Ulcers are rife in horses. A recent survey from a group of equine experts and veterinarians in the USA concluded that 87% of horses have ulcers. Ulceration in the fore and hind gut of a horse can cause considerable pain to the animal and often makes it behave erratically. Ulcers occur because for several reasons. The cause is usually a change of diet, rapid grass and pasture growth and general stress.