If I think my birds have a disease, and I decide to start vaccinating my new mail-order eggs once they hatch......how many of the different respiratory vaccinations can a chick handle and how often? Also, what would be the best way to vaccinate and for which diseases? My current older birds act like they have CRD. Also, I train, race, and raise Homing Pigeons, which fly around and come into contact with numberous wild birds with foreign diseases.....so would it be best for my to vaccinate my new chicks for everything respiratory? I sell my eggs through mail-order.....so I cannot sell now due to this new bird virus I have. So I have to replace my older stock with new stock birds.....so what would be the best vaccinations and why?