It depends on how he reacts to things. You can "play" with them yourself, and don't let him have the toy immediately, make him want it. Or, just leave them laying in his bed and let him start gnawing when he's bored. If he chases a regular Frisbee, try throwing the Orbee disc instead.
I'm not sure why there's a hole in the middle. By the way, and you might want to try this in a wading pool or bathtub first, I think I remember something on the tag of mine saying the bone floats.