A baby mouse, often called a pup or pinky, has a diet that changes completely and rapidly over its first few weeks of life. The pup’s nutritional requirements are dictated by its age, moving from liquid sustenance to a solid, varied adult diet quickly. Understanding these transitions is necessary for anyone caring for young mice.
The Initial Diet: Mother’s Milk
For the first 10 to 14 days following birth, the pup’s sole source of nutrition is its mother’s milk. This milk is rich in fat, which is important for the rapid growth characteristic of young mice. The high concentration of nutrients supports the extraordinary rate of development during this early period of life.
Maternal milk also plays a significant role in establishing the pup’s foundational health and immunity. It contains complex components, such as the complement system, which help shape the infant’s gut microbiota. This process provides protection by targeting and eliminating certain types of gut bacteria, making the young mouse less susceptible to infectious threats. Pups are completely reliant on the mother for both nourishment and the development of a protective internal environment.
The Weaning Process and Transition Foods
The transition from an exclusive milk diet to solid foods, known as weaning, is a gradual process beginning around two to three weeks postnatal. This period is marked by a decline in nursing and an increase in the pup’s interest in the mother’s food. The weaning phase often lasts from day 18 to day 28 after birth.
Pups first sample soft, easily digestible foods that mimic milk texture but contain more complex nutrients. This might include moistened adult food pellets, baby cereal, or soft grains the mother brings to the nest. Introducing small pieces of rodent chow before weaning helps the pups’ digestive systems adjust. This gradual introduction is necessary for developing gut enzyme activity, preparing the digestive tract for the adult diet.
Diet After Weaning: Adult Foods
By about four to six weeks of age, the mouse is fully weaned and transitions to an adult diet. For domestic pet mice, the foundation should be a high-quality, nutritionally balanced commercial rodent lab block or pellet. These manufactured blocks provide the correct ratio of protein, carbohydrates, vitamins, and minerals that a mouse requires. A diet consisting solely of seeds and grains is insufficient, often leading to nutritional deficiencies and obesity.
The protein requirement for a growing mouse ranges between 14% and 20% of the diet, slightly higher for breeding females. Protein acts as a source of amino acids and supports the body’s structural and metabolic processes. Mice also require complex carbohydrates and fat, including unsaturated fatty acids like linoleic acid. Wild mice consume a highly varied omnivorous diet of seeds, roots, fruits, grains, and insects, which naturally provides necessary nutrients.
Specialized Care for Orphaned Pups
When human intervention is necessary for found or abandoned pups, the diet requires careful formulation and delivery. Cow’s milk is not appropriate due to its incorrect balance of fats and proteins, so a specialized milk replacement formula must be used. Acceptable options include powdered Kitten Milk Replacer (KMR), puppy milk replacers like Esbilac, or human soy-based infant formula.
The formula should be prepared fresh daily and warmed to skin temperature before feeding, as cold formula can cause fermentation in the pup’s stomach. For delivery, a small 1-milliliter syringe, an eyedropper, or a fine-tipped paintbrush is used. The pup must suckle the fluid rather than having it forcefully squirted, which prevents aspiration and subsequent pneumonia.
A crucial step for young pups is stimulating elimination, as they cannot urinate or defecate without the mother’s assistance. After each feeding, a soft cloth or cotton swab dipped in warm water must be gently rubbed over the pup’s genital and anal region. Orphaned pups require feeding every two to three hours for the first few weeks, and formula changes should be avoided due to the mouse’s sensitivity. Rearing abandoned wild pups is extremely challenging and often requires the expertise of a wildlife rehabilitator.