Pete,

Yes,

A horse should eat 1-2% of their body weight a day in roughage (hay) for maintence. So if you have a 1000lb horse (at 1% a day) then it should eat 10lbs of roughage a day broke into at least 2 feedings. So 5 lbs in the morning and 5 lbs in the evening. This is just a base line to start (typically those easy keepers), and I would go more with 1.5-2% so somewhere between 15-20 lbs of hay a day for most horses. You should really weigh all your horses feed, not just go by a flake. The easiest way to weigh hay is get yourself a hand held fist scale (about $5 at the store) and a hay net. Since the net weighs hardly anything, put 1-2 flakes of hay in the net and hook it to the fish scale and hold it up by the handle and see how much it weighs. Once you get a general feel you don't have to weigh it every time. Now this is for horses on little to no exercise. Breeding animals, youngsters and performance horses this will vary depending if you are feeding a grain supplement. Hope this helps.