The best basic diet for mice is a pelleted or block-style feed made specifically for rodents. Foods labeled for mice or hamsters are preferable, with a content of 16 percent protein, 18 percent fiber, and 4 or less percent fat. Mice should have a constant supply of this food at all times in their cage.
Fresh foods in the form of green vegetables are also important to a mouse’s daily diet. A tablespoon of greens is enough for most mice. Favorite greens include broccoli, arugula, collards, turnip greens and cilantro.
Mice also benefit from having grass hay, such as orchard or timothy hay, in their cage at all times. This gives them something to nibble on while providing fiber in their diet.
Whole grains such as millet, barley and oats can be given to your mouse in small quantities, no more than a 1/2 teaspoonful per day.
Other foods, such as table scraps and fruit, should only be given occasionally as a treat, maybe a few times per week in small amounts. Never give your mouse food containing processed sugar, chocolate or caffeine, or anything spicy. Corn and wheat have also been known to cause digestive problems for mice, so avoid these foods.
You can give raw sunflower seeds sparingly to your mouse as a treat. If your small pet starts to put on weight, cut back on the seeds because these are high in fat.