she wants to herd them (she's a cattle dog) and wants to nip them to turn them and her nipping is dangerous. I have taken her out on a short lead with me and she tries her darndest to get at them. I correct her but I can tell her herding desire is still too high. she doesnt pay them any attention when they're in the pen. it's like she knows they are where they should be but if they are out and about in the yard it drives her crazy!