A friends is moving to an old commercial poultry farm. The chickens have been gone for 2-3 years. There are huge buildings that the chickens were raised in on the ground, not cages. I do not know the reason for it shutting down. The ground in the buildings are dirt with 8-12 inches of dried droppings from the chickens. I don't know how commercial poultry farms raise the chickens, so I have no idea if it is safe to put new chickens in there. The space will be primarily for horses but also some chickens. Is there a possibility of anything that can harm the chickens or horses?