QUestion please help me!?

Ok since everyone said I didnt give enough info before here is the same question with the info added in. I own 5 horses that are in a pasture at a boarding facility, the pasture has no gr and I have tried planting gr seed but it wont grow. They each have their own stalls and I feed all of my horses on my own so I know they are getting what I give them. There is one more horse in my pasture who is my friends horse so in total there are 6 horses in the pasture because we get our own pasture, stalls, and tack room. I put out a round bale somewhere between 600-900# in a round bale feeder so none of the hay was wastes and between these 6 horses on it for 23 hours a day (1 hour for feeding in the morning and the night 30 mins at a time) They ate it in 2-3 days... I cannot lock them in their stalls at night because they destroy the stalls if they have nothing to do.. so I decided to switch to square bales so I could monitor what they eat.