How much hay will I need to feed a horse in Florida - with no gr?

I had a large mare who had been starved and she ate a bale and a half a day. Also, I gave her a quart of oats in the morning and at night. She gained weight good and got healthy. Part of that hay ended up in her stall under her feet, but at least I knew she had plenty to eat. Arabians eat about a half a bale a day, from what I've been told, but they are smaller animals than the average American horse, too.