EFFECT OF A TRANSCERVICAL INFUSION OF SEMINAL PLASMA PRIOR TO INSEMINATION ON THE FERTILIZING COMPETENCE OF LOW NUMBERS OF BOAR SPERMATOZOAAT CONTROLLED AI-OVULATION INTERVALS

Dilution of boar ejaculates for use in artificial insemination reduces the amounts of seminal plasma components which have important regulat ive functions in fertilisation. The effects of a transcervical infusio n of 50 ml of seminal plasma immediately before insemination on fertil isation rates and accessory sperm counts of day 3-5 embryos were inves tigated using 0.5 X 10(9) (Experiment 1, n = 33 gilts), 0.3 X 10(9) (E xperiment 2, n = 20 gilts), or 0.5 X 10(9) spermatozoa with extended i nsemination-ovulation intervals to median values of 20 h (Experiment 3 , n = 32 gilts). The gilts were inseminated either 24 h after the dete ction of spontaneous oestrus (Experiments 1 and 2) or 24 h after human chorionic gonadotrophin (hCG) injection following hormonal synchronis ation of oestrus (Experiment 3). The time of ovulation was detected by transcutaneous sonography carried out at 8 h intervals. Fertilisation rates were not affected by the infusion of seminal plasma. In Experim ent 1, seminal plasma led to a significant shift towards zona classes with higher numbers of accessory spermatozoa compared with the control group. In Experiments 2 and 3, there was no difference in accessory s perm counts between gilts treated with seminal plasma and control gilt s, Using 0.3 X 10(9) spermatozoa (Experiment 2) the percentage of dege nerated embryos increased significantly but showed similar numbers of accessory spermatozoa as normal embryos, This indicates that less comp etent spermatozoa fertilised the oocytes, which showed reduced ability to sustain embryonic development. It is concluded that infusions of s eminal plasma are less effective for optimising conditions for fertili sation when conducted prior to insemination (24 h after the detection of oestrus) than at the onset of oestrus, which leads to an advancemen t of ovulation.