Rye is a great winter forage for horses. You do have to be careful, in my experience, when it comes up, it comes up green and lush FAST. I'm VERY conservative with putting the horses on it. I have big enough fields that it usually gets to the point where it goes to seed (the horses don't keep it down fast enough), and again, I have to be VERY careful. It's funny to watch them eat it, they go right along the tops and bite off just the seeds. Tastes great, but could easily founder a horse if they eat too much. I sometimes do the math and for us, it's actually cheaper to feed round bales than to do the seeding with annual rye. It is so nice to have green fields for so much of the year though!