Why pet only? Given up trying to train the dog how to chase? How is your training going? Have you been taking the dog to a professional muscleman to get it checked over for injuries?
I would have suggested that for a first time trainer, it's best to take in an older dog instead of a young pup/just broken in dog, as it's so easy to ruin them for racing by playing with them too much and making them nervous/or silly. With an older dog, it would already have been trained properly and developed its own habits.

A good dog makes the trainer. ;-)