If it gets to the point that you are worried and/or he's losing weight I would consider offering him a live rat of equal/slightly smaller size. I have a pastel that will not touch f/t no matter what I try but is a voracious feeder on live mice. she also will not eat a Norway no matter what I try. Only mice and asfs. Some snakes just are picky. Try live and see if anything changes. Just my two cents. Good luck with it!