In simple terms, gastric ulcers are found in the horse’s stomach while hindgut ulcers are found in the hindgut (or specifically the colon and cecum).
The foregut of the horse comprises of the esophagus, stomach, and small intestine. This is where gastric ulcers occur.
The main types of gastric ulcers are:
- Squamous ulcers: Squamous ulcers affect the squamous portion of the horse’s stomach, which is the upper third of the stomach.
- Glandular ulcers: Glandular ulcers affect the lower section of the horse’s stomach.
- Pyloric ulcers: Pyloric ulcers appear at the opening from the stomach into the small intestine.
The hindgut consists of the horse’s large intestine, which includes the caecum, large colon, small colon, rectum, and anus.
- Right dorsal colitis: Ulcers can occur in any section of the large intestine, however the most common affliction is known as ‘Right Dorsal Colitis’. This area is this part of the large intestine, which is in contact with the right body wall. The main cause of right dorsal colitis is the use of non-steroidal anti-inflammatories, (like phenylbutazone) and hindgut acidosis.
- Hindgut acidosis: Hindgut acidosis occurs when the acidity of the horse’s hindgut is raised. This is caused by large quantities of undigested simple carbohydrates reaching the hindgut and producing lactic acid. The increase in acid reduces the hindgut’s mucous production and leaves the mucous membranes vulnerable to ulceration. In addition, the change in pH cause the ‘good’ bacteria die off.