雌雄同居 (1: 1) 飼育によるSPF C3Hマウスの繁殖成績と寿命について

Deta are presented on lifetime reproductive performance (number of fertile matings, litters and mice born and weaned) and lifespan of C3Hf/HeMsNrs reared under specific pathogen free conditions. Thirty pairs of mice were mated at the age of 64±5 days and maintained under a single pair mating system until either of pair died. No mice died before termination of their reproductive life, therefore, the data of reproductive performance ara based on 30 monogamous pairs. Twenty four pairs out of 30 pairs could produce at least the 6th litters. In relation to the age of females, 82 % of a total of 210 litters and 87 % of a total of 1, 226 offsprings were produced until the age of 250 days. The females gave a maximum litter size, 6.9 at the age between 101 and 150 days. Sex ratio of offsprings did not vary with the age of the females at littes and the parity. It is, however, noteworthy that, when the sex ratio is calculated on mating pair basis it significantly differs from expected ratio of one to one in 5 pairs out of 30 pairs. Among mating pairs, a total number of litters per pair ranged from 3 to 10 litters and a mean total number of offsprings was 41 mice. The ages of females at the last litter born ranged from 128 to 352 days (mean 261 days) . The mean lifespan for females and males were 737 and 731 days, respectively. It was not found that there is any correlation between lifespan and lifetime reproductive performance.