Chubby does not mean healthy, you seems to be feeding high fat content when they really need high protein content.

Mice as well as rats need quality food designed for the purposes (generally speaking most food found in pet stores are not quality and definitely not designed for a breeder/feeder colony)

I would highly recommend you to switch to lab block designed for feeder colony, you can also mix you lab block with some dog food (16% to 18% protein content with no red dye)

The major factors in cannibalism are

  • Low quality food
  • No water available
  • Stress
  • Over-crowded enclosure


Mice colony are often harder to get started compare to rats however once you get everything right you should be able to have a colony that produces well with avery limited amount of cannibalism.

I would feed them all of and start from scrath again.