How do domestic rats grow? - briefly
Domestic rats experience rapid post‑natal growth, attaining sexual maturity within 5–8 weeks and an adult weight of 300–500 g, varying by strain and nutrition. Their development follows a predictable sequence of weaning, skeletal maturation, and reproductive organ enlargement.
How do domestic rats grow? - in detail
Domestic rats progress through three distinct phases: neonatal, juvenile, and adult.
During the neonatal stage (birth to 3 weeks), pups are altricial, blind, and hairless. Their body weight typically doubles each week, reaching approximately 15–20 g by the end of the third week. Nutrition comes exclusively from the dam’s milk, which supplies high levels of protein (≈20 %), fat (≈10 %), and essential micronutrients. The temperature of the nest must remain between 28–30 °C to support thermoregulation.
The juvenile period (3 weeks to 8 weeks) marks the onset of solid food intake. By week 4, pups begin exploring the cage, consuming a balanced grain‑based diet containing 18–20 % protein, 4–5 % fat, and adequate calcium/phosphorus (1.2 %/0.9 %). Growth rate accelerates, with average weight gain of 5–7 g per week, reaching 80–120 g at sexual maturity. Skeletal development proceeds rapidly; the epiphyseal plates close around week 10, indicating the end of longitudinal bone growth.
The adult phase commences after sexual maturity (8–12 weeks). Body weight stabilizes between 300 and 500 g, depending on strain and sex. Growth plates are fully ossified, and further size increase occurs only through increased muscle mass and adipose tissue, contingent on diet composition and activity level.
Key factors influencing growth:
- Genetics: Strains such as Sprague‑Dawley mature faster than Long‑Evans, showing earlier peak weight.
- Diet quality: Protein content above 20 % can accelerate early growth; excess fat leads to adiposity without proportional skeletal gain.
- Environmental temperature: Ambient temperatures below 20 °C reduce feed intake and slow weight gain; temperatures above 30 °C may cause heat stress and growth retardation.
- Health status: Parasitic infections, respiratory disease, or gastrointestinal disturbances can cause weight loss of 5–10 % within days.
- Social dynamics: Overcrowding reduces individual feed access, lowering average weekly weight gain by 1–2 g.
Monitoring growth involves weekly weighing, assessing body condition score, and measuring crown‑rump length. Deviations of more than 10 % from the expected growth curve warrant veterinary evaluation. Proper husbandry—consistent nutrition, stable temperature, and disease prevention—ensures that domestic rats achieve their genetic growth potential.