FREQUENCY AND EXTENT OF DELAYED IMPLANTATION IN LACTATING RATS AND MICE

摘要: Rats and mice ovulate are receptive to males on the 1st or 2nd night following parturition. An animal may thus be pregnant while it is lactating, but implantation often delayed (Lataste, 1891). In general, appears that length of delay in correlated with number suckling young (Enzmann, Saphir & Pincus, 1932). The data concerning lactating rats have been collected from relatively small numbers experimental animals. Charles River Breeding Laboratories, a commercial producer for scientific research, made available us breeding records larger population which possible estimate frequency delay. One pair CD* (derived Sprague-Dawley) CD*-1 I.C.R. Swiss albino) was housed each cage. Since male female remained together cage even during parturition lactation, there maximal opportunity mating occur post-partum oestrus. Rat litters were removed at 21 days age, 19 age. record included, besides other information, date birth litter size litter. From total between births series born pair, calculate approximate except first