What do feeder mice eat?

The same food as pet mice--it's just another way of categorizing them. Grains and seeds are good, and you can buy food blocks made for mice and rats. If you need something quick, though, mice will eat practically anything--crackers, cereal, bread crusts, oatmeal, sunflower seeds, pumpkin seeds, and raw veggies. Don't feed them lettuce, though, as it has too much water and not enough nutrition. And don't give them sugary food--they'll eat that and not eat what's better for them.