How do you think hobby breeders breed mice? Handling does not stress a mouse that is tame. With small time mouse breeders, handling is your best bet, because you won't have to worry about stressing the females by picking babies out. I've had plenty of mice that have been handled throughout the pregnancy and raising of the litter, along with daily handling of each litter from day one, all without any problems. I only hear of major cannibalism stories in feeder breeders, it's not as common in fancy breeders because these folks have tame mice.