Akrnaf2, I must respectfully disagree.
Treating birds with "preventative" antibiotics creates resistance, and not every antibiotic treats every infection, either.
I never recommend throwing medication at a bird unless you KNOW what you are treating for.
In the case of FP, it's best to keep a sharp eye out for any flock member that appears to be declining in health. THEN you can begin treatment... but, again, ONLY if you KNOW what you are treating for.
If you see anyone become lethargic, quit eating or drinking, go pale in the comb, start wheezing, or have discharge coming from their eyes and/or nostrils, THEN take action. But giving antibiotics to a chicken that doesn't need it will do more harm than good, in my opinion.
MrsB