Feeding the Ulcer-Prone Horse

How to craft a diet for the horse with painful lesions in his stomach

Which horses would you traditionally consider “ulcer-prone”? Racehorses in training? Western pleasure horses showing competitively on the American Quarter Horse Association circuit? Pony Clubbers’ games ponies? Injured horses on stall rest? Truth is, you could be right with any one of these.

Equine gastric ulcer syndrome (EGUS) can plague any age, breed, or sex, and the risk factors are many—certain types of training and exercise, nutrition, feeding practices, and stabling, to name a few. Let’s take a look at one very important aspect of preventing and managing ulcers: diet.

The Facts and Stats

The Equine Gastric Ulcer Council defines EGUS as a disease complex associated with ulceration of the esophageal, gastric, or duodenal mucosa. Clinical signs can include a reduced or poor appetite, weight loss, a dull skin and hair coat, attitude or behavior changes, impaired performance, reluctance to work, and colic. Researchers have yet to determine a very reliable detection method for ulcers via blood and fecal markers. Therefore, veterinarian-performed gastroscopy (viewing the horse’s stomach using a flexible lighted instrument passed through his nostril) is the only accurate diagnostic test.

The council estimates that 30-50% of all foals and more than 50% of symptomatic ones have ulcers, and about 90% of symptomatic mature horses (older than 2) have ulcers. In the absence of any outward signs, about half of all mature horses have ulcers.

In 1986, a research study supported by the Royal Hong Kong Jockey Club brought awareness to the prevalence of equine gastric ulcers, specifically in racehorses. The researchers found that 66% of racehorses suffered from gastric ulcers, with that number rising to 88% if horses were actively training at the time. Statistics are likely similar among horses of other breeds and disciplines, and recent survey data appear to confirm this marked prevalence of ulcers in performance horses.

EGUS Prevalence Across Disciplines

Performance Type Prevalence Reference
Endurance (off-season) 48% Tamzali et. al., 2010
Endurance (competition season) 93% Tamzali et. al., 2010
Western Performance 40% Bertone, 2000
English Performance 60% McClure et al., 1999
Pleasure/Leisure 53% Luthersson et al., 2009
Standardbreds and Thoroughbreds 58-88% Orsini et al., 2009; Beli et al., 2011
Swedish Trotters 70% Jonsson et al., 2006

Nutritional Risk Factors

The way we feed our horses, from meal size to forage type, can increase or lower their risk of developing gastric ulcers.


Consider the horse’s natural food consumption pattern: grazing throughout the day, consuming small forage meals. Mastication, or chewing, stimulates glands in the mouth to produce saliva, which begins food breakdown and lubricates it to be swallowed. Food’s arrival in the stomach causes release of enzymes and acids, including hydrochloric acid that helps break food down into individual nutrients, such as vitamins and minerals. But it is actually secreted continuously, even in the absence of food.

It only makes sense that a prolonged amount of time between meals, as is common for domesticated horses, contributes to ulcer formation and exacerbation. The chemical makeup of the food itself, combined with saliva and with buffers such as bicarbonate released by the stomach, helps protect the stomach’s mucosal lining from potential ulcer perpetrators such as hydrochloric acid.

Nanna Luthersson, DVM, partner at Hestedoktoren, a Danish veterinary clinic, and coworkers confirmed that a time span greater than six hours between forage meals increases the likelihood of EGUS.


Much of the starch in a horse’s diet comes from cereal grains such as corn and oats. Starch is an excellent source of digestible energy, or calories, for horses, but, says Luthersson, “Some of our work has confirmed that diets exceeding 2 grams per kilogram of body weight of starch per day (are) associated with an approximately twofold increase in the likelihood of EGUS severity in a subpopulation of Danish horses.”

Her team also found that horses consuming more than 1 gram of starch per kilogram of body weight per meal were 2 1/2 times more likely to develop ulcers. In this study, workload did not increase the risk of ulcers. Researchers on other studies have confirmed that ulcers form in nonworking horses simply from being stabled and consuming concentrate meals.

“(Cereal grains) tend to be low in calcium and possibly other potential buffering agents, which may also contribute to the increased risk of ulceration,” Luthersson says.

Forage type

The stomach also houses a diverse mixture of bacterial microflora that ferment nonstructural carbohydrates (NSC) to create volatile fatty acids (VFAs). In 2003 Jenifer Nadeau, PhD, and colleagues at the University of Tennessee found that starch- and sugar-rich diets increase VFA production in the horse’s stomach and reduce mucosal lining integrity, leaving it susceptible to gastric acids. Forage consumption typically produces more saliva than concentrate or grain consumption does simply because forages require more chewing and, therefore, stimulation of the salivary glands. Forage itself can also help buffer acids due to its nutritional makeup. This is especially true with legumes such as alfalfa that have a higher protein and calcium content.

In another study performed at the University of Tennessee, the researchers found that horses consuming an alfalfa hay and grain diet had fewer ulcers and lower gastric acidity than those eating bromegrass hay (a warm-season grass forage) without grain. And researchers in Denmark determined that straw (a very low-quality forage) consumption, when used as either bedding or the sole forage source, increased gastric ulcer formation.

“Straw may provide low levels of buffering support, due to its low protein and calcium content, plus its physical nature may result in mucosal irritation,” says Luthersson.

Reducing the Risks

“Early studies reported that removing an afflicted horse from the training environment and turning it out to pasture would result in (ulcer) healing,” says Alfred Merritt, DVM, MS, ACVIM, professor emeritus at the University of Florida College of Veterinary Medicine, in Gainesville. More recent reports indicate ulcer formation might not be dependent on turnout amount. Even so, nutritional strategies to minimize ulcer formation are still fairly simple—few advances have been made in this area. Practical feeding recommendations include:

1. Provide a quality forage-based diet. Luthersson says consuming a large amount of saliva-stimulating forage might help reduce ulcer incidence. The latter University of Tennessee study results suggest that feeding alfalfa hay, in particular, might reduce the number and severity of ulcers.

“Alfalfa may actually be protective by virtue of its higher calcium and protein content that act as buffers of the gastric acid,” says Merritt.

Feed long-stemmed hay at a minimum of 1-1.5% of body weight throughout the day, and make sure straw does not make up more than 25% of the total forage in the diet.

When feeding concentrate, also providing alfalfa hay might help buffer the effects of gastric acid and reduce the number of ulcers that form. For horses on a high-grain diet, such as those working at intense levels (i.e., racehorses), quality alfalfa hay can serve the dual purpose of also providing a digestible source of nutrients and potentially reduce the total amount of grain fed per day.

2. Regulate starch intake not to exceed 2 grams of starch per kilogram of body weight per day or 1 gram of starch per kilogram of body weight per meal. For horses that require large amounts of grain, such as high-performance athletes, feeding at least three meals per day at six-hour intervals or less will reduce the volume of starch per meal.

For horses on stall rest due to injury, transition them gradually to a forage-based diet. You can use a low-starch and -sugar ration balancer to augment the protein, vitamins, and minerals provided by the forage without feeding an excessive amount of calories.

3. Extend time spent foraging either by providing pasture turnout or using techniques (e.g., haynets or feeders with small holes, hay piles spread around the space) to slow down a horse’s hay consumption while stabled or in a drylot.

Feed idle or overweight horses a lower-calorie forage that they can consume continuously throughout the day.

4. Provide vegetable oil as a calorie source. In a study of ponies (Cargile et al., 2004), supplementing corn oil decreased gastric acid production and potentially ulcer development.

You can reduce the concentration ration for horses consuming large amounts by replacing some of the calories with fat. When doing so, balance the total diet to make sure vitamin and mineral needs are being met. Replacing sugar and starch with fat can also help reduce hyperactivity, important for horses recovering from injury and stalled for long periods.

5. Ensure water is available at all times when stabled and pastured, and monitor water intake. During transport, provide water at intervals not exceeding four to six hours.

Take-Home Message

Today’s feeding practices can put all horses at risk for developing EGUS, although performance horses are the most likely candidates. Managing horses and their diets carefully can help greatly reduce the risk of ulcer recurrence or severity.