Unveiling the Secrets of Mouse Pregnancy: A Comprehensive Guide for Researchers and Breeders

The study of mouse pregnancy is crucial for understanding fundamental reproductive processes, assessing developmental toxicity, and advancing biomedical research. Mice have become the preferred experimental model for pregnancy due to their relatively short gestation period, high fecundity, and genetic malleability. This guide provides a comprehensive overview of mouse pregnancy, from pre-conception to parturition, to empower researchers and breeders with the knowledge and techniques necessary for successful investigations.

Pre-Conception Considerations

Age and Weight: Female mice are sexually mature between 6-8 weeks of age. However, optimal breeding occurs when females weigh at least 20 grams.

The Guide to Investigation of Mouse Pregnancy

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Estrus Cycle: Mice exhibit a 4-5 day estrus cycle, characterized by a period of receptivity to mating. Estrus can be detected by vaginal cytology or by observing the presence of a vaginal plug after mating.

Mating and Fertilization

Natural Mating: Male and female mice can be housed together for natural mating. The presence of a vaginal plug indicates successful mating.

Artificial Insemination (AI): AI can be performed using collected sperm. Techniques include intrauterine or intravaginal insemination.

Pregnancy Diagnosis and Monitoring

Clinical Signs: Pregnancy can be suspected around 10-12 days post-mating. Visible signs include abdominal enlargement, weight gain, and changes in posture.

Ultrasonography: Ultrasound imaging can provide early confirmation of pregnancy, typically from day 10 onwards, by detecting gestational sacs and fetal heartbeats.

Palpation: Experienced breeders can gently palpate the abdomen to feel the presence of palpable embryos around day 12-14 of pregnancy.

Gestation and Fetal Development

Gestation Period: The average gestation period for mice is 19-21 days. Development is divided into four stages: pre-implantation, organogenesis, fetal growth, and maturation.

Embryonic Development:

• Day 1-5: Pre-implantation period, embryo develops within the fallopian tube.
• Day 6: Implantation into the uterine lining.
• Day 7-11: Organogenesis, formation of major organs and tissues.

Fetal Development:

• Day 12-15: Fetal growth period, rapid increase in size and differentiation.
• Day 16-19: Maturation period, development of hair, claws, and whiskers.

Parturition and Postpartum Care

Labor and Delivery: Typically occurs at night. Signs include nesting, restlessness, and abdominal contractions.

Litter Size: Average litter size ranges from 5-12 pups.

Postpartum Care:

• Nursing: Female mice provide milk for their pups, which begin nursing shortly after birth.
• Cleaning and Nesting: Female mice clean and build nests for their pups.
• Weaning: Pups are typically weaned around 3-4 weeks of age.

Ethical Considerations

Animal Welfare: Researchers must prioritize the well-being of the animals involved in mouse pregnancy studies.

Institutional Review: Institutional Animal Care and Use Committees (IACUCs) review and approve research protocols to ensure ethical and humane treatment of animals.

Understanding mouse pregnancy is essential for advancing medical research and developing new reproductive technologies. This comprehensive guide provides researchers and breeders with the necessary knowledge and techniques to conduct successful investigations. By adhering to ethical principles and utilizing appropriate methods, researchers can unlock the full potential of this valuable experimental model.

References

• Brown, D. M., & Moore, H. D. (2012). Laboratory mouse handbook: Genetics, breeding and management (No. 4). Elsevier.
• Hollinshead, M., & Tilford, C. A. (2007). Mouse estrus cycles: Characterization of vaginal cytology, behavior, and ovarian histology during the estrus cycle and after ovariectomy. Biology of Reproduction, 77(6),893-900.
• Humason, G. L., & Lushbaugh, C. C. (1979). Animal tissue techniques. WH Freeman and Company.

The Guide to Investigation of Mouse Pregnancy

4.4 out of 5

Language	:	English
File size	:	20342 KB
Text-to-Speech	:	Enabled
Screen Reader	:	Supported
Enhanced typesetting	:	Enabled
Print length	:	832 pages

FREE