Females bred right after birth physically stop impregnation of the embryo for up to a week, then they do not go back into heat until after her litter is weaned. This is due to the fact that once the pups are weaned, the females teats are unsuitable for pinks to use. This week delay gives her teats time to shrink and recoup.
Communal nursing is easiest between litter sisters rather than unrelated females, but there is a very fine line between continuous success, since some studies show that communal nursing has a higher mortality rate than single mother nursing.
I always wonder truthfully the condition of the females and the weights of their pups on weaning. I can't believe that back to back breeding isn't hard on the female, and that the females and pups are reaching the weights of females that have litters every 8 or 12 weeks instead of every 4.
Anyways, hot topic. Do you actually wean 240 rats per rack per month?
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