A large percentage of all horses suffer from either stomach, duodoenal or colonic ulcers at one time or another. The causes are varied but are often the result of the following:
Non-steroidal, anti-inflammatory drugs
These drugs, commonly given to horses lead to “right dorsal colitis”, a condition of ulceration and inflammation confined to a specific region of the large colon in horses.
The type and amount of roughage play a role in ulcer development. Roughage, because it requires more chewing, stimulates the production of more saliva. The swallowed saliva helps to neutralize stomach acid. There is an increase in acid production when concentrates are fed.
Horses evolved to graze, eating many small meals frequently. This way, the stomach is rarely empty and the stomach acid has less of a damaging effect. If horses and foals do not eat frequently, the acid builds up and ulcers are more likely to develop.
Amount of exercise
As the amount of exercise increases, there is often a change in feeding (e.g. more times of fasting, less roughage), which increases the risk of ulcer development. In addition, exercise may increase the time it takes for the stomach to empty, so large amounts of acid can remain in an empty stomach for a prolonged period of time.
Stress itself may decrease the amount of blood flow to the stomach, which makes the lining of the stomach more vulnerable to injury from stomach acid. Factors that can also influence the formation of ulcers are transportation, frequent competitions and unfamiliar surroundings.