UlcerGard Oral PasteULCERGARD works to prevent stomach ulcers in horses. The active ingredient in ULCERGARD, omeprazole has been extensively tested for safety and effectiveness. Stomach ulcers are more common in horses than once believed. Studies have demonstrated stomach ulcers in over 90% of racehorses and 60% of performance horses in various disciplines. Horses secrete acid in their stomach 24 hours a day. Horses on grass pasture or eating large quantities of roughage