Fertility of fresh and frozen rabbit semen inseminated at different times is indicative of male differences in capacitation time.

Some reports indicate that sperm from different males differ in capacitation time, and other reports suggest thaifreezing sperm may affect their capacitation time. These Iwo variables were specifically studied in rabbits in a frrtilily trial with 96 does inseminated with approximately 1.6 million motile fresh or frozen sperm from three different bucks at 15,10,5, and 0 h before expected ovulation. Fresh semen averaged 84% live (unstained) sperm and 88% had normal acrosomes; corresponding valuesforfrozen sperm were 44% and 54%. On the basis of does that became pregnant, average litter size with fresh semen was 5.5 and with frozen semen was 4.8 (p>O.O5), bat overall, does bred with frozen semen producedfewer young (p 0.OS). Bucks and time of insemination affected both the proportion of does that were pregnant and litter size (pinsemination (pinsemination.