I know you don't see all worms, but you may have worms too, your dog, your cats, we don't worm them all the time. I AM NOT against worming, so please don't think that, but I feel those wormers are quite strong and can make a weaker hen very sick, just like any animal, these are strong chemicals. Most of us got our own chickens so that our food would be more natural and chemical free. I live in NH and work in VT, the farmers I talk too don't worm there hens unless they are showing signs that they may have worms( then I would worm too). I read here of people worming once a year,not a bad thing to do, but what if they get worms in them the next day form eating somthing, those worms will be there for the rest of the year. I am not saying I am right believe me, but like alot of folks here I am not sure, so many different opinions. I personally believe that if they are healthy, live in a clean environment with fresh food and clean water and allowed to free range then my hens should be ok until I see one of them looking thin, weak, or see worms in there poop. I know mother nature knows more than us humans, hence the free range comment, I am sure some of the things they eat in nature must be helpful with natural worming, wild chickens don't get wormers from the store, just a thought! don't hate me, but wormers are insecticides-toxic stuff