Are you attempting to feed in his cage? Or in a feed box? Mine gave me trouble with his first thawed, too. I read that they may be a little cooler with it if you leave them in the cage. Then bring in the thawed with some tongs or hemostats and give it a dangle in front of the hide. Worked for me, was a little like fishing. Now I feed in a feed box (just a big cardboard box with the flaps taped staight up for more security) with astro turf like in his tank. He seems to feel safe there and will eat thawed in the box.
If he still wont eat thawed, then buy live and stun/kill it before feeding. Anything to avoid a nasty bite!
If that doesn't do it, wrap the rats muzzle in some biodegradable surgical thread......................LOL
now I'm getting silly...... :roll: