I have read so much about cocci lately, I don't know where I read it, but chickens that free-range a lot are less likely to suffer from a cocci overload b/c they have built up an immunity. But mine are little & spend a good deal of time in a brooder. After yesterday's hawk debacle, no one was allowed to free-range today. I FINALLY found the Corid at Roche's & dosed every chicken I got. Fingers crossed!