Back to back breeding is not the best the female being pregnant while nursing a litter will take it's toll on the female not to mention you will produce smaller litters and babies may be smaller as well.

I rotate female and remove them when pregnant to set them up in individual birthing tub until the babies are 5 to 7 days old, this prevent females from fighting over babies leading to serious injuries and losses.

Once the babies are 7 days old I do communal nursing at that stage the babies are less likely to be injured.

Now back when I rotated males I would leave the males 2 weeks with the females before moving them to the next tub.
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My advice do not leave the male in and definitely do not remove the male to put him back later on or you will even more likely to get the offsprings killed.

Put the male back in when the rats are weaned at 3 weeks and in their own tubs.