How much should a mouse weigh? - briefly
A typical laboratory mouse weighs about «20–30 g», while a wild adult averages «10–25 g». Strain, sex and age determine the precise mass.
How much should a mouse weigh? - in detail
The appropriate mass of a laboratory mouse depends on strain, age, sex, and purpose of use. Typical adult weights are:
- Mus musculus (common house mouse): 20 – 30 g for females, 25 – 35 g for males.
- C57BL/6 strain: 20 – 25 g (female), 22 – 30 g (male).
- BALB/c strain: 18 – 22 g (female), 20 – 28 g (male).
- Outbred CD‑1: 30 – 45 g (female), 35 – 55 g (male).
Weight ranges serve as benchmarks for health monitoring. Deviations of more than 10 % from the expected range often indicate underlying issues such as disease, malnutrition, or stress. Regular weighing schedules—weekly for juveniles, bi‑weekly for adults—enable early detection of problems.
Key factors influencing body mass:
- Genetic background: Inbred strains exhibit narrower weight distributions than outbred stocks.
- Developmental stage: Neonates weigh 1 – 2 g; weaning occurs at 20 – 25 g.
- Environmental conditions: Ambient temperature, cage enrichment, and diet composition affect growth rates.
- Sex: Males consistently outweigh females within the same strain and age group.
Guidelines for maintaining optimal weight:
- Provide a nutritionally balanced diet formulated for the specific strain.
- Keep housing temperature between 20 °C and 26 °C to prevent thermoregulatory stress.
- Monitor water intake and ensure continuous access to clean water.
- Conduct health assessments, including physical examination and clinical pathology, when weight falls outside the expected range.
In research contexts, precise weight control enhances reproducibility. Dosing calculations for pharmacological studies rely on accurate mass measurements; errors of even a few grams can alter drug exposure significantly. Consequently, standard operating procedures mandate calibrated scales with a resolution of 0.01 g and documentation of each animal’s weight at defined intervals.
Overall, the target mass for a mouse is defined by its genetic profile, age, and experimental requirements. Maintaining weights within the established ranges supports animal welfare, data integrity, and regulatory compliance.