Distribution, number and membrane integrity of spermatozoa in the pig oviduct in relation to spontaneous ovulation

The pattern of distribution, number and membrane integrity of spermatozoa in the utero-tubal junction (UTJ) and isthmus during three oestrous stages were related to spontaneous ovulation in flushed and fixed oviducts of multiparous sows. Three unrelated boars were each used once to mate or artificially inseminate (neat ejaculate) six out of 18 sows, 18 h prior to expected ovulation. The sows were slaughtered 6–8 h before, during or 6–8 h after ovulation. The ad-uterine oviductal region (UTJ and isthmus) was divided into UTJ, lower isthmus, middle isthmus and upper isthmus segments. A higher fraction of middle and upper isthmus segments contained spermatozoa during the peri- and post-ovulatory periods than during the pre-ovulatory period. The distribution, numbers and membrane integrity of spermatozoa in the UTJ-isthmus region were influenced by the ovulation event. Numbers and distribution of spermatozoa varied depending on the boar used. The flushing technique allowed a better assessment of the distribution, number and membrane integrity of tubal spermatozoa than in situ observation with a scanning electron microscope (SEM).