[Walter]

All depends on the horse.

In general, a horse will eat 2% of his weight in hay a day. So if you have a 1000lb horse, he will eat roughly 20lbs of hay. An average square bale (in my area) weighs 50lbs. so about 1/4 to 1/3 of a bale a day.

None of that takes into consideration the moisture of the hay, what type of hay it is, the age and condition of the horse... Talk to someone who is knowledgeable about the horse you are going to buy (preferably a trusted trainer) and go from there.

I agree, it all depends with the horse. When I was young out horse used to eat 1/4 a day.