Remember what I said about withholding feed for 24 hours prior to worming them? It would be best to keep them in their run/pen and provide water only. If you let them free range they will eat grass, bugs etc...it would be defeating the purpose of worming because it would also be feeding the worms nutrients keeping them strong. Withholding anything to be eaten weakens worms. Chickens can handle not eating anything for 24-48 hours.