How do mice breed in captivity? - briefly
In a controlled environment, breeding pairs are placed together in a cage with ample nesting material, a balanced diet, and a 12‑hour light/dark cycle. Females typically give birth to 5–10 pups after a 19‑day gestation, and litters are weaned at three weeks before the parents are separated to prevent aggression.
How do mice breed in captivity? - in detail
Mice kept under controlled conditions reproduce through a series of well‑defined steps. Successful propagation requires careful management of genetics, environment, nutrition, and health monitoring.
A breeding pair is formed after accurate sex identification. Neonatal mice are sexed by examining anogenital distance; males possess a longer distance and visible testes after three weeks. Only healthy, mature individuals—typically 8–12 weeks old—are selected to avoid inbreeding and to ensure reproductive vigor.
Environmental parameters must remain stable. Temperature should be maintained at 20–24 °C, relative humidity at 40–60 %, and a 12‑hour light/dark cycle provided to synchronize hormonal cycles. Cages are equipped with nesting material, a solid floor, and adequate ventilation to reduce stress and prevent respiratory disease.
Nutrition plays a critical role. Breeding stock receives a high‑calorie diet enriched with protein (18‑20 %), fat (5‑7 %), and essential vitamins. Fresh water is supplied ad libitum, and supplemental treats such as soy or sunflower seeds may be offered during gestation to support fetal growth.
The breeding process proceeds as follows:
- Pairing – Place one male and one female together in a clean cage; monitor for mating behavior (mounting, vocalizations).
- Mating confirmation – Presence of a copulatory plug or sperm in vaginal smears indicates successful copulation.
- Gestation – Lasts 19–21 days; females exhibit nesting behavior and may gain up to 10 % body weight.
- Parturition – Litters typically contain 5–8 pups; newborns are altricial, hairless, and blind.
- Litter care – Provide additional nesting material; avoid handling for the first 48 hours to reduce maternal stress.
- Weaning – Occurs at 21 days; pups are separated by sex and transferred to individual cages with age‑appropriate feed.
- Record‑keeping – Document dates of pairing, birth, litter size, weight at birth and weaning, and any health issues for each cohort.
Health surveillance includes routine screening for common pathogens (e.g., Mycoplasma pulmonis, Sendai virus) and observation for signs of distress, such as excessive grooming, weight loss, or abnormal posture. Quarantine new arrivals for at least two weeks before introduction to the breeding colony.
Genetic management involves rotating breeding pairs, maintaining pedigree records, and preventing accidental homozygosity. When specific traits are desired, selective breeding protocols—backcrossing, outcrossing, or using marker‑assisted selection—are applied under strict ethical guidelines.
By adhering to these protocols, mouse colonies can achieve high reproductive efficiency, stable genetic lines, and minimal morbidity, supporting reliable experimental outcomes and long‑term colony sustainability.