Hi chicken lovers. I inherited 2 older hens 2 years ago, really as pets. This spring my husband & I bought 9 chicks: 2 Rhode Island Reds, 2,Americanas, & 5 Polish (no roosters). We live in the country & the hens free range all day & return to the coop in the evening. They constantly have worms, & DE hasn't helped at all. Since they are exposed to worms daily while free ranging, is it really necessary to worm them? If so, how often?