What age to Start a Catch Dog?

My children have taught him to walked with a loose leash since he was 2 months old. He is very level headed and observant. I think he is going to be the walk or trot in and catch kind of dog (which I thoroughly enjoy). I can let him catch a wild shoat in the pen and then bring him back to my yard where we have a domestic pig (the same size) running loose, leave them both loose, and he will not catch it. I have made him sit and watch while other dogs were baying or catching...for the most part he was sitting but whined the whole time. What advice do you give to correct that? Would you use a shock collar in any of these training situations?