I'm relativly new to herding, but my dog isn't. He's about two and was considered "fully trained" when he was a year old. Currenty he is worked mostly on goats, due to my line of work, but I've noticed this issue with both goats and sheep. Often with goats one will be far away from the herd and I'll send John out to get them back in, when they are particularly stuborn he will just chase after them ignoring down or any other command I give him. This isn't an issue when we're working in a closed feild but out in the open he'll chase them into kingdom come. How can I get him to disengage from the