Baytril is bitter, so it will work better if you give it orally. The injectable is nice because it can be given by injection or orally. By injection is how I give it.
Selling eggs... Sigh, that's a tuff call. I eat them, but not sure I would use Baytril if I was selling eggs. How about this... Maybe buy some Baytril and pick one bird to treat. If it gets better, then you can look for a non-banned drug that's more effective than the oxytetracyline you're using. Problem with the oxytetracyline is that many bacteria are resistant to it. If the one you treated with Baytril doesn't improve, there's a pretty good chance that you're dealing with a virus.
Well i currently have just the one hen that has it the worst, so I could feasibly treat her with the baytril. She seems to be doing a lot better now though, as far as how she appears to feel. Everytime I go check on her she is now standing up trying to roost on the side of her box instead of laying down inside of it. She still sounds like crap, but acts like she feels better. I hate to spend any more money than I already have on all of this stuff, especially since I dont know what we have or how the outcome will be. We usually have extra spending money but this has completely depleted any and all extra money we have. As much as I REALLY hate to say it, I am half tempted to cull her if she does not improve much faster over the next week, but its probably too late for that since everyone else has already caught it. So far the rest still just have runny noses and are lethargic, no sneezing and no rattley sounding chests like my one hen. but no one is laying at all, they have gone on strike! I JUST DONT KNOW WHAT TO DO *cries like a baby*