Lovely pictures. I'm so glad Solon posted. She's always right on the money with draft advice. Personally, I only use straight alfalfa hay for treats. We use mixed grass for the bulk of our winter feed.
I've got my whole crew on grass hay, in part because it's not good for my draft or my fat pony :) The other two, a paint and a Hanoverian filly do just fine, in fact the filly is so much more sane off alfalfa!!