Had a real sick chicken with respitory problems. At the tractor supply store they suggested Duramycin 72-200 since they were out of the chicken kind, and it was a holiday weekend when all other reliable sources were closed. I was feeling desperate since I'd had a bad 2 weeks with a lost chicken (problably fox), a chicken that died from what looked like crop impact, and finding a 6 foot snake wrapped around my front door handle (which had been eating all my eggs). In desperation and fear of anymore mishaps I took it home. My friend helped administer a tiny amount to all so there would be no more illness and we also added de-worming to thier water, which turned out effective. They had round worm. So from the info I have found 28 day egg withdrawal to be the most common answer. Is giving them thier eggs back bad because they are taking in smaller doses of the med making it less effective if they ever need it again ( hopefully not). Also that extends withdrawal period? So many questions. I hope I did the right thing, though probably it wasn't the best.