How much does a one-month-old rat weigh? - briefly
A rat that is roughly four weeks old usually weighs between 30 g and 50 g, with most laboratory strains averaging around 35 g. Variations depend on genetics, nutrition, and sex.
How much does a one-month-old rat weigh? - in detail
A rat that is approximately four weeks old typically weighs between 30 g and 80 g. The exact figure depends on several variables:
- Strain: Laboratory strains such as Sprague‑Dawley or Wistar often fall near the upper end of the range (60‑80 g), while smaller strains like the Long‑Evans or wild‑caught specimens may be closer to 30‑50 g.
- Sex: Males usually gain weight faster than females, resulting in a 5‑10 g difference at this stage.
- Nutrition: Access to a balanced pelleted diet yields weights near the median of the range; calorie‑restricted or low‑protein feed can reduce growth by 10‑15 %.
- Housing conditions: Ambient temperature, cage enrichment, and stress levels influence metabolism and thus body mass.
Growth curves for common laboratory rats show a rapid increase during the first month, with an average daily gain of about 1.5 g to 2 g. By the end of week four, the weight trajectory begins to plateau as the animal approaches sexual maturity.
Weight measurement is most accurate with a calibrated analytical balance, recording to the nearest 0.1 g. Repeated measurements over several days reduce variability caused by intestinal content and hydration status.
In summary, a four‑week‑old rat’s mass is generally 30‑80 g, with the precise value determined by genetic background, gender, diet, and environmental factors.