How much does your horse and bales of hay weigh? Is your horse an easy orhard keeper? I believeyou can go down to 1.5% of their body weight daily for a horse who needs to loose weight. My 15.2 hand 1100 lb or so horse eats 2% of her body weight when healthy weight, so 22 lbs for her. I brought about 300 lbs for her when she blneeded to lose weight when I was trialing her for two weeks - came back with 15 or so lbs. A safe amount is about 2% of their body weight which for an average 1000 lb horse would be 20 pounds. So for one 60 lb grass bale that would give that 1000 lb healthy horse about 3 full days of feeding, 20 lbs each day. Alfalfa you shouldfeed less of as its so rich but because you are feeding little of it the horse would finish it off faster and be without hay longer. I know of some horses will eat up to 4% that are hard keepers that need to gain gain weight or haft to have it to maintain weight. It is of course, better to be safe than sorry.