Hi, I'm a new chicken mommy trying to learn all I can. I've read about deworming chickens when there's an infestation, but do you do it as a sort of "preventive maintenance"? ...If there's anyone out there with horses, we worm our horses every 2 months whether we see worms or not -- Is that necessary for chickens too? If so, at what age do you start and what do you use? Thanks!