How quickly do mice grow? - briefly
Laboratory mice become sexually mature around 5–6 weeks of age and achieve adult body weight (≈20–30 g for females, 30–45 g for males) by 8–10 weeks.
How quickly do mice grow? - in detail
Mice reach a birth weight of approximately 1–2 g after a gestation period of 19–21 days. Within the first seven days, body mass typically triples to 5–6 g, reflecting a daily gain of about 0.7 g. By two weeks of age, weight averages 10–12 g, and at three weeks—around the usual weaning age—it reaches 15–18 g. After weaning, growth decelerates; most individuals attain their adult mass of 20–30 g between 6 and 8 weeks of age.
Key growth milestones:
- Day 0 (birth): 1–2 g; eyes closed, hair absent.
- Day 7: 5–6 g; fur begins to appear, eyes open.
- Day 14: 10–12 g; incisors erupt, locomotor activity increases.
- Day 21 (weaning): 15–18 g; solid food intake replaces maternal milk.
- Week 6–8 (sexual maturity): 20–30 g; reproductive capacity established.
Growth velocity is highest during the first two weeks, averaging 0.7–1.0 g per day, then declines to 0.2–0.3 g per day after weaning. Factors that modify these rates include genetic strain (e.g., C57BL/6 versus BALB/c), sex (males often grow slightly larger), ambient temperature, and nutrient density of the diet. Elevated ambient temperatures (22–24 °C) and protein‑rich chow (≥20 % protein) can increase daily weight gain by 10–15 % during the pre‑weaning phase.
Longitudinal studies using weekly weighing protocols confirm a sigmoid growth curve: rapid early ascent, a plateau approaching adult size, and a final stabilization phase. Accurate monitoring of this curve is essential for experimental designs that rely on age‑matched cohorts, as variations of a few days can translate into measurable differences in body composition and physiological parameters.