Squamous vs Glandular Ulcers in Horses: What’s the Difference?

Gastric Ulcers
Squamous
Glandular
Prevalence
Risk
Diagnosis
Signs
Treatment
Prevention

What’s the difference between squamous ulcers and glandular ulcers in horses? Different types of stomach ulcers in horses are commonly described as the general diagnosis of Equine Gastric Ulcer Syndrome (EGUS).

However, new research suggests it is better to refer to gastric ulcers as two different syndromes depending on the location of ulceration.

Equine Squamous Gastric Ulcer Syndrome (ESGUS) refers to ulcers affecting the upper squamous region of the stomach.

Equine Glandular Gastric Ulcer Syndrome (EGGUS) refers to ulcers affecting the lower glandular region of the stomach. ^[1]^[5]

Equine gastric ulcers are all too common, affecting up to 93% of horses. Ulcers are painful lesions that form in the lining of the gastrointestinal tract.

Ulcers can result in impaired nutrient absorption, discomfort, digestive complications and poor performance in your horse.

Traditionally, veterinarians and horse owners treated and managed all gastric ulcers the same way. However, the etiology physiology of ulcers differs depending on the region of the stomach in which they appear.

Research shows that there are different risk factors and causes for squamous ulcers compared to glandular ulcers. There are also different treatment and management strategies recommended for EGGUS vs. ESGUS.

Understanding the differences between these two ulcer syndromes can help you identify, prevent, and manage gastric ulcers in your horse.

Overview of Gastric Ulcers

Equine gastric ulcers are sores or lesions in the lining of the stomach. EGUS is one of the most commonly diagnosed health conditions in horses.

Horses are usually diagnosed with the umbrella term Equine Gastric Ulcer Syndrome. This diagnosis can include ulcers of the squamous region and ulcers of the glandular area.

Ulcers that appear in the upper squamous region are more common than those that develop in the lower glandular region, largely due to the different natural defence systems these two regions have against ulcers.

Below, we will review further differences in risk factors, causation, diagnosis, treatment, and prevention of squamous versus glandular ulcers. ^[1]

The equine stomach is small but complex. It can be broken into two sections: the squamous and glandular regions. Ulcers develop in these two regions for different reasons.

Equine Squamous Gastric Ulcer Syndrome (ESGUS)

Up to 80% of all equine ulcers are found in the squamous region of the stomach. The causes and risk factors for ESGUS are well understood.

The squamous region covers roughly one-third of the stomach. Food passes through the esophagus and enters the squamous region, before reaching the glandular region. ^[2]

Cells in the lining (epithelium) of the squamous region do not produce mucous or bicarbonate. This makes this region distinct from the glandular stomach, which is capable of producing mucous or bicarbonate.

Mucous secreted from epithelial cells forms a mucosal membrane that protects stomach tissue from gastric acids. The gastric mucosa also secretes bicarbonate, which helps to neutralize acids in the stomach.

The glandular region of the stomach is better protected against ulcers because of these defence mechanisms. However, the stomach lining of the squamous region which lacks the ability to produce mucous or bicarbonate is not as well protected.

This is why ESGUS is significantly more prevalent than EGGUS. ^[3]

It is noteworthy that the squamous region does not itself secrete gastric acids. However, acids secreted in the glandular region often splash into the squamous area, particularly during exercise.

Consumption of feed actually helps to prevent some of the damage caused by gastric acids in the squamous lining. When food, saliva, and water enter the squamous region from the esophagus, they can work to buffer some of these acids.

However, when the stomach is empty, this region is more exposed to harmful acids. Feeding your horse many small meals throughout the day can help to reduce ulcer risk.

The squamous region is more susceptible to ulcers because it does not produce mucous or bicarbonate. Gastric acid can splash into this region and cause ulcers, particularly when the stomach is empty or when exercising.

Equine Glandular Gastric Ulcer Syndrome (EGGUS)

Very little is comparatively known about EGGUS and the pathophysiology of this disease.

The glandular region comprises the bottom two-thirds of the stomach. ^[2] This region is where acid secretion takes place.

The major gastric acid secreted is hydrochloric acid (HCl). Pepsin and gastrin are also secreted in this region. These acids activate digestive enzymes to begin the breakdown of food.

As discussed previously, the glandular region produces bicarbonate and mucous. These compounds buffer gastric juices and line the stomach wall of the glandular region protecting it from acid damage.

Therefore, acid damage is not usually the cause of EGGUS. Rather, it appears that interference with mucous and bicarbonate secretion or mucousa integrity can cause ulcers in this region. ^[3]

The glandular region naturally produces mucous and bicarbonate to protect against ulcers. Less is understood about why EGGUS occurs.

Gastric Ulcer Prevalence in Horses

Equine ulcers are extremely common, but the prevalence is much higher for ESGUS compared to EGGUS.

Prevalence depends on lifestyle, diet, and environmental factors. It varies considerably between squamous and glandular ulcers.

Prevalence of ESGUS

For squamous ulcers, the prevalence appears highest in racing, or performance, horses. Specifically, Thoroughbred racehorses have the highest prevalence.

Untrained Thoroughbred horses have an estimated prevalence of 37%. Thoroughbred horses in training for more than 2 months have reported prevalence between 80-100%. ^[11]^[12]^[13]

Standardbred racehorses have a similar but slightly lower prevalence of ESGUS. Only a 44% prevalence is reported in untrained Standardbred horses but up to 87% of training Standardbred racehorses are affected by squamous ulcers. ^[14]^[15]

Forty-eight percent of non-competing endurance horses are affected by ESGUS. ^[8] This prevalence increases to 93% when competing. ^[16]

Furthermore, up to 58% of both show and pleasure horses are affected by ESGUS. ^[17]^[18]

Prevalence of EGGUS

There is limited research on the prevalence of EGGUS in horses. Up to 65% of Thoroughbred racehorses may be affected by EGGUS. ^[6]

Competing endurance horses are thought to have a prevalence of between 27-33 %. The prevalence of glandular ulcers is approximately 16% when not competing. ^[7]^[8]

Preliminary data suggests that Warmblood horses are most likely to be affected by EGGUS. ^[9] However, only one study has shown this association when compared to other horse breeds.

The prevalence of EGGUS in show horses is unclear. Up to 54% of pleasure horses are reported to be affected by EGGUS. ^[10]

Gastric ulceration is one of the most prevalent health conditions affecting horses. Rates of squamous region ulcers are up to 93% for some groups of the equine population. The prevalence of glandular region ulcers is lower, affecting up to 65% of competing horses.

Risk Factors for ESGUS and EGGUS

Current research on risk factors for equine ulcers tends to focus on EGUS as a whole. As new findings emerge, they show there are clear differences between the risk profiles for ESGUS and EGGUS.

The risk of squamous ulcers is related to increased exposure to damaging acids along the stomach lining. ^[3]^[4]

The development of glandular ulcers involves dysregulated tissue function such that the protective barrier of the stomach is impaired. ^[3]^[4]

Risk Factors for Squamous Ulcers

Common risk factors for ESGUS include: ^[3]^[4]^[5]

High-intensity training
High grain or concentrate intakes
Intermittent feeding regimen
Limited turnout
Changes to the social environment
Lack of routine
Travel and competition

Risk Factors for Glandular Ulcers

Risk factors for EGGUS include factors that weaken or lessen the integrity of the protective functions in the glandular region.

Research shows that the following are correlated with an increased risk of EGGUS: ^[3]^[4]^[5]

Long-term non-steroidal anti-inflammatory drug use (NSAIDs)
Limited turnout
Short, intense exercise
Breed (i.e. Warmblood)
Presence of Pathogenic bacteria
Low hay intake
High unprocessed grain intake
Feeding an incomplete or unbalanced diet

Diet, feeding regimens, and excessive exercise are greater risks for squamous than for glandular ulcers. Stress and NSAID use are more likely to contribute to glandular ulcers.

Diagnosing Gastric Ulcers

To formally diagnose equine ulcers, a veterinarian will perform a gastroscopy.

This procedure uses a small, flexible tube fitted with a camera at the end which is passed through your horse’s mouth into their stomach. Your veterinarian will be able to clearly see the esophagus, stomach, and upper intestine to check for ulcers.

This allows the vet to assess the number and severity of ulcers present. This procedure can also identify which area is affected (i.e. squamous or glandular region).

Your veterinarian can use gastroscopy to determine a grade or score for your horse’s ulcers. Scores range from 0 to 4 and determine the severity and level of ulcerations.

Grading Ulcers

Grade/Score	Squamous Ulcers	Glandular Ulcers
0	Epithelium is intact. No appearance of hyperkeratosis (yellowing of the mucosa).	Epithelium is intact. No evidence of hyperaemia.
1	Mucosa is intact. Areas of hyperkeratosis.	Mucosa is intact. Areas of hyperaemia.
2	Small, single, or multifocal superficial lesions (less than 5)	Small, single, or multifocal superficial lesions (less than 5)
3	Large, single deep, or multifocal superficial lesions (greater than 5)	Large, single deep, or multifocal superficial lesions (greater than 5)
4	Extensive lesions. Areas of apparent deep ulceration.	Extensive lesions. Areas of apparent deep ulceration.

This method is the only definitive way to diagnose gastric ulcers. However, it can be expensive and is not always accessible to all horse owners.

Due to the high prevalence of ulcers, it is common practice to assume that a horse is affected by this condition if they display certain characteristic signs or symptoms.

Additionally, many horse owners incorporate safe, natural preventative strategies for equine ulcers as part of their horse’s daily routine.

Signs & Symptoms of ESGUS & EGGUS

There are many differences between ESGUS and EGGUS. However, the signs and symptoms are relatively similar.

If your horse exhibits any of the following signs and symptoms of equine ulcers, contact your veterinarian: ^[3]^[4]^[5]

Poor appetite or picky eating
Chronic diarrhea
Weight loss and/or poor body condition
Stretching to urinate
Increased aggression
Decreased exercise performance
Poor hair/coat condition
Recurrent colic
Behavioural changes (ie. anxiety)
Sensitivity in the girth area (girthiness)
Cribbing, teeth grinding, and other stereotypic behaviours
Excessive salivation
Excessive recumbency (lying down)

Treatment of ESGUS & EGGUS

After a diagnosis, your veterinarian will develop the best treatment plan for your horse. Strategies to treat ulcers differ between ESGUS and EGGUS.

Traditionally, squamous ulcers and glandular ulcers were diagnosed under the umbrella term of EGUS instead of being diagnosed as two separate conditions. It was typical for ESGUS and EGGUS to be treated in the same way.

However, emerging research demonstrates that there are differences in the efficacy of treatments depending on where ulcers present.

The only FDA-approved drug for ulcers is omeprazole, sold under the tradenames GastroGard or UlcerGard.

Omeprazole is effective for treating ulcers in the squamous region. However, omeprazole appears to be less effective for treating glandular ulcers. ^[6]

Treatments for ESGUS

1. Omeprazole

This drug is a proton pump inhibitor. It irreversibly blocks the production of gastric acid to increase the pH level (reduce acidity) in the stomach.

In the stomach, proton pumps use an enzyme to trade hydrogen ions for potassium ions. Once absorbed, omeprazole binds to this enzyme and prevents the pump from working properly, which decreases hydrogen chloride production. ^[19]

Veterinarians often prescribe omeprazole treatment to horses with ESGUS. Omeprazole is administered orally once a day at a dose of 4 mg/kg body weight (2000 mg omeprazole for a 500 kg horse). ^[20]

Treatment often lasts for four weeks or 28 days. It is usually recommended to continue treatment for another four weeks at 2 mg/kg body weight to wean your horse off of omeprazole.

This can reduce the risk of acid rebound. However, even with this weaning-off protocol, the risk of ulcer rebound after finishing omeprazole treatment remains high.

2. Ranitidine and Cimetidine

These two drugs are histamine H2 receptor blockers that also reduce the production of gastric acid. These options are often cheaper than omeprazole.

However, studies show that ranitidine and cimetidine are less effective at treating ulcers than omeprazole. ^[21]

3. Antacids

Antacids have long been used to treat gastric ulcers. They neutralize gastric acids instead of inhibiting their production. ^[22]

Antacids have been shown to increase the stomach pH levels in horses for short durations (2 – 4 hours maximum). ^[23]

They are less likely to be recommended due to their temporary efficacy and potential adverse effects on digestion. ^[24]

Treatments for EGGUS

1. Misoprostal

Misoprostol is a synthetic prostaglandin, which is a type of immune compound that inhibits acid secretion and stimulates mucous secretion in the glandular stomach.

As a prostaglandin analogue, misoprostol may improve glandular mucous barrier function and integrity.

Research shows that horses treated with misoprostol exhibit increased mucous and bicarbonate production. Additionally, misoprostol has shown anti-inflammatory effects. ^[25]

One clinical trial in horses with glandular ulcers showed that misoprostol treatment was more effective than omeprazole. ^[26]

2. Sucralfate

Sucralfate is a mucosal protectant. It forms a physical barrier to protect the gastric mucousa against degradation by gastric acids. This helps facilitate ulcer healing and decreases pain associated with ulcers. ^[27]

Administration of sucralfate in horses also improves the secretion of mucous and bicarbonate. This can provide further protection for the stomach lining.

Sucralfate is often administered alongside other treatment options such as omeprazole to increase its efficacy. Timing of administration and your horse’s feeding schedule needs to be carefully managed so as to not impair absorption. ^[3]

3. Omeprazole

Treatment for EGGUS may also include omeprazole. However, studies show that omeprazole is only 25% effective at treating ulcers in the glandular region. ^[6]

If you notice signs & symptoms of ulcers in your horse, contact your veterinarian. Your veterinarian will be able to evaluate your horse and develop a treatment plan.

Prevention and Management of Ulcers

There are many changes you can adopt in your horse’s feeding and management to prevent gastric ulcers.

Some strategies work to prevent both ESGUS and EGGUS. However, specific strategies may be better for squamous ulcers while other strategies target glandular ulcers.

Lifestyle Strategies

Incorporating some of the following changes in your horse’s daily routine can naturally reduce ulcer risk.

Avoid intermittent feeding
Provide constant access to water
Increase turnout
Reduce grain consumption
Increase haylage and hay quality
Minimize NSAID use
Provide your horse with a suitable social group

Feeding Strategies

Certain hays are known to reduce ulcer risk, such as protein-rich alfalfa hay. Feeding supplemental oils to reduce grain consumption can also decrease risk factors for a number of gut problems.

It’s also important to ensure you are providing your horse with free-choice loose salt and adding 1-2 tablespoons of salt per day to your horse’s ration.

Salt consumption helps to encourage water intake, which can help to buffer against gastric acids. Hydration also promotes the transit of food through the gastrointestinal tract.

Several safe and natural nutritional supplements have also shown benefits for gastric ulcers.

Ulcer supplements may work by supporting gut barrier function, promoting overall digestive health or by supporting tissue repair.

Some ingredients that have research-based evidence to support their use include:

Pectin-Lecithin complex: Exerts a mucous protective effect that may be beneficial for both squamous and glandular ulcers ^[28]^[29]

Yeast: A probiotic that may help reduce the risk of squamous ulcers ^[30]

Amino Acids: (i.e. glycine, glutamine) Involved in the building and repair of tissues in the stomach lining ^[31]^[32]

Sea buckthorn berry extract: Its high antioxidant content may be beneficial for EGGUS ^[33]

Visceral+

Mad Barn’s Visceral+ is a pelleted supplement that provides nutritional support for your horse’s digestive system, including support stomach health and the hindgut.