Weaning in mice refers to the developmental stage where young pups transition from relying solely on their mother’s milk to consuming solid food and becoming independent. This period represents a significant milestone in their growth and overall well-being. It is a natural process that prepares them for adult life, where they will forage for food and water independently. The successful completion of weaning is important for their continued development.
When to Wean
Mouse pups are ready for weaning between 21 and 28 days of age, with day 0 being the day of birth. Some sources suggest that most rodents can be satisfactorily weaned as early as 17-18 days of age. However, individual readiness should guide the exact timing.
Signs that pups are prepared for this transition include actively exploring their environment, nibbling on solid food, and drinking water from a sipper tube. Their eyes should be fully open, and they should have developed adult fur rather than the sparser coat of neonates. Pups that are ready to wean might also exhibit a “popcorning” behavior when the cage lid is opened.
The Weaning Process
Introducing solid food to mouse pups should be a gradual process. Approximately one week before the intended weaning date, you can begin placing a few softened lab block pellets or moistened chow on the cage floor, making it easily accessible to the pups alongside their mother’s milk.
Proper water access for newly weaned pups is important. Even if the cage has an automatic watering system, a water bottle should also be provided on the cage floor. Many young mice may not yet know how to use the lixit valve of an automatic system, so “charging” the lixit by toggling it with a gloved finger to ensure a drop of water is hanging can encourage them to learn. Gel packs containing both food and water can also be placed on the cage floor to provide hydration and dietary support during the initial transition.
The separation of pups from the mother involves moving the pups to a new, clean enclosure. If the breeding setup involves continuous housing of males and females, or if a second litter is born, the first litter must be weaned by 21 days of age to prevent overcrowding and interference with the new neonates. Moving the pups calmly helps minimize stress for both the mother and the young mice.
Provide a safe, clean, and warm environment for the newly weaned pups. This includes adequate bedding material, such as pre-shredded cotton nestlets, to allow them to build nests and regulate their body temperature. Maintaining a stable temperature, ideally between 20-24°C (68-75°F).
Post-Weaning Care and Monitoring
Following weaning, consistent monitoring of the pups’ health is important. Daily checks should be conducted to observe food and water intake, assess weight gain, and identify any signs of stress or illness. Pups that are small for their age, less than 10-12 grams at 21 days, may require prolonged monitoring and additional support like soft diets or gel supplements placed on the cage floor.
Housing weaned pups in same-sex groups is recommended to promote social development and prevent fighting, especially as males mature. Littermates should be kept together when possible to maintain social stability. Avoid introducing new, non-littermate adult males into established groups after 6-8 weeks of age due to potential aggression.
Any persistent signs of dehydration or weakness should prompt consultation with veterinary staff.