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What are Ulcers?

Ulcers in horses affect many; almost half of all foals and one-third of adults can be affected by this condition. Moderate to severe ulcers commonly develop in horses of all types, and this condition is also known as equine gastric ulcer syndrome. It is also referred to as equine gastric ulcer disease. 

Horses are prone to ulcers because the horse’s stomach is very small. The horse’s stomach holds four gallons and has two sections. The esophageal region, or the non-glandular region, has a lining of tissue. The animal’s second section, the glandular portion, of the stomach produces hydrochloric acid, which is used to aid in food digestion. This acid is being produced within the horse’s stomach at all times, and if the horse doesn’t eat, or if the feed does not agree with the horse, then it builds up within the stomach. This acid affects the lining of the stomach and causes painful ulcers to occur. 

Horses must eat as they were designed, which is by grazing lightly throughout the day in the pasture. Horses that are workers or are being trained may be stabled and fed on the owner’s terms. Since horses are continuously secreting gastric acid, even when not eating, and a more “restricted” access to food rather than the freedom to graze cause too much acid build-up within the stomach. Horses that are able to eat clean hay and grass are less susceptible to this painful and irritating condition.

Ulcers in horses are periods of inflammation of the lining of the stomach. Ulcers develop from the build-up of hydrochloric acid within the stomach. Ulcers can range from mild to severe and require medical attention in order to be properly treated.

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Symptoms of Ulcers in Horses

If your horse is showing signs of an ulcer, make an appointment with your veterinarian. There are many different symptoms of ulcers; therefore, it is important to observe your horse and note any different signs or behaviors. Symptoms may include:

  • Colic after eating
  • Nursing or eating for very short time periods
  • Grinding of the teeth
  • Diarrhea
  • Drooling
  • Poor appetite
  • Weight loss
  • Behavioral changes
  • Lack of performance
  • Lying down frequently
  • Distress
  • Agitation, as if in pain


There are several different types of digestive ailments that can affect horses. Like ulcers, these conditions can cause pain and discomfort within the stomach and gastrointestinal tract. Types include:

  • Diarrhea
  • Colic
  • Rotavirus
  • Vesicular stomatitis
  • Potomac horse fever
  • Enzyme deficiencies
  • Obstruction in gastrointestinal tract
  • Excessive gas
  • Birth defects
  • Parasite infestations

Causes of Ulcers in Horses

There are several different causes of the development of gastric ulcers in horses. Ulcers can be very mild or quite severe. Causes can include:

  • Fasting
  • Inconsistent eating
  • Infrequent eating
  • Feed that does not allow the horse to produce saliva
  • Too much exercise
  • Stress increases the amount of blood flow to stomach
  • Overuse of anti-inflammatory medications

Diagnosis of Ulcers in Horses

If you suspect your horse has a gastric ulcer, make an appointment with your veterinarian. An ulcer can be serious, and sometimes fatal if medical attention is not given in time. Your medical professional will ask questions pertaining to his health history, look closely at his clinical signs, perform blood work, urinalysis, biochemistry profile, and other laboratory testing in order to rule out any other illnesses and come to a preliminary diagnosis.

Your doctor may perform specific diagnostic testing using enhanced diagnostic equipment. He may use a gastroscope, which is an approximately 2 meters-long endoscope into the stomach of your horse. This is currently the most accurate and definitive diagnostic test used to confirm the presence of a stomach ulcer or ulcers.

This test will confirm the specificities of the ulcers, such as size, severity, and precise location. Typically, ulcers are found in the upper portion of the organ; however, ulcers can also be found in the lower section, including the duodenum. The ulcer will be classified between the areas of 0-4, with a 4 having severe lesions. He will communicate with you the extent of the ulcer and let you know the options for treatment.

Treatment of Ulcers in Horses

Treatment of gastric ulcers in horses may vary depending on the severity of the ulcer. Treatment methods may include:

Acid Inhibitors

Specific acid inhibitors may be prescribed to your horse to treat his ulcer. Called Proton pump inhibitors, these prescription medications may be given by your veterinarian to decrease the amount of acid that the stomach is producing.

H2 Blockers

H2 Blockers are medications that may be chosen by your veterinarian to prescribe to your horse to block any histamine in your horse. Histamine encourages the stomach to produce more acid. Common histamine blockers are ranitidine and cimetidine.


Antacids are effective at blocking or “buffering” any stomach acid from affecting your horse. Antacids, though, are only effective for a limited amount of time. Your horse’s stomach is always producing acid, so large amounts (many dosages) are needed of this type of medication. If your horse is a performance horse, antacids may be beneficial to give sporadically, such as on the day of a performance. 

Changes in Lifestyle

Effective treatments for ulcers also include making changes to your horse’s lifestyle. This may include increasing feeding times throughout the day, putting your horse to pasture, lessening his intake of grain, adding supplements, increasing roughage in his diet, and administering probiotics to help his digestion.

Recovery of Ulcers in Horses

Once treatment is begun, ulcers tend to begin healing; however, it may take time. Depending on the type of treatment and the severity of the ulcer, your horse may take anywhere from a week to over a month to heal. Since ulcers tend to recur, it is important to have your horse get checked by your veterinarian a few days after the treatment is complete.

If you choose to give supplements or probiotics to your horse, be sure to consult with your veterinarian and he may give you professional advice on what would benefit your horse. Your medical professional will also reiterate the importance of altering his eating habits and stall time. 

Your veterinarian will give you specific instructions on the medication dosage and administration, and will communicate to you any side effects to watch for. It will be important to monitor your horse’s symptoms and behavior during treatment and after. If you have any questions or concerns about how your horse is recovering from a gastric ulcer, contact your veterinarian. He may want to see him again during his treatment period to check on his recovery.

Ulcers Questions and Advice from Veterinary Professionals

13 Years
Mild condition
1 found helpful
Mild condition

Had a vet check out my 13 year old Friesian mare. She seemed "frumpy" & didn't show any interest in her grain,(which she is always happy to be eating) - she looks like she has lost some weight, which is not a bad thing because she could afford to shed some weight, but not if she is losing it due to illness of course. Her living conditions are full turn out with shelter, there has been no change in her herd dynamics, food, or anything else for that matter. Vet checked her out, no temp. listened w/stethoscope ext. He did everything short of drawing blood. He gave her a clean bill of health. She has no discharge from eyes or nose. So my question is, am I missing something? She is a mare, they tend to me moody. Am I putting to much faith in the vet & everything I know about horses? No discharge, no temp, she sounded great. Our vet also mentioned he has had numerous calls from livestock owners of both horse & cattle, & that our crazy weather this year has really taken a toll on livestock this year, as we live in lincoln, nebraska. Friesian horses are a delicate breed. I am thinking possible lyme disease or ulcers? I just assumed there would be a fever, or secretion of some sort?

Dr. Michele King, DVM
Dr. Michele King, DVM
1611 Recommendations
Thank you for your email. Without examining Ella, I'm not sure that I can give you any more insight into her condition than your veterinarian did - if you are not sure that she is okay, it would be best to follow up with your veterinarian, as they can examine her, run blood work if necessary, and make sure that she is healthy.

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15 Years
Fair condition
0 found helpful
Fair condition

Has Symptoms

Loss of Appetite
Wood chewing (from time to time)

Medication Used


I was wondering if my mare having Ulcers was likely, based on the symptoms I have provided. Would she possibly have Ulcers? If not, what could possibly be another alternative?

Dr. Michele King, DVM
Dr. Michele King, DVM
1611 Recommendations
Thank you for your email. With the brief list of signs that you mentioned, there can be a number of possible causes. Without examining Rosie, I cannot comment on what might be going on. It would be best to have her examined by a veterinarian, as they can look at her, assess her physical health, and recommend any possible testing or treatments that might need to be given. I hope that she is okay.

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