Equine ulcers are a significant concern for many horse owners. Ulcers can affect all types of horses and have a variety of causes and clinical signs. Performance horses are especially prone to developing ulcers due to their lifestyle and exercise programs.

As a horse owner, it’s important to understand the types of equine ulcers, symptoms, causes, and treatments, as well as how best to prevent reoccurrence.

Peter Heidmann, DVM, a board-certified internal medicine specialist, and Bryan Dubynsky, DVM, a sport horse medicine specialist, of Palm Beach Equine Clinic in Wellington, Fla., are both experienced in identifying, treating, and helping owners prevent equine ulcers.

According to Heidmann and Dubynsky, equine ulcers can be grouped into two categories: gastric ulcers and hindgut ulcers. The horse can develop one or the other, or both in combination. Gastric ulcers, which are the most common, develop in the stomach, while hindgut ulcers are found in the colon.

Clinical Signs

Signs of gastric and hindgut ulcers can range in type and severity. A common indicator of ulcers in many sport horses is poor performance in the arena. Horses may also present symptoms of abdominal discomfort, such as girthiness or even colic. Other more subtle behaviors can also be warning signs.

“A symptom that people do not always realize is that sometimes horses will act like they are sore over their withers,” says Heidmann. “Horses with gastric ulcers will be reluctant to drop down if you pinch their withers because it shifts where the stomach is in their body, and it feels uncomfortable.

“Another classic sign that sometimes goes under the radar is eating slowly or suddenly becoming a picky eater,” he continues. “The horse may look hungry, walk up to food, take a bite or two, and then walk away from it with a sour look on his face. If I see that while I’m walking through a barn, it’s usually a trigger for me to consider looking into ulcers.”

Causes of Ulcers in Horses

One of the most common causes of gastric ulcers is stress. Some horses internalize their stress more than others, which can make them more prone to developing ulcers.

“Horses who are more worried or are in an environment that doesn’t suit them are at a higher risk for developing ulcers,” says Heidmann. “It’s not as much about breed as it is job, temperament, and environment. Something as simple as stall placement could affect the horse. The lead mare in the big barn might want to be in the middle of everything, whereas another horse may want a quieter stall. Apparently even small things like that are at play.”

Since performance horses are often traveling and put under stress for their job, the risk for gastric ulcers is higher.

“Gastric ulcers can be a significant health concern in sport horses,” says Dubynsky. “Studies show that 50 to 90 percent of all competing horses have gastric ulcers. Intense exercise, dietary changes, stress, and confinement can all contribute to the development of ulcers in these horses.”

In addition to the horse’s stress level, job, and environment, medication can also lead to gastric and hindgut ulcers. For example, chronic administration of non-steroidal anti-inflammatory drugs (NSAIDs) can result in both types of equine ulcers.

Diagnosing Ulcers in a Horse

Once symptoms have been acknowledged, proper diagnosis is the next step. For gastric ulcers, a gastroscopic examination of the stomach in a fasting horse is critical to the process.

“A gastroscopic exam not only tells you if the horse has ulcers or not, but the procedure helps you determine the severity and location,” explains Heidmann. “This information helps dictate the best treatment plan and what medication we prescribe, for how long, and a plan for prevention in the future.”

A gastroscopic exam is often repeated at the end of a treatment cycle to determine whether it was successful and if the horse needs to remain on medication. The procedure is very safe and can be performed easily.

Hindgut ulcers are more challenging to diagnose. The ideal strategy is a combination of an ultrasound and a fecal blood test.

“Ultrasound allows us to look at the colon, see wall thickness, and then by putting a lot of pieces together, we can infer if there is inflammation or not,” says Heidmann. “You can only see about 60 percent of the colon on an ultrasound because part of it points to the center of the abdomen that you can’t see. This means you can miss things, even with the best technology.”

Since an ultrasound doesn’t always provide a definitive diagnosis, the fecal blood test can be used as well. This test can have a high instance of false positives, so it is best to use it in combination with the ultrasound to determine if the horse has hindgut ulcers.

Treatment Options

Once equine ulcers have been diagnosed, a treatment plan is developed based on the information that has been gathered. Depending on the type and area of the ulcers, different medications may be given.

Omeprazole paste has been shown to be effective for treating gastric ulcers. However, misoprostol can also be added to the treatment regimen, especially for hindgut ulcers.

“There is some research comparing the efficacy of omeprazole products versus misoprostol for treating gastric ulcers in the lower stomach,” says Heidmann. “Depending on where the ulcers are in the stomach, we may do a combination of both medications. If the ulcers are up high in the stomach, then the omeprazole product does very well. If there are ulcers in the glandular and pyloric region of the lower stomach, then we often recommend a combination of both omeprazole and misoprostol.”

Prevention of Ulcers

Once ulcers have been treated, understanding how best to prevent them from reoccurring is critical. This is especially important for performance horses who are more susceptible to developing ulcers as a result of their lifestyle.

“It is crucial for horse owners and trainers to be vigilant in monitoring their animals’ well-being,” says Dubynsky. “If ulcers are suspected—the first symptom usually being behavior change—it’s important to seek veterinary advice. Proper management practices, such as providing a consistent feeding schedule, reducing stress, and using medications or supplements to support gastric health, can help prevent and manage ulcers in sport horses, ensuring their overall [health] and performance.”

In addition to reducing stress, one of the most important ways to help prevent ulcers is allowing horses to have free-choice access to pasture grazing or hay. This increases the buffering effect of constant saliva production, meaning the high pH of equine saliva helps neutralize the low pH of stomach acid. Additionally, a soft hay such as orchard grass may help to relieve discomfort with hindgut ulcers.

“Horses evolved to be grazing 16 to 19 hours of the day,” says Heidmann. “When we domesticate horses, put them in a barn, and feed them a few flakes three times a day, the risk for ulcers goes way up. When horses can continuously graze, it also allows saliva—produced by grazing—to be a buffering agent. Saliva is very protective of the stomach.”

Some feed adjustments may help prevent ulcers. Try to avoid high-sugar feeds that make the stomach more acidic as a result of the feedstuff being digested.

Adding alfalfa hay or pellets to a horse’s feeding program may reduce the incidence of gastric ulcers as well. Alfalfa has less sugar than grass, is energy-dense, and contains high levels of calcium and magnesium—think “Tums for horses.”

If you suspect ulcers, it’s important to discuss diagnostic and treatment options with your veterinarian immediately. The best approach for horse owners is to be aware of the clinical signs of equine ulcers in order to prevent this debilitating disease.

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How Equine Microbiome Work

Horses evolved to extract a remarkable amount of nutrients out of relatively poor-quality feed. In the wild, they walk around all day, eating for the majority of a day’s 24 hours. Here’s how the system works.

◆ First, the food passes through the mouth and gets mixed (chewed) with a lot of water and enzymes in the saliva; enzymes help speed up the chemical reactions that occur when food is digested.

◆ Next, the food goes into a tub (aka the stomach): a fairly small tub, actually, given the size of the horse. In the stomach, the food gets mixed with more enzymes and acid, and proteins in the feed start to break down. From the stomach, the feed gets released into a long tube.

◆ The small intestine of the horse is long. Really long. Seventy feet long. But the food moves through quickly, biologically speaking. It travels about a foot per minute and can get back to the hindgut in as little as 45 minutes, depending on how much and what kind of food. In the small intestine, carbohydrates, fat, and protein get digested (by more enzymes and absorbed.

◆ The horse’s hindgut is where the things that make the horse’s digestive system so unique happen. The hindgut (cecum, large colon, small colon and rectum) isn’t nearly as long as the small intestine, but it can handle a lot more feed.

In the hindgut, the horse has countless numbers of microbes (bacteria, protists, fungi, even viruses) that help break down the stems and woody parts of the horse’s forage. The microbes do the important work of fermentation, which in addition to producing fatty acids, amino acids, and B vitamins for the horse, also make the horse gassy.

It’s in the hindgut that a great deal of water is absorbed, as well.

The Equine Microbiome

The microbiome breaks down food to release energy—but that’s not all. It also protects the horse against “bad” bacteria; is involved in the horse’s immune system, helping keep the animal from getting sick; and even produces many of the vitamins that the horse needs.
It’s an area of current research because understanding the equine microbiome is critically important for understanding the horse’s health, as well as for understanding what we can and cannot do for the horse.

Before you can effectively try to modify the equine microbiome, it’s important to know what’s in it. Using genetic sequencing of bacteria (instead of trying to grow them), scientists are finding out that the horse’s GI tract has many more kinds of bacteria in it that was initially thought, especially those that live without oxygen (anaerobic bacteria).

As it turns out, the microbiome of most horses is actually quite similar. The microbiome of a Quarter Horse in Texas is about the same as the microbiome of a warmblood in Connecticut. For the vast majority of horses in different seasons, on different diets, and in different locations, there seems to be something of a normal range for the bacteria in the horse’s GI tract.

What Alters the Microbiome?

Certain things can rather predictably alter the equine microbiome. For example:
Nutrition: When horses eat large amounts of grain in their diet, their microbiome changes. Veterinarians have long known that large amounts of grain are associated with all sorts of diseases, including laminitis and colic.

One reason is that large amounts of grain change the bacterial population. As long as a horse gets enough forage (fiber from hay or pasture), giving him some grain doesn’t seem to affect the microbiome. It’s at high concentrate levels—such as are fed to racehorses—that the microbiome changes.

While changes in the horse’s microbiome probably also changes some of the physiologic processes of the horse, it’s too early to say if this change directly causes disease. In many other species, it’s been shown that the microbiome is slightly sensitive to things like diet, season, and acute changes in diet; however, these changes aren’t necessarily associated with disease. This is food for thought and future research.

Antibiotic use: Antibiotics kill bacteria. The gut is full of bacteria. Antibiotics can affect the microbiome, and different antibiotics affect different bugs. That’s easy to understand. Perhaps less easy to understand is why antibiotic-induced diarrhea isn’t more of a routine problem in horses.

Disease: When there’s intestinal disease, e.g., colitis, there are also big changes in the microbiome. It’s been shown in at least one study that the microbiome of horses that colic is different from the microbiome of horses that don’t colic, but it’s too early to say that a change in the microbiome will always cause a horse to colic. It’s another area for future research.

To make things even more complicated, all disease-caused changes to the equine microbiome are not created equal. For example, horses with diarrhea caused by Salmonella bacteria appear to have a different microbiome from horses with diarrhea caused by antibiotics.
If that’s the case, it may be possible to develop a microbiome index to see if it’s possible to tell what might have caused the changes. Such efforts are underway.

The Question of Probiotics

People with GI disease, such as Crohn’s Disease, inflammatory bowel disease, and the like, have different microbiomes than healthy people. However, it’s not yet known if that’s the case in horses.

Although “supporting,” “improving,” or “protecting” microbiome is a goal of equine digestive products everywhere, giving such products—for example, pre- or probiotics—doesn’t magically make a horse’s GI tract safe, secure, and efficient.

While the relatively few bacteria that are in equine probiotic products may provide some benefit, they do not “normalize” the equine GI tract. There are a few other things that are known.

◆ The horse’s stomach is, among other things, a vat of acid. Acid is one of the worst things you can run into if you’re a bacterium, and there’s a lot of question about how much, if any, bacteria can survive the stomach if you squirt some in a horse’s mouth.

◆ Probiotics are not drugs, and they aren’t regulated as drugs. This is to say that you really have very little idea what you’re giving when you’re giving a horse a probiotic.

◆ There’s also the problem of content. Various products may not contain the bacteria that are said to be in them, the bacteria in the product may not be alive, and the cell count (the colony forming units, or CFU) may not be as advertised.

◆ There’s the question of dose. In humans, products may have as many as 900 billion CFUs, and humans are about 10 percent of the size of most horses. While equine products vary, the doses are usually much, much smaller. Even if a product were to be effective, a dose of 2 billion CFU (or even 25 billion) isn’t like to go very far in a horse.

When it comes to the equine microbiome, scientists don’t yet know enough about what’s normal to go about making any strong recommendations or having any firm conclusions about what to do when things are abnormal. Happily, horses seem to do pretty well without any help, even though there’s certainly a lot more to learn.

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