We are moving in April to 5 acres with about a dozen or so mature oak tress. They are all dormant so I couldn't really determine what kind they are just yet. But the ground is naturally covered in leaves and acorns from the trees. Will it be harmful if my goats eat these? I think I read somewhere that fallen leaves, acorns, and even branches or bark were fine. But green/live leaves were a no go for some reason?