The Latest on Equine Ulcers

Ulcers can affect a high percentage of horses—up to 100%, depending on your horse’s job, stress, and breed. 

Horse owners want to better understand equine gastric ulcers because they are so common in many horses. Even retired horses and broodmares that have an idyllic life out on pasture can develop ulcers.

This is part 1 of a two-part article that goes along with The Equine Connection Podcast episodes!

Spotlight on the Horse’s Stomach

Even though horses can have issues throughout their gastrointestinal tracts, the focus of this article is the stomach. There are two important sections in the horse’s stomach—the glandular portion that is on the lower portion of the stomach, and the non-glandular, or squamous, part that is in the upper portion of the stomach. 

Stomach ulcers, as a diagnosis in horses, is relatively recent because it wasn’t until the late 1980s that a gastroscope was designed to be long enough to reach into the equine stomach to visualize the anatomy and problems. 

If you look at a diagram or gastroscopic exam video or photo of the horse’s stomach, it’s easy to see that the top part of the stomach (squamous section) is lighter in color. It has stratified epithelial cells and does not have protection from the acid that is secreted in the glandular (lower) part of the stomach.

The glandular portion of the stomach has a thick mucosal layer that is protected from acid. This portion of the stomach secretes hydrochloric acid, as well as mucous and bicarbonate (which helps neutralize the acid). There are also some hormones secreted in the bottom portion of the stomach that control actions, such as gastric emptying and stomach motility.

There is a distinct area that divides the two stomach sections called the margo plicatus. 

It is interesting that newer research has shown differences in the types of ulcers that form in the squamous (upper) and glandular (lower) portions of the stomach. What was previously referred to as Equine Gastric Ulcer Syndrome, has been separated into Equine Squamous Gastric Disease (ESGD) and Equine Glandular Gastric Disease (EGGD). 

Differences in Types of Ulcers in the Horses Stomach

Ulcers in the squamous (upper) portion of the stomach are usually associated with acid or volatile fatty acids, a byproduct of sugar digestion in the stomach.

Other contributing factors to squamous ulcers include not enough forage in the diet, lack of access to water, an excess of high-starch feeds, intense exercise, and stresses, such as transportation or changing herd dynamics.

Acid from the glandular part of the stomach can “splash up” on the top part of the stomach that doesn’t have protection against the acid. This can create ulcers.

If owners give their horses high-sugar feeds, volatile fatty acids are created. These can exacerbate the impact of acid on the squamous (upper) portion of the stomach.

In the glandular (lower) part of the stomach, there are protective mechanisms in place to guard against acid damage. Research is showing that ulcers in this portion of the stomach aren’t like the ulcers found in the squamous (upper) part of the stomach. 

Ulcers found in the squamous (top) portion of the stomach tend to be “raw” and in severe cases can bleed. Those found in the glandular (lower) part of the stomach tend to be more raised and inflamed. 

Researchers are still identifying why horse’s develop glandular ulcers. Stress and use of non-steroidal anti-inflammatory have been linked to glandular ulcer development. 

Could My Horse Have Ulcers?

There is a lot of data about equine ulcers. For example, researchers have found that 37-52% of Thoroughbreds not in work can have squamous ulcers, and up to 100% of Thoroughbreds in work can have squamous ulcers. 

If you are thinking that your laid-back pony or Quarter Horse doesn’t have any similarities to a racing Thoroughbred, think again! Research has shown that up to 79% of western pleasure horses have ulcers.

Owners of donkeys and mules can’t rule out ulcers in their equids, either! A study showed that 51% of Italian donkeys had ulcers!

Before you think this is a man-made issue, a postmortem study of feral horses in the United Kingdom that had died showed that 61% of them had squamous ulcers. 

Research on glandular ulcers showed that 25-65% of Thoroughbreds in work had these types of ulcers. A study of Canadian show jumpers showed that 72% had glandular ulcers. Another study looked at Quarter Horses, and found that 59% had glandular ulcers.

So, just about any equid can have ulcers depending on the horse, donkey, or mule and its risk factors. 

Risk Factors for Development of Ulcers in Horses

Because of the risk of ulcers in many types of horses, every owner should have ulcers on their radar. Owners should keep in mind that the risk factors for squamous and gastric ulcers are somewhat different.

Squamous ulcers often are a result of management factors. We cover feeding management in-depth in our next podcast and article! Glandular disease seems much more linked to stress.

Some of the clinical signs that might make you think your horse has ulcers could be weight loss, poor body condition score, diarrhea, reduced appetite, behavioral changes, teeth grinding, and “girthiness.” However, even though girthiness has been related by owners of many horses that end up having ulcers, research hasn’t proven a solid relationship.

A retrospective study at the University of California, Davis, showed a high incidence of gastric ulcers in horses reported to have girthiness. But almost as many horses in the study had orthopedic issues, and again, almost as many had a variety of other issues. 92% of the gastroscoped horses in the study were diagnosed with gastric ulcers and as we are learning, many horses have ulcers. Studies have not been conducted to definitively correlate girthiness to ulcers.

Some recent research has looked at possible inciting factors for squamous and glandular ulcer disease. One interesting fact from the research is that as horses are worked more than five days per week, the likelihood that they would have glandular disease increased significantly. That suggests that rest days are really important in mitigating the risk of glandular ulcers. However, the intensity of the work didn’t seem to correlate to either squamous or glandular issues.

Most horse owners know that use of NSAIDs (non-steroidal anti-inflammatory drugs, such as bute or banamine) can increase a horse’s risk of ulcers. More is being learned about drugs that cause ulcers, and even the drugs that treat them. 

How Do I Prevent My Horse from Developing Ulcers?

First, if your horse is diagnosed with an ulcer, don’t beat yourself up! Some horses get ulcers even if you manage them perfectly. One of the biggest things horse owners can do to avoid ulcers in their horses, donkeys, and mules is forage availability. How many hours a day do your animals have access to forage?

Keep horse feed meals as small as possible. We know that some horses need more than hay, but today, we have lower NSC (non-structural carbohydrate) feeds and feeds that are higher in fat that do a great job in providing calories in a way that is more friendly for gastrointestinal health. 

Mitigating stress is a tough discussion because many horses stress themselves. However, we can manage them to help reduce stress. Some people say just turn a horse out on pasture 24/7 and they won’t be stressed. Well, what if your horse hates bugs? So, he’s not eating grass because he is pacing the fence wanting to come back inside.

In part 2 of the podcast and article, we’ll talk more about some of the research that has looked at managing horses to avoid stress and ulcers, as well as discuss treatments.

Final Words

Ulcers are complicated, and we’re all doing our best at trying to manage our horses, donkeys, and mules to avoid issues such as ulcers. 

New research on this topic is incredibly exciting. It’s an evolving area of equine management. 

Always feel free to contact our team if you have questions about your horse, donkey, or mule! 


Check out the Tribute® products developed to help horse owners better manage their horse’s diets for specific needs.

Constant Comfort® Pellet

  • The Constant Comfort® gut health supplement system offers your horse 24/7 support and is comprised of two products: Constant Comfort® Plus and the Constant Comfort® Block. Constant Comfort® Plus is a top dress that should be fed at regular feedings and before times of stress. It provides your horse with Aloe Vera, Glutamine and Lecithin to help soothe their stomach and support their stomach lining, as well as Seaweed Derived Calcium to maintain proper stomach pH. It also contains Equi-Ferm XL®, a pre- and probiotic that supports hindgut health. We recommend using the Constant Comfort® Plus in conjunction with the Constant Comfort® Block.

Constant Comfort® Block

  • Your horse’s stomach secretes acid continuously, so they need support all day and night – not just at feeding times. The Constant Comfort® Block is designed to help soothe and support your horse’s stomach 24/7 when offered free-choice. It contains Seaweed Derived Calcium to maintain proper stomach pH, as well as Equi-Ferm XL®, a pre- and probiotic that supports hindgut pH, overall digestive health and total diet digestibility. We recommend using the Constant Comfort® Block in conjunction with Constant Comfort® Plus.

Kalm ‘N EZ® Pellet

  • Kalm ‘N EZ® Pellet is higher in fat (8%), high in fiber (20%), very low in NSC (13.5%) and does not have any added iron. This feed is suitable for moderate to harder-keeping horses with sugar and starch sensitivities, including Insulin Resistance, PSSM Type 1 and other metabolic disorders. The low sugar and starch (NSC) levels also make it an excellent choice for hyperactive horses and horses with digestive tract sensitivities. Its high fiber level also makes Kalm ‘N EZ® Pellet a great option when hay quality is poor or hay replacement is necessary. This feed is formulated with pre- and probiotics to support your horse’s digestive health.

Senior Sport®

  • Senior Sport® was designed with the hard-keeping and hard-working horse in mind. This textured feed is high in fat (10%), high in fiber (18%), and low in NSC (16.5%), making it suitable for horses with sugar and starch sensitivities that also have higher calorie needs. Its high fiber level makes it a great option when hay quality is poor or hay replacement is necessary. Senior Sport® is also formulated with pre- and probiotics to support your horse’s digestive health and does not contain any added iron.
Article By: Kimberly S. Brown
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