exercise is something you can do.
“From our data, it looks like feed alone—sweet feed, not forage—has a pretty marked effect on gastric pH. So at the very least, I would recommend that trainers feed their horses just one or two pounds of feed about an hour or two before they go out to gallop in the morning.”
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