Winglet I have my suspicions that the medication may actually act to supress there immune response somehow, as in it does not let them build up the natural immunity that they otherwise would without the medications. I changed my feed this year to a turkey grower mash that I buy by the tonne from my local feed mill. I feed everything from day olds to breeders with it. For this reason I have had to get it without the medication in it because you can't give it to layers. I have not have one case of cocci this year, every other year I have not missed out in some way or another. Does not seem to make sense on the surface that you would have less trouble without the meds that with does it, when they are suppose to aid in their ability to handle it! It's chicken food for thought!