| Abstrakt: |
The female chinese (C.) Hamster () exhibits a progressive decline in litter size after the third litter. The mean number of litters produced was 4.9 ± .5 for 25 c. Hamsters, and the mean age of the C. Hamsters at the time of delivering the last litter was 16.4 ± .5 months. Most aged C. Hamsters (17 to 20 months old) retained a relatively normal estrous cycle, although fewer ovulated, either spontaneously or after mating, when compared with younger hamsters (5 to 6 months old). Progesterone injections given to aged (16 to 21 months old), otherwise nonproducing, c. hamsters after mating permitted 61% to become pregnant once again and 34% to deliver viable young. Early infant mortality in these litters was greatest, however, and growth of the young was retarded in comparison with earlier litters. It appears as if agerelated changes in the ovary and uterus are primarily responsible for reproductive senescence in the female C. hamster. [ABSTRACT FROM PUBLISHER] |
