If you decide to raise your own feeder mice there are a few important details that make the difference between success and failure:

Mice thrive between 60 and 80 degrees F. If you keep them in an unheated garage or shed, with temperature extremes above and below these points some may survive, but reproduction will be slowed or end as the temperatures reach extremes. If you've ever had a mouse in your home, you know that they eat most anything. True also with feeder mice. Good production is tied to proper nutrition. Feed your mice mouse food. 2018 Teklad Global 18% Protein Rodent Diet is a good source for mouse nutrition. Keep mice clean and dry. Dirty cages mean damp mice, susceptible to illness. Juveniles die quickly if they don't stay warm, not easy to do if you have no hair and the bedding is wet!