Reproductive performance in C57BL and I strain mice

Area of Science:

• Laboratory Animal Science
• Reproductive Biology
• Nutritional Science

Background:

• I strain mice exhibit poor reproductive performance compared to control C57BL mice.
• This includes fewer productive matings, smaller litter sizes, and reduced survival to weaning.
• The overall productivity of I strain dams is approximately half that of C57BL dams.

Purpose of the Study:

• To investigate the causes of poor reproductive performance in I strain mice.
• To identify potential dietary interventions to improve breeding success.

Main Methods:

• Analysis of historical breeding records from multiple institutions for I strain and C57BL mice.
• Comparison of reproductive data with dietary studies, specifically focusing on pyridoxine (PN) supplementation.
• Evaluation of litter size, mating success, and offspring survival rates.

Main Results:

• I strain mice showed significantly lower reproductive output than C57BL mice.
• Slightly increased dietary pyridoxine (8-12 mg/kg) improved I strain reproductive performance.
• Very high levels of pyridoxine (410-1230 mg/kg) did not further enhance I strain productivity but improved C57BL survival, suggesting other dietary factors may be limiting for I strain mice.
• Improved reproductive performance in I strain mice correlated with diets promoting higher body weight.

Conclusions:

• Poor reproductive performance in I strain mice is multifactorial, involving mating and littering issues.
• Dietary pyridoxine levels, within a specific range, can partially ameliorate these reproductive deficits.
• Further research is needed to identify other limiting dietary factors for I strain mice reproduction.