You're lucky that the oxytetracyline works for you, but it will not treat *many* on the bacteria that can be associated with upper respiratory diseases. Oxytetracyline is very unlikely to treat E. coli or pseudomonas aeruginosa. For either of those you would need something much stronger.Your right...Oxy Tetra-a will not cure my birds...During an out break it does help with symptoms being the disease if left untreated can become so bad that they die..A Bio-security Vet for Poultry and Swine recommended I cull my entire flock of 11 pullets and wait six weeks and start over...He understood my hesitation to do so and told me to give them OXY TETRA-A...Who knows if they will make it over winter?
I will see how things go...I hope the OP has great luck...
-Kathy