How many days does it take for a rat to grow? - briefly
A rat reaches sexual and physical maturity in roughly five to six weeks after birth. This equates to about 35–42 days.
How many days does it take for a rat to grow? - in detail
Rats reach full physiological maturity within a predictable period that can be divided into distinct stages.
The prenatal phase lasts about 21‑23 days. After birth, pups are altricial: eyes open at 13‑15 days, fur appears around day 10, and they begin crawling independently by day 10‑12.
Weaning occurs between days 21 and 28, when solid food replaces maternal milk. At this point, growth accelerates; body weight typically doubles each week for the first three weeks. By day 30, most individuals attain approximately 70‑80 % of adult mass.
Sexual maturity is achieved around day 45‑55 for males and day 35‑45 for females, depending on strain and environmental conditions. Full adult size, including skeletal development and stable weight, is usually observed by day 70‑90.
Factors influencing the timeline include:
- Strain: Laboratory strains (e.g., Sprague‑Dawley, Wistar) mature slightly faster than wild‑type rats.
- Nutrition: High‑quality diets shorten the growth period; caloric restriction delays it.
- Temperature: Ambient temperatures above 22 °C promote faster development; lower temperatures slow metabolism.
- Health status: Disease or stress can extend the maturation window.
In summary, a rat progresses from conception to adult form in roughly 10‑13 weeks, with key milestones at 3 weeks (weaning), 5‑8 weeks (sexual maturity), and 10‑13 weeks (full adult size). Adjustments to these estimates are required when accounting for specific genetic lines or husbandry conditions.