Sorry missed the bit about the alfalfa
Over acidity is treated with calcium carbonate but I'm not sure if the calcium content in food can break down or combine to produce that. Certainly a high fibre diet is vital for horse with ulcer problems and sugar beet (non mollassed) is a great source of fibre and calcium and horses that do suffer should never be left for long periods without food
There are lots of things you can buy without prescription for ulcers now - take a look on Smartpaks website to get an idea,
I found this youtube channel that is quite helpful a while back when me mare had ulcers after being on Naproxin for a while. She was treated with Omeprazole initially and then ranitidine and I kept her on Absorbine Pro CMC for a few months afterwards. She is fine now.