Ulcers in horses: Why and what to do?

Endoscopic procedure reveals nearly 90 per cent of examined racehorses and up to 60 per cent of performance horses have gastric ulcers. Many trainers discuss with their veterinarian or nutritionist that their horses are just not performing, not eating up and just don't look right. The problem, pure and simple, could be gastric ulcers. The story is not unique it can be told for an estimated 90 per cent of racehorses. They are suffering from equine gastric ulcer syndrome (EGUS) -an ulceration of the esophageal, gastric or duodenal mucosa. Other performance horses used for showing, and even some pleasure-riding horses, may have an incidence ranging from 37 per cent to 60 per cent. Even more important, this syndrome doesn't affect only the equine athlete. Studies have shown that all horses are at risk, from newborns and yearlings, with occurrence rates of up to 50 percent.

How do gastric ulcers develop

Horses differ from humans because they secrete stomach acid continuously, even when not eating. Adult horses secrete 30 liters of gastric acid daily. When horses are unable to access food on a continual basis, such as when grazing, the pH balance of the stomach changes drastically and gastric juices begin to attack the stomach mucosa. Acid produced in the stomach is generally buffered by saliva which contains a high concentration of bicarbonate and mucus. If access to feed is reduced then consequently the saliva production is greatly reduced. As a result the squamous portion of the horse's stomach, the most common part to be affected, lacks the buffer bicarbonate and protective mucous coating to protect the stomach lining from acid. Various feed stuffs produce different amounts of saliva, for example 1 kg of hay takes 3000 chewing movements and produces 4 liters of saliva versus 1 kg of grain takes only 1000 chewing movements and produces 2 liters of saliva.

Causes for ulcers in horses

Diet and feeding behavior are known to affect the occurrence of gastric ulcers. Horses on pasture have the lowest incidence of ulcers compared to those athletes that need "high-energy" concentrates (a smaller portion of their diet is hay). Thus, it is believed the increased rate of ulcers in horses is due to a combination of factors including:
  • A high-concentrate diet with low-roughage intake (especially when only fed once or twice a day)
  • Withholding feed during competitions and intensive exercise on an empty stomach. Exercise Exercise is shown to reduce blood flow to the stomach lining as well as increasing abdominal pressure which may cause gastric compression, in turn forcing acid contents into the proximal stomach
  • Other factors which induce a stressful environment including physical stress such as illness and behavioral stress such as stall confinement, long-distance transportation, unfamiliar environments
  • Use of Non-Steroidal Anti-Inflammatory Drugs (e.g. Phenylbutazone or Flunixin meglumine

Clinical signs of ulcers

Clinical signs are vague and are not unique to gastric ulcers but fit many of the common complaints veterinarians hear from owners and trainers. These include: Adult Horses Poor appetite, Colic, Decreased performance, Attitude change, Poor body condition and Weight loss Foals Intermittent nursing, Poor appetite, Intermittent colic, Poor body condition, Diarrhea, Teeth grinding, Salivation, Pot belly and rough hair/coat However, owners and trainers should be suspicious of Ulcers if any or all of the signs are observed or reported in the horse.

Diagnosing Ulcers

There is only one sure way to confirm ulcers, Esophagogastroscopy, or simply "stomach scoping," is the only means to prove whether ulcers exist or not. No food is to be fed six to eight hours before scoping. A light sedative is given five minutes before the passing of the three-meter scope, similar to passing a stomach tube, down the horse's esophagus. It is extremely common that the horses scoped have severe ulceration of the squamous part of the stomach area where 80 percent of the ulcers are found in adult horses. The severity of stomach ulcers is rated in grades from an inflamed but intact epithelium (Grade 0 ulcer), superficial erosions of the mucosal surface (Grade 1 ulcer) to single superficial erosions of the mucosal surface (Grade 2 ulcer) to multiple actively hemorrhaging hyperemic (Grade 3 ulcer).

How do we treat Ulcers?

Now that the condition of horses is known, how is he to be treated? The acid pump in the horse's stomach producing gastric juices needs to be suppressed. Pasture and free access to hay is the most natural and least ulcerogenic environment. Forage consumption not only slows speed of feeding, but also stimulates saliva that acts as a protective buffering agent. Racehorses and performance horses generally heal faster if removed from training and competition. Horses with documented gastric ulcers have responded to histamine H2-receptor antagonists, such as cimetidine and ranitidine, commonly known as H2 blockers. Although H2 blockers may provide limited, symptomatic relief, they block only one of several sites that stimulate acid production and may not heal the underlying gastric lesion. Antacids need to be given every two to four hours in a volume of 200g at each treatment to be effective. A newer approach to the treatment of gastric ulcers is the introduction of the proton-pump inhibitors, also referred to as the acid-pump inhibitors. This is the "gold standard" for ulcer treatment in humans and promises to be a cure for ulcers in horses. The major advantage is this treatment has the same active ingredient, omeprazole, as in human ulcer medication. Administered daily, the acid-pump will effectively block the production of gastric acid throughout the 24 hours after administration. The only problem that arises with the use of these products is that they have to be taken off these medications prior to competition. This increases the risk of the ulcers reoccurring or not healing properly and thus will affect performance. For the holistic person several herbs have been used to aid in the treatment of symptoms of ulcers in horses. Comfrey leaf, Marshmallow Root, Liquorice, Meadowsweet and Slippery Elm have all show signs of mucilaginous properties, which aid in providing a mucous layer over the stomach lining. One thing to point out is that they have not been proven on horses yet. Please remember herbal preparations do not work as quickly as prescription drugs so if you choose an alternative therapy to treat your horse give it time to work. Also consult your veterinarian with respect to the treatment you are giving your horse as some preparations may negatively interact with other medications you may be treating your horse with.

Prevention of Ulcers

  • Avoid long periods without food and feed frequent small meals.
  • Feed ad lib hay - if feed is withheld the pH in the stomach drops to 2 in 21 hrs
  • Place feed bins on the ground to simulate the horse’s normal grazing position as it helps his chewing action, stimulating the production of more saliva which in turn helps the passage of food to the stomach.
  • Feed a small amount of lucerne chaff prior to work as Lucerne chaff helps in two ways by acting as a physical barrier and secondly the calcium in the Lucerne binds the acid.
  • Do not exercise on an empty stomach as this allows acid to attack the stomach wall when it is empty. Feed a small amount of Lucerne chaff 30 minutes before exercise.
  • Avoid physical and behavioral stress.
  • Avoid long treatments with non-steroidal anti-inflammatory drugs such as Phenylbutazone.
  • Allow the horse to walk around and self-exercise and graze as if he would in the wild, this way he always has feed in his stomach.



Equine Gastric Ulcer Syndrome is a major cause of underlying illness in performance horses and therefore impacts the health and performance of the horse. Make sure the horse’s diet includes access to pasture, adlib hay and highly soluble fiber sources especially if they are stabled to allow them to produce the required amount of saliva to buffer the stomach acid produced. Reduce or remove stress factors affecting the horse and seek treatment from your veterinarian. Remember effective treatment entails environmental, behavioral and dietary management as well as medical intervention.

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