I've never given them anything at all, but having done a lot of research once Olivia got sick, I'm now wondering if I should. And if so, what? I have 3 chickens, w/ no intention of getting more. Olivia had a completely clean fecal at the avian vet's. Do I need to do anything as far as preventative worming? I prefer not to give them toxic substances without good reasons . . . . Would it be better to just take a fecal sample in every few months?