Quote Originally Posted by wolfman38
But stay away from mice, they don't have the noutrishinal(sp) value as the rats do.
That's a common misconception... adult mice actually have more calcium, not nearly as much fat, and only slightly less protein than adult rats. Of course, the size of the prey is a big issue, but 2 adult mice a week is perfectly adequate, especially considering this is a male we're talking about. Growing to a large size isn't necessary (for breeding purposes anyway). Actually, reducing caloric intake has proven to result in increased longevity in every animal for which this has been tested. So, I would not be worrying too much about him eating only 2 mice a week, and I'm very surprised to hear that he is "underweight" if he has been eating those mice steadily (unless those are some tiny juveniles). With that said, it is definitely preferable to have him on rats, as (obviously), they are a more appropriate size for a 3.5 foot ball python. I would just gradually increase the size of the rats you feed him... he's obviously unaccustomed to anything as big as a medium rat, especially having just come from mice. But, if he'll take rats already, it should be simple enough to up the size on him so I wouldn't worry one bit.