Yes, the younger burms seem to absorb more of the food when they are younger, but also, these seem like small meals, even for a 3 foot baby. Have you measured this guy at 3 feet, or are you guessing? Because I have seen HUGE discrepancies when people guess in both ends of the size spectrum. I have had people tell me their burmese was 8 inches when in fact it was closer to 24 and then I have had people say that their snake was about 2 feet and it was closer to 4 feet. It's often hard to judge. But if your little guy is in fect 3 feet he/she can easily take down medium to medium large rats. I start off my 2 ft hatchlings on small rats or jumbo mice. These guys are designed to take down large prey items. Once you are feeding him/her more I'm sure you will see a nice little cycle of eating and defecation with relative regularity.
By the way,.. I am Damon 
>>Just my opinion, but if you do not eat enough, you will not "go to the bathroom" either. I am not saying that you are starving you burm, but the food that he/she, sorry I could not remember, is being absorbed by the body and used for growth. That may be why there is no "poop". Personally, when my burm was about that length, he was eating small rats and giving me regular defications(sp?). I just believe that most, if not all, of the prey item being offered is being used by the body for growth and that may be why there is no defication(sp?). Maybe someone else here like Damon or Rob can help you better, but this is my personal opinion.
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>>Jason
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Believe in yourself and your abilities and you can accomplish anything.