mice are easy to breed and I never had any problems with large litters being nursed, maybe one or two die offs at the most. THe only problem I had with pinkies dying off is when there are older babies around (these just push the pinkies out of the way of food, eventually they grow weak and die).
I find it best to breed 2-4 females per male mouse, housing all together all the time. If you are aiming just for pinkies, I suggest culling about half of each litter of pinkies and let the mothers raise them for awhile. Otherwise, when you want bigger babies, the mothers won't know how to raise them after a few days and may wind up abandoning them.
if you have adult snakes, then this won't be a problem, just raise the babies up in a separate tank (once weaned at 4-5 weeks old) till they are the size you need then freeze them(prekill first of course).
However, if you are only looking to feed baby corn snakes pinkies, it would be cheaper to order 100 pinkies or more from a online supplier. By the time you buy a couple cages (rubbermaid bins, whatever) water bottles, rodent chow, young adult mice and bedding, you probably would have paid for the mail order pinkies.
breeding your own mice works best when you have a few different snakes that need different size food, so you can freeze some, feed immediately others and grow up more for later. I also don't recommend breeding mice if you live in a one bedroom apartment or don't have a place you can isolate the mice in, so the smell of the male urine doesn't stink up the entire house. Constant cage cleaning will only get rid of the smell for a short period of time. Male mice just have a strong musk scent to their urine.
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PHLdyPayne