How long is it for you between when you introduce a female to a male, let them have their babies, then re-introduce them again. I like to try and give my females plenty of time, just wondering if I give them too much or not enough, but here is what I do. I put .3 rats with one male rat (I just did this yesterday). In two weeks I move the females down one tub and put .3 more in with the male. I have a 4 tub system, so I do this two more times before the first group of females get put back in with the males. So from the day I start pairing to the day that first group of females get back with the male is 8 weeks. How often do your breeder females see a male?