OP, you could also start treatment with ranitidine, but it's a hassle. Ideally it's given 3x a day, but my vet has given me the OK to administer 2x day. The pills should be crushed or ground and given orally. But ... it's cheap. My vet called it in to Costco.
Before we got my mare's ulcers under control, it was very difficult to keep weight on her, especially in the winter. She just wasn't interested in food. But now: mostly alfalfa hay (in small-hole hay nets), soaked alfalfa cubes, ground flax, oil and Purina Wellsolve Low Starch - her weight is better than any of the previous 4 winters.