I have a flock of about 35 birds, ranging in ages 3 weeks to a year and a half. On Sept 23, I was at a poultry show showing my birds (it was a cold and windy day at the fall fair) and we bought a blue cochin hen. We brought her and my birds home, and set them up in the basement for quarantine time. My mother got impatient (it was our first time quarantining birds) and lobbed them in with everyone else after just 3 days.
My birds were fine, but the cochin started to sneeze. I researched sneezing in chickens, and tried to listen for gurgly or wheezing breathes - i could hear none, so i left her, and a couple of weeks later, she was wheezing BAD. So she came back inside and was immediately given some antibiotic powder dissolved in water. I believe we are using Tetracycline. About 4 days later, two of my nice cockerels developed gurgly breathing. They joined her and the date marked on the calendar.
Because my chickens free range, and can drink water from any waterer in the barn, an the cochin was wandering around sick for so long, should I give the antibiotics to the whole flock to make sure they don't develop this? I know I would lose 2 weeks of eggs but that is better than losing 2 good hens. I also know that it may mean they can develop a disabled immune system. I have 2 young chicks, 3 and 5 weeks, with a broody - will the antibiotics do something horrible that could affect them and other birds that come in contact with my birds (ie creating non-symptomatic carriers, or weakening immune systems)?
I'm stressed, my birds are stressed, and I'm wondering if it might be good to use antibiotics on the whole flock to make it easier and have faster recovery?
Thank you for any and all replies.