Equine Ulcers

This was a fact sheet that I did on Equine Ulcers for my Equine Nutrition class through Guelph University. 



      Equine gastric ulcer syndrome (EGUS) is extremely common in horses and foals. It is most commonly associated with performance horses (~ 60% contract it) due to the changes in natural social and housing needs. EGUS is seen predominately in racehorses who are not on preventative treatment for it (~90%). EGUS is the presence of ulcerative lesions affecting the tissues of the esophagus, stomach and entrance to duodenum. The majority of ulceration cases affect the non glandular region of the stomach referred to as the squamous mucosa (8). This problem is relevant to this course and my personal equine experience because of how common of a problem this is with performance horses as well as how it affects the overall nutrition and physical and mental health of the horse. The presence of gastric ulcers and the prevalence of them is direct evidence of the unnatural living conditions in which horses tend to be kept and cared for in the performance world (2).

       The general consensus is that excess acid, bacteria and stress are the main contributing factors to EGUS, but it is not currently known for certain exactly what contributes to ulcers in horses. Because horses are always producing acid, their stomach should not stay empty for extended periods of time. As horses have developed alongside humans over the years, their digestive systems have not changed to adjust to our modern day feeding strategies. Horses have remained trickle feeders, meaning that their bodies are meant to be grazing throughout the day and their stomachs are to be consistently intaking small amounts of food throughout the day (3).

      Due to how common this particular ailment is, knowledge of EGUS is relevant and important to this course itself as well as horse owners and horse handlers worldwide. While this problem isn’t typically deadly, it causes a lot of discomfort and can decrease the performance and health of horses greatly. Understanding the equine digestive system, how it works and why it works the way it does is essential to understanding EGUS. This problem is relevant to my personal life due to my presence in the racing industry for my job, my life as a horse owner and my experience rehabbing and reselling off the track Thoroughbreds. This is a problem I have witnessed frequently and have had to deal with my personal horses.

Clinical Signs

The majority of horses afflicted with gastric ulcers will not show outward clinical signs.The symptoms are often more subtle, such as the following:

  • Poor appetite
  • Dullness of coat
  • Changes in attitude
  • Decrease in performance
  • Reluctance to train
  • Weight loss
  • Frequent low grade colics
  • Loose feces
  • Poor body condition
  • Recumbency
  • Discomfort during brushing or tacking
  • Aggression during saddling

More serious cases of ulcers will also be symptomatic with colic episodes and/or grinding of teeth. In serious cases, some horses may even be found on their backs (most common in foals) as this can provide some pain relief in the case of acute gastric ulcers (7). Other signs of more severe cases of ulcers are seen in horses who will walk away from their food for a period of time as discomfort increases when the food first enters the stomach (2).

The clinical signs of EGUS in foals are: intermittent colic (seen after eating or drinking milk), laying on their backs frequently, interrupted nursing due to discomfort (for same reason adult horses will walk away from food in the case of ulcers), diarrhea, poor appetite, teeth grinding and excess salivation. If a foal exhibits these clinical signs,the case is likely to be severe and treatment should ensue immediately. The only definitive way to diagnose ulcers is for the vet to perform a gastroscopy of the esophagus and stomach. Palpating is a less accurate way to diagnose but can be helpful (2).

While using these symptoms to determine whether or not your equine suffers from EGUS can be useful, it is not always accurate. Horses who have mild to moderate ulceration may exhibit all or most of these symptoms, while severely ulcerated horses may exhibit none (3).


   While the exact causes of ulcers are not fully known, research has shown what the probable causes are. Horses are constantly producing stomach acid, and because of this, the stomach lining needs to be protected with a steady supply of both saliva and forage. As our use of horses has evolved, so have modern day feeding practices. These practices generally consist of feeding large meals 2-3 times per day, which leaves the stomach empty for long periods of time,  increasing the lining’s vulnerability to being damaged by these acids. Exercise can also exacerbate this by moving the acids around the empty stomach and pushing them into the sensitive upper portion of the stomach (1).

   Parasites such as botflies are also a cause of ulcers. The larvae of parasites are easily consumed by horses (8). Botfly larvae can live inside a horse’s stomach and create holes that, with consistent irritation from stomach acid or the introduction of bacteria, can become gastric ulcers. New studies show that bots are becoming a larger problem as they become more resistant to worming treatments due to routine worming regimes without checking fecal egg counts (1).

    In conjunction with certain feeding strategies causing ulcers, stress is also a contributing factor. The way many choose to keep and stable their horses in the modern day increases stress levels. Horses are grazing, free roaming animals who are meant to wander and forage throughout the day. Excess stabling causes stereotypies such as cribbing, weaving, stall walking and wood chewing. All of these are outward signs of boredom and stress and are thought to contribute to ulcers due to the release of the stress hormone Cortisol lowering the pH of the stomach and thus increasing the risk of ulcers.

It is also said that certain breeds such as Thoroughbreds and Standardbreds may be predisposed to ulceration, however, there has not yet been any correlation in age or sex in the majority of studies performed. Some say that increasing age in turn will have an increased effect on the severity of ulcers, but there are no conclusive findings regarding this (6).

Management Strategies

Treating ulcers starts with the prevention of them in the first place. In order to prevent ulcers, most people will need to rethink their feeding and stable management strategies. Knowing that having an empty stomach will increase the amount of acid in the stomach, thus making the horse prone to developing ulcers, horse owners must take steps to ensure the horse has access to forage throughout the day (9). This can be offered in several different ways. Many people opt to free feed forage via a round bale of hay, flakes of hay thrown to replenish throughout the day, allowing the horse to graze 24/7 on a grass pasture, or using slow feed hay nets and other devices to slow down the intake of forage and allow the horse to trickle feed without having to increase the volume of forage. Ample turnout will also reduce stress, which is a contributing factor to ulcers (5). Studies have also shown that turnout allows for more movement, which in turn will help with digestion and reduce risk of other digestive ailments such as colic. Studies have also shown that turn out with other horses appears to reduce risk of ulcers due to reduced stress from being allowed socialization (6).

The use of processed feeds also increases risk of ulcers, another reason why modern day diets high in processed grains (more common in performance and sport horses) increase the risk of ulcers due to the larger feedings fewer times a day. Offering horses high fibre material consistently throughout the day allows their stomachs to be full near constantly, thus reducing the risk of excess acid creating ulcers (4). To avoid acid splash (build up of acid in the stomach moving and causing irritation during exercise), feeding of forage about fifteen minutes prior to exercise is recommended. This could just be a flake of hay or a small amount of soaked hay cubes to coat the stomach and prevent irritation. Alfalfa is said to be useful in coating the stomach so chopped alfalfa cubes are recommended (8).

The only current FDA approved treatment of ulcers is Gastrogard. Gastrogard is the brand name for a medicine called omeprazole, which is also used in humans for ulcers. Gastrogard works by inhibiting the proton pump that produces stomach acid, meaning it allows the stomach to produce enough acid to digest food but not enough to create an excess build up of acid that is a major factor in causing ulcers. Gastrogard is typically used in a full dose of 2.28g per day for 28 days. Many vets will also recommend tapering the dose off for an additional two weeks until the horse is weaned off the omeprazole. Gastrogard also has a preventative treatment called Ulcergard which works by being used in smaller doses during times of stress (such as travel, showing, moving barns, stall rest, etc) to help prevent the reoccurrence of ulcers (5).


Take Home Points 


  • Allow for constant access to forage (grass, hay, chopped hay cubes) throughout the day in order to keep stomach full and reduce risk of excess acid build up.
  • If constant access to forage is not feasible, the use of a slow feed mechanism such as a small-holed hay net in order to slow the intake of feed down should be used. 
  • Reduce stress levels by allowing horses frequent access to turn out and limit stalling in order to avoid release of the stress hormone Cortisol, which is said to lower pH of stomach.
  • Use Ulcergard as a preventative prior to stressful or new situations that may increase the risk of developing ulcers which can occur in less than 5 days. 
  • Limit the amount of process grains that are fed. Try to split large grain-based meals into smaller, more frequent meals. Stay away from grains like corn. 
  • In foals, speak to your veterinarian about ways to prevent the occurrence of ulcers during stressful times such as weaning.
  • Have horses who are displaying potential symptoms, or who have been used in an industry such as racing where ulcers are extremely common, scoped and treated as needed prior to the problem getting out of control. 
  • Gastrogard is the only FDA approved treatment for ulcers in horses.
  • Ulcergard is Gastrogard’s other ulcer medication that is to be used for prevention only, not treatment.
  • Avoid acid splash during riding by ensuring the stomach is coated and not empty. Alfalfa cubes are a good option for this.
  • Be conscious of your horse’s outward condition and how comfortable they are during tacking and riding. Work alongside your vet to keep an eye on your equine and lower risk of developing or redeveloping ulcers.







  1. http://www.succeed-equine.com/education/gi-health-care/health-risks/equine-gastric-ulcer-syndrome/
  2. http://www.vetmed.ucdavis.edu/ceh/local_resources/pdfs/pubs-Oct2012-sec.pdf
  3. http://www.clydevetgroup.co.uk/equine/newsletters/apr07.htm
  4. http://www.drsfostersmith.com/pic/article.cfm?aid=1587
  5. http://www.ulcergard.com/treat-with-gastrogard/Pages/default.aspx
  6. http://www.horsetalk.co.nz/2015/09/07/specialists-gastric-ulcers-horses/#axzz3m2CTIBe2
  7. http://www.thehorse.com/articles/36028/gastric-ulcer-prevalence-in-feral-domestic-horses-compared
  8. http://www.merckvetmanual.com/mvm/digestive_system/gastrointestinal_ulcers_in_large_animals/gastric_ulcers_in_horses.html
  9. http://www.vetmed.ucdavis.edu/ceh/local_resources/pdfs/pubs-Oct2012-sec.pdf