When do rats become sexually mature? - briefly
Female rats attain sexual maturity at approximately 5–6 weeks of age, while male rats mature slightly later, around 6–8 weeks. This timing marks the onset of reproductive capability in laboratory strains.
When do rats become sexually mature? - in detail
Rats attain reproductive capability during the post‑natal period known as puberty. In most laboratory strains, females reach this stage between 35 and 45 days of age, while males typically mature slightly later, around 45 to 55 days. The transition is marked by the first estrous cycle in females and the appearance of spermatozoa in the epididymis of males.
Key physiological indicators include:
- Hormonal surge: Rising levels of luteinizing hormone (LH) and follicle‑stimulating hormone (FSH) precede gonadal activation.
- Gonadal development: Ovarian follicles progress to the pre‑ovulatory stage; testes show seminiferous tubule maturation and spermatogenesis.
- External signs: Vaginal opening in females and increased body weight (approximately 150 g for females, 200 g for males) accompany internal changes.
Factors influencing the timing are:
- Strain genetics: Sprague‑Dawley and Wistar rats mature earlier than Long‑Evans or Fischer 344 strains.
- Nutrition: Adequate protein and caloric intake accelerate development; caloric restriction delays it.
- Environmental conditions: Temperature, lighting cycles, and social housing affect hormonal rhythms and can shift onset by several days.
Experimental confirmation typically involves daily vaginal cytology for females and periodic epididymal sperm counts for males. Monitoring these parameters provides precise determination of the age at which rats become reproductively competent.