The effect of mating female rats at 35 or 80 days of age on pup production and maternal weight

Abstract

SUMMARY2 groups of 10 rats each were mated for the 1st time at 35 days and 80 days respectively. At 106 days of age the early-mating group had produced 233 pups, whilst the other group had produced 99 pups. Pups produced from the early litters were not smaller than those produced later, but individual litters were smaller. The size of the litter increased with parity. The weight of dams in both groups was similar at 106 days of age.

Exteroceptive Factors, Sexual Maturation and Reproduction in the Female Rat

“…Moreover, their fecundity compared favourably with that of older primagravidae in our colony. Whereas some workers have not found any significant differences in litter size between very early and later bred females in the rat (Pritchard & Tucker, 1970;Rutledge et al, 1974) and mouse (Eisen, 1973), others have reported that younger female mice (Kennedy, 1973) and rats (Kali & Amir, 1973) are less fecund. We found that young conceived at the 1st oestrus showed a very high rate of survival to weaning, indicating that the younger, smaller female was able to cope with lactational demands.…”