I have a bc dog that's about 9 months old. I don't work him but he is out of working parents. I trained him the basics, how to walk on and off leash, recall and that's all. He is, or was, a good dog as far as obedience goes. Anyway I live near a lot of commonage and there are often sheep and cattle walking about on the loose, in my driveway sometimes, sometimes livestock gets pretty close to the house. Until recently I could call my dog to heel when we walked by loose sheep. I spent a lot of time on recall when he was a pup. I've actually called him off sheep that we walked by that started running serveral times. Once when another loose collie pup was chasing them like mad I called him once and he came back. After that I thought his recall was rock solid. But something clicked in him recently and his drive to chase has kicked in big time took me by surprise. He's chased sheep about three times, now without coming back right away, since that happened I've been working with him and it's helping. I've taken him up to the bog and had him up close with sheep in a closed area to get him accustomed. The first time I did that I noticed that he was a bit afraid of the sheep up close. He's afraid of them until they run then he goes mental wanting to chase. Don't really want to use a shock collar on him but I will. The farmers, my neighbours, will land at my door with guns if he chases their sheep especially during lambing season. He's only doing what's natural for him so it's not going to be easy I realize.