NATURE OF LITTER SIZE LOSS IN SENESCENT HAMSTERS

Young and senescent female hamsters were sacrificed on days 8, 10, 12, 14 and 15 of pregnancy, and the number of viable and resorbing conceptuses was determined. The ovulation rate for each group was also recorded. At each day, there was a reduction in the litter size in senescent animals as compared to the young, but the number of ovulations in each age group was equal. The results indicated that the litter size loss, in senescent hamsters, is not due to a reduction in the ovulation rate, but to a seven fold increase in preimplantation deaths and to a two fold increase in resorption. Copyright © 1969 Wiley‐Liss, Inc.