Mine are grazing all the time too...I don't let them graze much in other people's yards because the grass might be sprayed. They can eat as much as they like out of my backyard. They don't pull it up at the roots either, it grows back really quickly. I have noticed that the grazing has lessened a bit since I've been giving them more fruit...don't know if there's a connection or not.
ETA: Moto, I used to grow wheatgrass for the dogs. They wouldn't eat it :roll: