Some factors influencing the interaction of ram spermatozoa with zona-free hamster eggs

Variability in the interaction of ram spermatozoa with zona-free hamster eggs was recorded not only amongst individual males but also between the first and second ejaculates of the same male collected 30 min apart. Fusion ability also differed according to the conditions of gamete mixing. This ability decreased after in-vitro storage of undiluted ejaculates at room temperature but lasted for 48-192 h. The kinetics of sperm-egg fusion during the time of gamete incubation varied not only with the time of sperm storage in vitro but also with the ejaculate. When the semen was frozen, the ability of the spermatozoa to fuse was markedly reduced.