My QH 17 yr old mare is currently getting 20 lbs of grain a day for the past 2 weeks or so. 10lbs in the morning and 10 in the evening. She is getting 5 lbs of senior diet and 5 lbs of a fat supplement pellet in order to gain weight to make up the 10 lbs for each feeding. She has been on the senior diet forever but the fat supplement was gradually added about a month ago because she was losing rather than gaining weight just as the harsh winter is about to start.
She has free (theorectical) access to grass round bale during the day but gets shoo-ed away a lot by other horses and gets 2-3 flakes of mixed clover/alfalfa at night.
She is finally gaining weight but the barn owner is worried about laminitis. She also gets a weight gaining powder supplement from Smart Pak too that was added before the fat supplement. She was on that for weeks before I made the decision to add the supplement.
I don't believe she has ever founded. At least it doesn't look like it. I've only had her for 6 months or so. She is wormed regularly and the vet has checked her teeth and they are good. She is a very efficient eater...doesn't spill any of her grain anywhere.
And, of note, she acts like she is starving when it is grain time, even now that she has gained back a little. For example, she started pulling against the cross ties when she saw the grain was being made just several feet down the aisle in front of her the other day. She nickers when she sees food or even when I lean down to give her a treat. I've never seen a horse with such an appetite actually.