Comparison of two bedding types on the breeding fecundity of C57BL/6J mice

One of the favored options for generating complex transgenic laboratory mice is through in-house breeding and management strategies. One consideration in the management of these colonies is how the animals' environment may affect reproductive success. Several aspects of the microenvironment can be controlled or manipulated, including cage type, bedding, enrichment, diet, and temperature and humidity. This study sought to evaluate reproductive outcomes for C57BL/6J mice that were randomly assigned to one of two different bedding types: paper based or corncob bedding. Our hypothesis was there would be no significant difference in reproductive outcomes between the two bedding types. A total of 10 males and 10 females were paired at 45 days of age. Animals were allowed to breed for 15 consecutive weeks. Cages were checked daily for the presence of pups and a pup count was performed at 7 days of age. Weaning occurred at 20 or 21 days of age, at which time a final pup count, pup weight, and sex were recorded. All litters born and pups weaned in the 15-week timeframe were used for data analysis. Statistical analysis compared cannibalization between the two groups and the results showed no statistical difference between groups (p > 0.05). Other parameters analyzed included average litter size, average weaning weight, and number of litters per group. All pups counted at Day 7 survived to weaning age in both groups. We concluded that both bedding types produced similar success regarding breeding fecundity in C57BL/6J mice.