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Gastric Ulcers In Horses

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Gastric Ulcers In Horses
Gastric Ulcers in Horses | Innovet Pet

Stomach ulcers are a common problem among humans and horses alike. They're painful, and can make it difficult to eat certain foods. If left untreated, they can even become life-threatening. Fortunately, however, they are also easily preventable. In this article, we'll cover the causes behind stomach ulcers in horses, and provide you with the information you need to get your horse's system back on track.

What Are Gastric Ulcers In Horses?

An ulcer is essentially a sore that refuses to heal. They can be prone to infection and usually require medical treatment to be resolved. Gastric ulcers are ulcers that develop in the stomach. They can cause pain, discomfort, heartburn, and so on. They are very common in horses and are caused by a variety of external factors. A horse's stomach is divided into two sections: the upper and lower sections. The upper section is lined with squamous cells, while the lower section is lined with glandulas that secrete mucous.  

Mucous is an excellent defense against stomach acid and keeps the lower stomach and intestine readily protected against the development of ulcers. The upper section, however, is not so well defended, and therefore tends to be the area where ulcers in horses typically develop. That said, ulcers can definitely appear in the lower stomach as well as the intestine. Horses can develop ulcers at any age and under a variety of conditions.

In fact, ulcers are so common in horses that your horse is more likely to have a stomach ulcer than not. 60% of show and non-performance horses have stomach ulcers, while some 90% of racehorses are affected. Ulcers are typically the result of outside factors, rather than natural illnesses or genetic predispositions. Stress, poor diet, harsh medications, and more can all lead to the development of ulcers in horses. 

What Is Gastritis?

You may have heard your vet refer to stomach ulcers as gastritis. Gastritis is simply a term for inflammation and irritation of your horse's stomach - meaning that gastritis refers to stomach ulcers as well as several other conditions. So a gastritis diagnosis does not necessarily indicate stomach ulcers. Gastritis can usually lead to loss of appetite, poor attitude, underperformance, chewing, and more.

The Different Types Of Ulcers In Horses

ESGUS Ulcers

Equine squamous gastric ulcer syndrome, or ESGUS, is the most common form of ulcers found in ulcers. These are ulcers that occur in the upper portion of a horse's stomach, and they are the result of some form of breakdown in the upper stomach's lining. This damage can occur due to medications, bacteria, parasites, or excessive stomach acid (the result of poor diet or stress). This area of a horse's stomach is especially susceptible to stomach ulcers for two reasons.

The first reason is that it is the first line of defense against whatever is entering your horse's gastrointestinal tract. Any harsh foods, medications, or foreign materials are going to first enter through the upper portion of a horse's stomach. The second reason is that the lining in this area of your horse's stomach is not as resistant to stomach acid as the rest of their stomach. The rest of the stomach is lined with a thick mucous that protects it against stomach acid. The upper portion doesn't have this same protection, making it much easier for ulcers to develop.

EGGUS Ulcers

Equine glandular gastric ulcer syndrome (EGGUS) is the second form of gastric ulcers in horses. These ulcers occur in the lower portion of a horse's stomach and are much rarer than ESGUS ulcers. However, as research advances, it's being discovered that - while still less common - they are more common than previously thought. The mucous lining in this area of the stomach is nearly impervious to stomach acid, which is a common cause of stomach ulcer development.

However, when this mucous lining deteriorates or is damaged in any way, the lower portion of the stomach instantly becomes more susceptible to ulceration. While the exact causes behind mucous lining deterioration are still being defined, it is widely believed that harsh medications like NSAIDs and other pain relievers could be the culprit. These medications inhibit the synthesis of prostaglandins, which are the key ingredients in mucosal protection. Bacteria is another potential cause of this deterioration as well.

What Causes Ulcers In Horses?

Ulcers in horses are almost always caused by outside influence. Wild horses are much, much less susceptible to stomach ulcers. One of the leading causes of stomach ulcers is inconsistent feeding. Horses are designed to casually graze all day long - not to eat two meals at different points during the day. Because horses are designed to eat food in small amounts all day long, their stomach produces stomach acid all day long. And when there's no food for a horse to eat, that stomach acid sits in their stomach, causing damage in the upper portion and making its way through the rest of the gastrointestinal tract.

When a horse grazes all day, this stomach acid is put into action and has little to no effect on a horse's stomach lining. This is due to the saliva that a horse produces when they're chewing. This saliva neutralizes stomach acid, allowing the two to work in tandem to digest food. For this reason, feed that doesn't induce saliva production during chewing can also cause horses to develop stomach ulcers.

Not only can poor feed lead to ulceration, but so can overeating. Since horses are designed to casually graze throughout the day, their stomachs are naturally small compared to their large stature. So trying to give them all of the food they are supposed to eat in a day at two designated mealtimes can cause crowding in their stomach.

Outside Factors

Other outside factors that can lead to stomach ulcers in horses include medication, parasites, stress, and overexercising. In the wild, a horse would very rarely be introduced to any of these factors, which is why many experts call equine ulcers a "man-made disease". It's usually the overwork, intense athleticism, and poor feeding routines that cause horses to develop ulcers, and it's why race horses are the most susceptible to developing stomach ulcers.

Stress and exercise can each cause inflammation throughout a horse's body. Inflammation is a natural immune system response designed to target and attack foreign bodies throughout your horse's system. The issue is that when it is induced by something other than a foreign body - like stress and exercise - the immune system ends up attacking the rest of your horse's body. This response triggers the production of stomach acid, which - as we now know - is the primary cause of ulceration in horses.

Your horse can experience stress as a result of confinement, being ridden poorly, being transported, competing, being overworked or overexercised, and so on. Exercise and work are not bad things in and of themselves; in fact, they are important parts of a horse's life. However, when thrust upon a horse in excess, they can have serious consequences.

Medications can also cause equine ulceration, particularly NSAIDs. NSAIDs are anti-inflammatory medications typically used to treat pain and discomfort. While these medications have been in use for a long time for humans and animals alike, they are currently under scrutiny for causing multiple serious health conditions - including gastric ulcers. They decrease the amount of blood flow that reaches your horse's mucous lining in the lower portion of their stomach, which can cause it to deteriorate and become susceptible to ulceration.

Which Horses Are Most At Risk For Developing Ulcers?

As mentioned, the more overworked a horse is, the higher their chances of developing stomach ulcers. This includes racehorses, show horses, and workhorses. All of these lifestyles create an unnatural amount of stress within a horse's routine, leading to an increase in stomach acid levels, which over time can cause ulcers. Ulcers are not specific to any age in horses, and even foals are found to have them fairly frequently.

While many of the connections between stomach ulcers and their causes are not yet known, there are a variety of predictors that have been to be significant. For instance, keeping stallions in near proximity to female horses can cause them to develop stomach ulcers. This also includes keeping colts near their mothers after they've been weaned.

Not only are ulcers found in horses from all different lifestyles, but they also develop in horses extremely quickly. In fact, it only takes around five days of high stress levels for a horse to start developing stomach ulcers. The truth is that nearly all horses are at high risk for developing stomach ulcers, and there are several outside factors that can increase those chances even more.

Symptoms Of Gastric Ulcers In Horses

Unfortunately, the symptoms of stomach ulcers in horses are usually pretty minimal. This is because horses are great at keeping pain and discomfort to themselves. Symptoms of ulcers in horses can even be as subtle as a change in the quality of their coat, or reduced appetite. Therefore, it is important to keep a close eye on your horse, keep a mental or even a physical note of their normal behavior, and don't hesitate to seek a vet's attention if you believe your horse may have gastric ulcers.

The most common symptoms of ulcers in horses include:

  • Changes in behavior
  • Reduced performance
  • Lack of appetite
  • Reluctance to work/exercise
  • Poor body condition
  • Poor coat quality
  • Weight loss
  • Colic
  • Diarrhea
  • Lethargy

In more severe cases, horses may experience abdominal pains, causing them to grind their teeth and lay in strange positions to relieve the pain. In young horses especially, they are sometimes found laying on their back in an attempt to reduce the pain caused by stomach ulcers. Horses might also salivate excessively, which is the body's way of trying to neutralize high levels of stomach acid.

It's important to keep in mind, though, that even though there are symptoms of ulcers in horses, the majority of horses will appear to be completely healthy for the most part. This is why it's important that you keep a very close eye on your horse, and - especially when dealing with athletic horses - erring on the side of caution is always a plus.

Diagnosis Of Ulcers In Horses

Gastric Ulcers In Horses | Innovet Pet

If you suspect that your horse has stomach ulcers, odds are pretty good that your suspicions are correct. For this reason, it's important that you seek urgent medical care as soon as possible. Aside from being painful, uncomfortable, and reducing a horse's ability to perform and live comfortably, ulcers can cause more severe issues in horses over time.

When you first take your horse in to begin the diagnosis of ulcers, they will start off by putting together a history of the problem and gathering information about your horse's past medical treatments. So be prepared to answer questions, and bring any pertinent paperwork with you. After speaking with you, the vet will most likely conduct standard bloodwork, urinalysis, and complete a biochemistry profile of your horse. All of these tests are just to build up a better picture of your horse's health profile.

When it comes to actually diagnosing a suspected case of ulceration, the most important test is a gastroscopy. This involves placing an endoscope in your horse's stomach and searching for signs of ulcers. To complete a gastroscopy, your horse will need to avoid eating 12-24 hours beforehand and not drink for two to three hours before the test is conducted. This test will inform your vet of the size, severity, and number of ulcers present in your horse's stomach - if any.

Treatment For Gastric Ulcers In Horses

The reason that ulcers require treatment is that they are in an area that prevents them from healing - your horse's stomach. In this location, they are constantly being subjected to stomach acid, which is what initially causes them to develop in the first place. Therefore, treating gastric ulcers in horses generally involves reducing the levels of stomach acid in your horse's stomach and maintaining a healthy pH balance.

The easiest way to begin reducing the severity of your horse's stomach ulcers is by allowing them free access to food. This could mean giving them a pasture with plenty of grass to graze on, a bin that's fully stocked with hay, or something along those lines. You can also improve their diet by decreasing the number of high carbohydrate foods they eat.

Medical solutions to gastric ulcers in horses have been shown to include a proton pump inhibitor, which reduces the amount of acid your horse's stomach creates, as well as H2 blockers, which perform a similar function. Other buffering agents and protective substances might be provided as well that strengthen the lining of your horse's stomach against exposure to stomach acid.

Preventing Gastric Ulcers In Horses

Gastric Ulcers In Horses | Innovet Pet

Fortunately, stomach ulcers in horses are relatively easy to prevent - although it usually requires reworking their lifestyle.
The first thing you can do to reduce your horse's chances of developing ulcers is to give their diet a complete overhaul.

Removing food that's high in carbohydrates is a great first step. You should also provide your horse with a way to freely feed themselves, like giving them a grazing pasture or having hay readily available to them. This will help them neutralize the stomach acid that they naturally produce throughout the day. It's also helpful to provide them with supplements that aid in digestion, as these can help food be processed by their system much easier.

Next, where possible, take measures to ensure that their life is as stress-free as possible. Things like being transported, overworked and overexercised all cause a significant amount of physical and emotional distress on your horse, which can cause their body to produce high volumes of stomach acid. Keeping them on a regular - but less intensive - workout routine will help them maintain their health without overstressing their system.

Another important way to reduce a horse's stress levels is to bring as much stability and consistency into their life as possible. Reducing surprises, managing a familiar schedule, and keeping their environment calm and familiar will all keep a horse's stomach acid levels in a normal range.


While they may be common, stomach ulcers in horses are far from healthy. The kinds of lifestyles that most horses are subjected to aren't conducive to a healthy and comfortable life. If your horse has developed stomach ulcers, the best thing you can do is look for the aforementioned causes in their life and take steps to start cutting back on them where possible.


Equine Gastric Ulcers
Gastric Ulcers in Horses
Diagnosing and Treating Gastric Ulcers in Horses
Ulcers in Horses
Peptic ulcer disease In Horse


    Approved by:

    Dr. Ivana Vukasinovic

    Doctor of Veterinary Medicine, University of Belgrade

    Ivana Vukasinovic grew up in Serbia and attended the University of Belgrade where she received a degree in Veterinary medicine in 2012 and later completed a surgical residency working mostly with livestock. Her first year of practice was split between busy small animal practice and emergency clinic, and after two more years of treating many different species of animals, she opened her own veterinary pharmacy where an interest in canine and feline nutrition emerged with an accent on fighting animal obesity. In her free time, she acts as a foster parent for stray animals before their adoption, likes to read SF books and making salted caramel cookies.












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