EFFECT OF TIME OF INSEMINATION RELATIVE TO OVULATION ON FERTILITY WITH LIQUID AND FROZEN BOAR SEMEN

Precise data on fertility results following peri- and postovulatory in semination in spontaneously ovulating gilts is lacking. Using transcut aneous sonography every 4 h during estrus as a tool for diagnosis of o vulation, the effects of different time intervals of insemination rela tive to ovulation were investigated with liquid semen (Experiment 1, n =76 gilts) and frozen semen (Experiment 2, n=80 gilts). In Experiment 3 (n=24 gilts) the number of Day-28 embryos related to the various int ervals between insemination and ovulation was determined after the use of liquid semen. Using liquid semen the fertilization rates based on Day-2 to Day-5 embryos and the number of accessory spermatozoa decreas ed significantly in gilts inseminated with 2 x 10(9) spermatozoa per d osage in intervals of more than 12 h before or more than 4 h after ovu lation. In the time interval 4 to 0 h before ovulation, comparable fer tilization rates were obtained using frozen semen (88.1%) and liquid s emen (92.5%). Fertilization rates and numbers of accessory spermatozoa decreased significantly when gilts were inseminated with frozen semen more than 4 h before or 0 to 4 h after the detection of ovulation. Th e percentage of Day-28 embryos was significantly higher following preo vulatory insemination compared to inseminations 0 to 4 h and 4 to 8 h after ovulation. It is concluded that the optimal time of insemination using liquid semen is 12 to 0 h before ovulation, and 4 to 0 h before ovulation using frozen semen. The results stress the importance of fu rther research on sperm transport and ovulation stimulating mechanisms , as well as studies on the time of ovulation relative to estrus-weani ng intervals and estrus duration.