Gastric Ulcers

What you need to know about this surprisingly common problem.

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.

Inside Story

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.

Risk Factors

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.

• Medication: Nonsteroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone (Bute) can contribute to ulcers, generally when they’re given at high doses or over a long time. The drugs suppress inflammation, but they also suppress natural body chemicals that help protect the stomach from acid.

• Stress: Shipping, mixing with a new group of horses, fighting an illness, and other kinds of physical and environmental stress increase the risk of ulcers. Some horses handle these stresses better than others—in one study, researchers at Purdue University found that nervous horses were more likely to develop ulcers.

Trouble Signs

Ulcers don’t typically produce specific symptoms. Instead, you’ll see general signs—loss of appetite, weight loss, poor coat, a dull attitude, or agitation (a response to pain). Ulcers can also trigger episodes of colic, mild or severe. Some research links ulcers to cribbing. One theory is that horses crib to produce more saliva, to buffer stomach acid.

None of these signs will tell you that a horse has an ulcer, as all could stem from other causes. Your vet will need to scope your horse’s stomach to find out for sure. This means a trip to a clinic that has a gastric endoscope, a 10-foot flexible tube with a light and a tiny video camera at the tip. It’s snaked through the horse’s nose, down his throat, and into his stomach. (A simpler test may be on the way. Veterinarians at Texas A&M University have reported good results in diagnosing equine ulcers by measuring sucrose levels in urine. Similar tests are used for people and dogs.)

The good news is that ulcers are usually treatable with medication, changes in management, or some combination of the two. The bad news is that they’re likely to recur. That means a horse with ulcers may need some permanent lifestyle changes, and perhaps some preventive medication, even after the ulcers heal.


The goal here is to reverse, as far as possible, the risks listed above.

• More forage: Maximize pasture time and offer free-choice hay, to keep some acid-buffering forage in the horse’s stomach. At the University of Tennessee, researchers have found alfalfa hay to be especially good at buffering acid. Free choice alfalfa would be too rich a diet, but including some alfalfa in the total ration could help.

• Less grain: As you increase forage, decrease grain. Divide the horse’s grain ration into three or four small feedings a day, to further shorten the times when his stomach is empty. Some veterinarians suggest replacing part of the grain ration with alfalfa pellets or with a high-fat feed, which may produce less acidity than grain.

• Less work: Time off, or at least cutting back on exercise and training, will give the ulcers a chance to heal.

• Change meds: Talk to your vet about medications that could be contributing to the problem.

• Less stress: Avoid shipping and other stresses, and increase turnout.

Those steps alone may be enough to heal an ulcer. A horse also needs medication for healing to occur.


Most ulcer treatments are designed to either neutralize or block production of the acid that’s causing the problem.

Common antacids, such as magnesium hydroxide, aluminum hydroxide, and calcium carbonate, are neutralizers. They work in horses (although they’re not officially approved for this use), but for practical reasons they’re not widely used. At the University of Florida, researchers have shown that that 240 milliliters (about a cup) of an extra-strength oral antacid such as Maalox Therapeutic Strength will lower a horse’s stomach acid for a few hours. But this whopping dose has to be repeated four times a day to fight ulcers, and not all horses are eager to take it.

Several antacid feed supplements are marketed as ulcer preventives rather than cures. These products are given with feed, so they have their greatest impact when the horse is eating—the time when stomach acidity is at its lowest anyway, thanks to the buffering action of saliva. It’s not clear how much good they do. Vets are also divided over the use of the human ulcer-coating agent sucalfate (Carafate); studies have yet to show it’s helpful for horses.

Drugs that block acid production do work, research shows. They fall into two groups. Those like ranitidine (Zantac in human medicine) block the action of histamine, a body chemical that stimulates acid production in the stomach. As with antacids, the horse needs significantly more than you do. Dosage varies with the case, but the drug is usually given three times a day for three to four weeks.

Omeprazole (GastroGard for horses; Prilosec for people) blocks the mechanism through which the stomach produces acid. Its effects last longer than the other drugs, so it can be given once a day. Horses can often be kept in work during treatment (which lasts three to four weeks), which is generally not the case with the histamine blockers. GastroGard is also the only drug that’s approved for treating ulcers in horses.

The catch is that GastroGard is more expensive—$40 to $60 a day, compared to about $15 a day for generic ranitidine. Some compounding pharmacies have produced generic omeprazole products that are cheaper, but researchers at the University of California at Davis have found the generics to be less effective than GastroGard.

The severity of the ulcers, whether you can rest the horse, how much you can change his lifestyle, what you can afford—all these factors affect your choice of treatment. Scoping the horse after treatment will tell you if the ulcers have healed.

Ulcers in Foals

Up to half of foals develop ulcers in the first months of life. The reasons aren’t fully known, but an immature digestive system, illness, or anything that interferes with the ability to nurse may be factors. Ulcers can be more serious in foals than those in adult horses, bleeding and (rarely) perforating the gut wall. Foals also develop ulcers in the duodenum, the entrance to the small intestine; adult horses rarely do.

Be suspicious—and call your vet—if a foal:

• Develops diarrhea, a rough coat, or a pot belly;

• Frequently interrupts his nursing or shows poor appetite;

• Grinds his teeth, drools, lies on his back, or shows signs of colic (indicators of severe pain).






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