I have two horses. They play horse games by biting each other. They keep biting each other in the same area on their neck and mane. One horse has a large circle of her mane missing. The hair that is pulled out is smooth with all of the hair in this area gone. Is this normal? Usually, if you pull hair out you would have a few hairs left in the area and not smooth. Does she have ringworm? Does anyone know what I am talking about?