Effects of semen components on ovulation and fertilization.

In pigs, transcervical infusion of seminal plasma at the onset of oestrus advances ovulation and thus improves the chance of gametes meeting during their full fertilizing competence. An animal model that allows single uterine horn infusion was used in combination with transcutaneous sonographic monitoring of ovaries. Preparative surgery involved the detachment of one uterine horn from the corpus, leaving the caudal end open to the peritoneal cavity but sealing the corpus wound. Transcervical infusion of 100 ml seminal plasma immediately after the detection of oestrus advanced ovulation by between 8 and 14 h on the ipsilateral ovary adjacent to the infused horn compared with the contralateral ovary. In addition, the seminal plasma infusion did not influence the LH profile compared with uterine infusion of PBS. This finding indicates that the effect is mediated by a local mechanism in the female genital tract. The advancement of ovulation depends on the time of infusion early in oestrus and is more pronounced in gilts exhibiting a long interval between the onset of oestrus and spontaneous ovulation compared with early ovulators. At 24 h after the detection of oestrus, seminal plasma was ineffective. Apparently, seminal plasma does not affect maturation and fertilizing competence of oocytes. The activity resides in a low molecular mass protein fraction and, to a far lesser extent, in seminal oestrogens. Further characterization of the active components may allow a practical application in AI.