Loafing in a stall, an hour or so of work a day, a weekend trip to a show—that hardly seems like a high-stress life. But for horses, whose natural lifestyle consists of grassy fields all day, it may be stressful enough to cause stomach ulcers.
The problem was literally hidden until the late 1980s, when new technology—the gastric endoscope—allowed veterinarians to peer directly into the horse’s stomach. Since then studies have shown that 90 percent of racehorses and 60 percent of show horses suffer from these stomach lesions. Even horses that lead less pressured lives get ulcers.
Ulcers have been implicated in problems ranging from poor performance to colic—but, fortunately, there have been great strides in understanding and treating this condition. Here’s an overview of the latest information from veterinary researchers around the country.
Gastric ulcers form when acidic digestive juices damage the wall of the stomach. In humans a bacterial infection is often the trigger, but so far there’s no evidence of this in horses. Instead, equine stomach ulcers are set off by people—specifically, by a conflict between the lifestyles people dictate for horses and the way the equine digestive system works.
Horses are grazers. Left to their own devices, they nibble all day. To process the steady intake, a horse’s stomach secretes acid continuously. As long as the horse is grazing, this isn’t a problem. The grass (or hay) reaches the stomach mixed with lots of saliva, which contains sodium bicarbonate to buffer the acid.
The picture changes when the horse stops grazing. Without a steady stream of food and saliva, acid levels begin to rise within minutes. And the horse’s stomach isn’t designed to deal with this increased acidity. While your stomach has a protective lining of mucus, the horse has this protection only in the lower half of his stomach. The unprotected upper half is where most adult horses get ulcers.
Some horses seem to be more likely to get ulcers than others, and researchers don’t have all the answers as to why. But studies led by Michael J. Murray at the Virginia-Maryland College of Veterinary Medicine and by other researchers have pinpointed the following risk factors.
• Limited pasture or forage: The less access a horse has to pasture or free-choice hay, the more likely his stomach will be empty and thus more prone to ulcers. Horses on pasture rarely get ulcers.
• Big grain rations: When a horse gets big rations of concentrates—grain or pellets—two or three times a day, he’s less likely to nibble forage between feedings. In addition, some research suggests that carb-rich feeds like grain can increase stomach acidity.
• Intense exercise: Studies show a direct link between exercise levels and ulcer risk. The link is partly related to diet—horses that work hard also tend to be stabled and to get lots of grain. But exercise also diverts blood flow from the stomach. In addition, researchers at the University of Florida have found that acidity rises and the horse’s stomach contracts during exercise, increasing the likelihood that acid will contact the unprotected upper walls.