How do you know your horse has ulcers?

1. Physical signs: Some horses with ulcers have a poor coat, and struggle to gain weight despite adequate feeding. Ulcers have also been implicated as a cause of recurrent episodes of colic. Horses (particularly foals) with severe ulcers sometimes grind their teeth. 
2. Behavioural signs: Ulcers have been associated with changes in temperament, picky eating behavior or periods of going off feed. Some studies have shown an association with ulcers, reduced time to fatigue, reduced stride length and poor performance. Horses may also show sensitivity on their abdomen, particularly around the girth area and may resent being brushed. There may also be a link between ulcers and crib biting. 
3. Gastroscopy. To date, direct visualization of the ulcers in the stomach using a 3m endoscope remains the only reliable method to diagnose presence or severity of ulcers. The procedure will be discussed further along in this article. 

Tolerance and outward signs of ulcers will vary considerably between horse does. In thoroughbred racehorses, rates of 37% of spelling horses and 80-100% of horses in training have been reported. Rates of 54% in pleasure horses and 64% of sport horses have also been found in some surveys. The lowest prevalence was 11% in horses being ridden at home and not competing.  Ponies who are on feed restriction for weight loss are at a high risk if they are not able to chew continuously.