One thing to remember when trading toys for treats while playing fetch with your hound, give him a moment to swallow. If you throw the toy immediately, a hasty hound will sometimes inhale the treat and the game is interupted with hacking up a treat.
Riley is the worst. Treats just sit on her tongue and she often spits them out unknowingly. At the indoor training building, I walk around and collect the dropped treats and reuse them.