IN SYNCHRONIZED PIGS, THE DURATION OF OVULATION IS NOT AFFECTED BY INSEMINATION AND IS NOT A DETERMINANT FOR EARLY EMBRYONIC DIVERSITY

The duration of ovulation (i.e., the time interval between the ovulati on of the first and the last follicle in a sow during an estrus) is sa id to be related to embryonic diversity, which in turn is related to e mbryonic mortality. The relationship between the duration of ovulation and within-litter early embryonic diversity and the influence of inse mination on the duration of ovulation were studied. To determine wheth er ovulation assessment (transrectal ultrasonography) influenced early embryonic development, control sows were not scanned. Multiparous cyc lic sows with an exogenously induced estrus were used. Ovulation detec tion by means of transrectal ultrasonography did not influence fertili zation rate, accessory sperm count, early embryonic development or ear ly embryonic diversity, and, therefore, ultrasonography appears to be a worthwhile method for studying the time and duration of ovulation. I nsemination did not influence (P>0.05) the duration of ovulation, in s ows which ovulated between 39 and 49 hours after hCG injection. The du ration of ovulation (mean+/-SD(range)) was 2.4+/-0.7 (1.1 to 4.0) hour s in 15 sows which were artificially inseminated at 22 and 30 hours af ter hCG injection. In 8 noninseminated sows, the duration of ovulation was 2.3+/-0.5 (1.5 to 3.3) hours. The duration of ovulation was not r elated to embryonic diversity (SD of the number of nuclei or the numbe r of cell cycles of embryos in a litter) at 114 to 121 hours after ovu lation. Thus, a difference of up to 3 hours in the duration of ovulati on does not seem to be an important determinant of variation in embryo nic diversity between sows.