Try Starting Gate (or food grade lecithin from Bulkfoods.com – same thing. One cup/day; 1/2 AM, 1/2 PM/1100 lb. horse). Also free choice hay when stalled and plenty of pasture when turned out. One to two flakes of alfalfa (or 2-3 double handfuls of well-soaked alfalfa cubes) immediately prior to riding also helps. If you haven’t already, checkout Lunatunesfreestyles.com, DePaoloequineconcepts.com and Gettyequinenutrition.com – all have great ulcer information.