I have smacked 2 of my dogs for chasing kangaroos. They have good recalls, but when I first moved on the farm the only thing that made them think twice was a smack. I think it had shock value because it is not something I usually do. Now with kangaroos I just have to used a strong recall voice and they know by the tone of my voice that I will smack them if they dont obey.
They also know that this probably the only situation I will smack them for. I didnt call them to me before I smacked so they didnt associate coming with a smack, I caught the 2 offenders when they bought the roo down and I was so angry as I was dodging kicks from the roo. Everyone including the roo escaped without injury, but it could have killed with a kick. I just wont have it. The other dogs knew I was angry and kept well clear of the whole debacle, like butter wouldnt melt.