It would be my guess that stress could be the reason he is not accepting food. Try to reduce his stress for a week or two before trying to feed him again. Don't handle him, keep him in a dark cage with a nice, secure hiding box. Make sure his temps remain between 84 and 90 (night and day). After he has been left alone for a while offer him the rat again. If it is frozen-thawed make sure it is warm to the touch or at least that it's head is warm. Burmese use their heat-sensing gear to determine what they confront. If a food item does not register as a warm, living animal the burmese will sometimes not consider it as an edible thing. Make sure it's warm so it registers as a "living thing" to him.
Next, when offering it to him, read his body language. If he turns and hisses and tries to get away from it, instead of facing it and showing interest with quick tongue flicks then he isn't interested in eating and it's best to leave him alone and try another day. If he does face it and show obvious interest then cause it to bump into his neck. He should turn into it and grab it as "neck bumping" tends to stimulate a feeding response in most pythons.
If all this fails try leaving a live pre-wean rat or a large fuzzy in with him overnight. Make sure it is not old enough to become defensive and attack your snake.
Let us know how it is going from time to time.
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David Beauchemin
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