When mice can be taken away from their mother...

[Batdad]

New to feeder raising, the first litter, two left, have their eyes open and are wandering around container. Can they be separated into a different container to be grown into more breeders or should I wait? When do they start the solid food thing? They are three weeks old. More litters coming up behind them and I want to keep some of these first litters as breeders because the original mice were all pregnant when I bought them so these will have different blood lines than the later generations to come.
Also they are sexually mature at what six weeks? Going to have to watch that

Thanks for any help
Bruce