All my chickens appear to be fine, but a friend experienced with chickens came by my coop, held one of my hens and said that she has a respiratory disease. She said she could tell this because she could feel her breastbone and that you should not be able to feel the breastbone of a chicken. She advised that all my chickens need to be treated with antibiotics. I am not keen on giving my chickens antibiotics if it isn't absolutely necessary. Has anyone heard of anything like this? What disease is it?