Gastric Ulcers in Horses

Jennifer Rice, DVM
By Jennifer Rice, DVM on Oct. 28, 2022
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What Are Gastric Ulcers in Horses?

Gastric (or stomach) ulcers in horses is a common concern as it can affect any horse at any age, causing mild to severe disease. Ongoing, active research shows that up to 90% of racehorses and 60% of show horses, as well as non-performance horses and foals are affected by gastric ulcers. In recent years, studies show that most horses may not even exhibit outward signs when dealing with stomach ulcers. 

A horse's stomach can be divided into two parts, glandular and non-glandular. The bottom part of the stomach is the glandular region where stomach acid is produced and created to help with digestion. The top portion of the stomach is non-glandular or the squamous portion of the stomach. The squamous portion is where most of the mixing of the food happens and is the most common site of ulcer formation. Unlike the glandular region that has a protective coating to help prevent damage from stomach acid, the non-glandular or squamous region does not have this coating. Because of this it is much more prone to damage from the stomach acid–thus producing stomach ulcers.

Unlike humans that only produce stomach acid while eating, horses are constantly producing stomach acid as they are meant to eat small portions of food at a time and constantly graze. Horse stomachs produce up to 9 gallons of acid per day, even when they are not eating.

Symptoms of Gastric Ulcers in Horses

Signs your horse may be suffering from ulcers include:

  • Poor appetite 

  • Weight loss or loss of body condition

  • Lethargy or dullness

  • Behavior change—especially grumpy/irritability about being saddled or ridden

  • Diarrhea

  • Poor hair coat

  • Grinding of teeth

  • Poor performance

  • Acute or recurrent colic, particularly after eating

  • Frequent lying down

  • Reluctant or slow to eat grain

  • Frequent episodes of being cast or stuck in stall—some horses (especially foals) get pain relief from ulcers by laying upside down

Causes of Gastric Ulcers in Horses

Gastric ulcers have been said to be a “man-made disease” in horses, meaning that we have caused ulcers in our horses today by changes in lifestyle and feed that are not natural for the horse. Many factors can contribute to ulcer formation in horses, from feeding them in a less conducive way to their natural anatomical structure, to keeping them in stressful environments such as stalls and traveling. Factors that can lead to ulcer formation include:

  • Stress 

  • Stall confinement 

  • Chronic administration of medications, especially NSAIDS (i.e., banamine and bute)

  • Feeding large grain meals

  • Prolonged periods of no roughage 

  • Traveling 

  • Heavy exercise or workload

How Veterinarians Diagnose Gastric Ulcers in Horses

To diagnose gastric ulcers your veterinarian will start with a history and physical exam. If your veterinarian believes gastric ulcers could be affecting your horse, they will likely recommend a flexible endoscopy of the stomach as this is the best way to diagnose ulcers in horses. This procedure can be performed on the farm, at a veterinary clinic, or hospital. The horse is commonly given mild standing sedation and a twitch is placed on their nose. During the procedure, a three-meter fiberoptic scope is placed in the horse’s nose and passed through the esophagus into the stomach. The veterinarian will be able to visualize the surface of the stomach through a camera to look for any ulceration of the lining. Most horses tolerate this procedure very well with little to no side effects.

Some preparation is involved with endoscopic procedures so that the veterinarian can visualize the stomach. Your veterinarian will provide the necessary guidelines before the procedure, but these generally include:

  • Withdrawal of food for at least 12 hours before the procedure

  • Removing water 3-4 hours before procedure

  • Some horses may require further fasting

Treatment of Gastric Ulcers in Horses

Depending on the severity of the ulcers, treatment is aimed at removing the predisposing factors and decreasing the acid production to allow ulcers to heal. Currently, there is only one FDA-approved pharmaceutical treatment for ulcers—omeprazole.

Omeprazole for horses is available as a prescription paste formulation called GastroGard which has been effective at the treatment and prevention of gastric ulcers in all horses. GastroGard works by reducing the production of stomach acid by inhibiting (suppressing) the proton pump within the stomach that secretes stomach acid. Treatment with GastroGard is recommended to be given once a day for a total of 28-30 days. A recheck endoscopy is generally recommended to monitor the progression of healing.

Recovery and Management of Gastric Ulcers in Horses

Successful recovery and management of ulcers may require GastroGard, but also environmental, lifestyle, and feed practice changes to reduce a horse's stress. Prognosis is generally very good for horses with ulcers. Tips for quick recovery include the following:

  • Allow free-choice access to grass or hay. Horses are meant to be grazing all day with a constant intake of roughage. 

  • If a horse must be stalled, allow horse socialization by being near other horses or offering stall toys such as a ball.

  • Providing daily turnout time even if it must be in an arena or dry lot can help reduce a horse's stress significantly.

  • Feed small, more frequent meals to help aid the buffering of constant stomach acid.

  • Decrease grain meals or high concentrates that form volatile fatty acids. These feeds are generally higher in carbohydrates such as sweet feeds.

  • Avoid or decrease frequency of any anti-inflammatory medications when possible.

  • Limit stressful situations such as high-level training or frequent traveling.

Gastric ulcers can lead to more severe symptoms or disease including:

Prevention of Gastric Ulcers in Horses

Treatment for gastric ulcers as listed above also serves as effective prevention.

If your horse is prone to ulcers due to their unique lifestyle or environment, your veterinarian may discuss keeping your horse on an over-the-counter medication called Ulcergard. Ulcergard is given daily and is a half dose of GastroGard. It has been shown to help with prevention of ulcers for some horses.

Digestive or calming supplements may also be recommended by your veterinarian to help with prevention of ulcers depending on your horse's lifestyle and personality. 

Gastric Ulcers in Horses FAQs

What do horses do when they have ulcers?

Most commonly, horses show no outward symptoms or have very subtle changes in behavior such as teeth grinding, attitude changes, decreased appetite, or poor performance. 

What is the best thing for ulcers in horses?

Prevention is the best practice for ulcers. Make sure to provide your horse with a happy, low-stress lifestyle by providing daily turnout and socialization as well as good feeding practices.

What is a squamous gastric ulcer?

Squamous gastric ulcers are ulcers that form on the non-glandular part of the stomach and are the most common type of stomach ulcers. 


  1. AAEP. Equine Gastric Ulcers: Special Care and Nutrition. 2016.

  2. University of Minnesota Extension. Stomach ulcers in your horse.  

  3. Penn State Extension. Using Nutrition to Manage and Prevent Stomach Ulcers in Horses.

  1. ‌‌Young A. UC Davis School of Veterinary Medicine. Equine Gastric Ulcer Syndrome. 2019.

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Jennifer Rice, DVM


Jennifer Rice, DVM


Dr. Jennifer Rice is a 2017 graduate from Purdue College of Veterinary Medicine where she specialized in Equine medicine. Since graduating...

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