Won't Mate?

[MitsuMike]

Well just weighed in a female who looks a bit bigger than normal and she was 340ish grams. I think she is prego. w00t

Well she was not prego......=( They are just rediculously HUGE!!! Im talking like 350-400 grams each.
Is it possible that the Male rat is sterile?? Should I buy another male and see what happens?