I used to breed rats for about 5 months, the work load was just too much for me and i only had 6 snakes. I am one who has no issue feeding off rats or mice or anything for that matter. I did have some rats that were strictly pets, NEVER TO BE FED OFF. Those i always played with and socialized with, but others were strictly feeders, also some of them were pretty mean too and had bitten me numerous times, so i really didn't care.

I can understand you not wanting to harm the rats, but you gotta do what you gotta do. I remember i sold off about 7 or 8 of my adult rats to a gentleman for his Retics and i didn't realize it until i was taking them out of the tub that half or more of the girls were pregnant with huge babies. I was shocked and felt bad for the babies, but it's only going to be more nutrition for the snakes that eat them and i could not take care of the 20 or 30 babies that were coming out.

In your situation, i would feed off the female before you have babies, but if she is small and this is her first litter, she might only have 2 or 3 and heck she might even eat them, which is fairly common. Then again she might be like one of my females who had 13 her first litter. Either way you would have to take care of the female more since she will eat more and drink almost 3 times as much and you will have to feed off the babies ASAP before they get old enough and start impregnating each other, then you have a real mess on your hands.