THE INITIAL FERTILIZING-CAPACITY OF LONG-TERM-STORED LIQUID BOAR SEMEN FOLLOWING PREOVULATORY AND POSTOVULATORY INSEMINATION

In pigs, high variation is seen in the duration of estrus and in the t ime of ovulation. This is one of a wide range of factors not related t o semen quality, which possibly influences the results of field insemi nation trials. Experiment 1 (n=81 gilts) was performed to determine th e influence of the time of owlation on the fertilizing capacity of liq uid boar semen stored up to 118 h. The objective of Experiment 2 (n=10 2 gilts) was to study the fertilizing potential of semen stored up to 120 h in 2 different extenders, Androhep and Beltsville Thawing Soluti on (BTS), by means of postovulatory AI. Inseminations were performed 0 to 4 h after ovulation in order to standardize the trial conditions. Fertilization rates based on Day-2 to Day-4 embryos, and the number of accessory spermatozoa per zona pellucida did not differ between semen stored for 0 to 48 and 48 to 87 h in gilts ovulating within 12 after insemination (Experiment 1). Gilts with an interval of 12 to 24 h betw een AI and ovulation had lower fertility results using semen stored fo r more than 48 h. A further decrease was observed when semen storage e xceeded 87 h in those gilts ovulating later than 24 h after inseminati on. The time of owlation has to be considered as being a major factor of variation in the fertility results of AI trials. In Experiment 2, f ertilization rates and numbers of accessory spermatozoa decreased betw een semen stored for 0 to 24 and 24 to 48 h in BTS, and between semen stored for 0 to 24 and 48 to 72 h in Androhep. Significant differences in fertility between diluents were seen only when using semen stored for more than 96 h, with semen extended with Androhep giving the highe r results. The results indicate that the decrease in fertilizing capac ity due to in vitro aging of spermatozoa cannot be prevented even duri ng the first days of storage.