Exactly what Greg said. It's called trash breaking. You want your dog to associate deer scent with nothing but bad, especially if he's killing fawns.
I do it with snakes, possums, coons, deer, and any thing else that might come up. Like Greg said, the easiest way is with an ecollar because you can correct as soon as the smell hits the nose. By correct I mean give the dog a bad experience, one that the dog will not soon forget or soon repeat.