This sounds cruel.........but could do the trick as long as your dog doesn't love water! Get yourself a cheap water pistol and when you see your dog bothering your rabbits give him a quick squirt with the water pistol! Make sure you do it sneakily and from a distance so he doesnt know where it came from, otherwise he will associate it with you. He should soon learn that when he pesters the rabbits he gets a squirt! Providing he doesnt love water, it should discourage him! Just an idea......has been known to work in the past! Good luck :-)