i have seen a few folk try an reward the retreive wiith a tit bit mate, an the 1 thing i have noticed with all the dogs is they spat bunny out on approach in anticipation for the reward.....
must admit tho, neither i or the folks i seen try this technique are experts
i used it not long ago and only gave it when it handed the rabbit over make shore you have the rabbit and wait a few seconds after you get it before you give it with prays do not show it or offer it till he his back