Dont get me wrong about using other feeds that are balanced nutritionally, I have nothing against them, each to their own and for a short while we fed Purina Foal Ration etc. etc. when we had a larger show string and halter horses. We ultimately went back to whole oats because we felt safer feeding them to halter horses as the protein was lower, we could feed a bit more safely to bulk out our horses and the starch was more digestible. Of the 35 years we have been in horses only about 5 were spent feeding pelleted or premixes. We had 18 horses not including our foals, never had a case of collic, never had a founder, never had a single issue related to feed such as ulcers.
The mare we bought about 7 months ago had a tramatic injury to her front foot. She had blown an abcess out her coronet, she was 150 pound underweight, she was scarred up and marked up like she was in a world war. The safest feed for her was whole oats, there is no digestibilty problem, we could start her out slow and increase her a bit daily until she was optimium weight and I personally knew we would not collic on oats. She is now almost to the weight we think is perfect, she has a beautiful shinny coat and is coming along nicely with ground work and started lightly under saddle. We are feeding her a controlled amount of alfalfa because it contains calcium etc that the oats doesnt and balances out her diet. There are some excellent articles about feeding oats (whole) and alfalfa hay to your horses..some at Ag Canadas website under Albertas Horsefeeding Myths and Misconceptions and the Kentucky Equine Research Center also has some excellent articles.