Gastric ulcers are extremely painful and unfortunately all too common in the domesticated horse, particularly in performance animals. It has been estimated that 80-90% of all Thoroughbred racehorses suffer from gastric ulcers.

The signs of gastric ulcers are often non-specific but can include:

  • Colic
  • Reduced appetite
  • “Tucked-up” appearance
  • Poor condition
  • Unthriftyness
  • Intermittent diarrhoea
  • Poor performance

The horse’s stomach

To understand why gastric ulcers occur, we must know how the horse’s stomach works. The horse’s stomach is divided into two distinct regions:

The upper region is described as squamous, non-glandular epithelium. It is not protected by cells and should be alkaline. The only protection the upper region of the stomach has from acid is the buffering effect of saliva.

The lower region is described as glandular epithelium and is protected from acid by mucosal cells and stomach lining. HCl (acid) is continuously produced in this part of the stomach, regardless of whether the horse is eating or not. This means that the acidity of the stomach if it has not received food for 8hrs can be so strong that it would remove the skin from your hand.

Ulcers do not occur in the epithelial layers of the lower part of the stomach. Gastric ulcers in horses are found most commonly at the junction between the lower and upper part of the stomach in an area known as the margo plicatus. They occur when the acid production exceeds the protective factors.

Saliva protects the upper part of the stomach and the margo plicatus. During normal trickle feeding such as grazing enough saliva is produced to buffer any acid found in the upper part of the stomach. However, saliva is only produced when a horse is actually chewing and the amount produced varies according to the type of feed being fed.

Prostaglandin E protects the lower part of stomach by increasing blood flow to stomach lining, which aids repair, removes irritants and takes plasma to site of injury. Prostaglandin E also decreases gastric acid production reducing the risk of gastric ulcer formation. The lower part of the stomach is also protected by a mucosal bicarbonate layer, which lines the stomach buffering it from gastric acid.

Cause and treatment

Gastric ulcers can be caused by:

  • Infrequent and incorrect feeding
  • Reduced saliva
  • Stress

The ulcers can be managed by drugs from the vet and by making changes to the horse’s daily management. The drugs in common use include:

  • Cimetidine and ranitidine, which act to slow signals to acid producing cells but they do need to be administered at least three times per day.
  • An Omeprazole drug has recently been licensed in the UK. It needs to be administered once a day and is considered one of the more successful treatments

The most successful treatment for gastric ulcers is to turn the horse out to grass. This enables the eternal presence of acid to be cancelled out by the continuous presence of food. Because horses only produce saliva when they chew, and saliva is essential to protect the stomach from acid secretion, feeding to maximise chewing and saliva production will greatly reduce the risk of gastric ulcers.

Feeding tips to avoid ulcers

  • Increase fibre intake – the horse should have access to forage throughout the day and night
  • Use two small holed haynets, placed inside each other, to extend eating time
  • Place two haynets on either side of the stable
  • Feed chaffs such as Dodson & Horrell’s Alfalfa or Fibergy
  • Place large smooth bricks in the manger to slow down eating of hard feed
  • Feed little and often, starch-based hard feeds should be no more than 2.5kg in size (for a 500kg horse)

For friendly feeding advice call the Dodson & Horrell Helpline (tel: 0870 442 3322).