In vitro fertilization of rabbit eggs in oviduct secretions from different days before and after ovulation

In vitro fertilization of rabbit eggs in oviduct secretions has been studied through different days of the psudopregnant cycle. The appearance of the pronuclei and cleavage into two cells, which were the criteria of fertilization, occurred significantly less frequently when in vitro fertilization was attempted in the oviduct secretions obtained during the estrous (preovulatory) period of the cycle than it was in the secretions obtained during pseudopregnancy or in Brackett's medium plus 20% heated rabbit blood serum. Whether fertilization was attempted in ampulla secretions or in whole oviduct secretions had no effect on the success rate. The effects of oviduct secretions from the estrous period of the cycle is probably due mainly to an effect on the egg, involving the very first development processes during and after fertilization.