Report training advice for my rescue BC in General Border Collie Discussion Posted July 18, 2019 Get a new trainer. If part of your dogs aggression problem is fear the shock collar will only make it worse. Of course having never seen your dog in action I have no idea what's driving his behaviour, I just know that I would only use a shock collar as a last resort and after training many, many dogs, I have never come to that point yet. There is a really good way of teaching a dog not to be dog aggressive. It's a bit involved and uses a few volunteers and their dogs but it's highly effective. You put the most submissive dog of the opposite sex in a down on the other side of a chain link fence (their person should ensure the dog holds the down). Then you start to walk the aggressive dog toward it. As long as the dog is not behaving in an aggressive manor it is allowed to continue to approach. As soon as any negative behaviour shows, give a leash correction and walk the other way. As soon as you have control again turn and go back toward the other dog in the down. Praise them quietly as long as they are calm and well behaved. When your dog can approach without behaving badly you allow the submissive dog to stand and repeat the whole process. Then you move on to more confident dogs and finally dogs of the same sex (begin again with the most submissive in a down). It takes some planning but I've never known a dog that it didn't work with.