Ulcer
The equine stomach is different than humans such that there is a glandular and a non-glandular portion. There is a normal protective mechanism of the non-glandular lining to prevent damage from stomach acid secreted from the glandular portion. When a horse is under high-stress situations or on a high carbohydrate diet, both of which are common with athletic horses, this innate protective mechanism fails, causing damage to the lining, resulting in ulcers. This is different from ulcers in foals, which usually acquire ulcers in the glandular portion of the stomach.