I have a couple of chickens that are breathing with their mouth open and you can hear mucus in their throats. Coughing and sneezing, but not a lot of either. This is their 3rd day for Tylan injections, and one still has the throat rattle, so I thought I would continue the injections for another 2 days. No significant nasal discharge, no bloody mucus, nada eccept what I have described. Oh, and no diarrhea. Is this infectious bronchitis?