What exactly does breed for resistance mean? Does it mean to allow your flock to be exposed to illness? Or does it mean to not use any vaccinations, and allow them to be carriers? What diseases are there that should be bred for resistance? All diseases, or just some? Sorry, I just don't get it. I don't want a sick flock, but I don't want to have to give meds and vaccinations all the time either. Please explain all this to me. Thanks.