The reason the antibiotics will not be available to prevent their overuse when not necessary, which leads to antibiotic resistance in all of us. Antibiotics do not treat viruses or fungal diseases. That is why is is most important to try and get one or two birds tested--to know what disease is present. Someone just posted necropsy results of their chicken who had infectious bronchitis (a virus,) mycoplasma (similar to bacteria,) and a mild strain of Newcastles Disease (another virus.) It can start with a mild virus, then be complicated by other diseases. E.coli is one which is opportunistic, and can one a common bacteria in air sacculitis, a very deady complication of any respiratory disease. This link lists the common respiratory and other poultry diseases and symptoms: http://edis.ifas.ufl.edu/ps044
