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Due to the long interval from onset ofstanding oestrus to ovulation in the pig, a reservoir is needed in which spermatozoa can be stored prior to ovulation.The main objectives ofthe work described in this thesis were to i) determine whether it would be possible to use information from a previous oestrus to predict the time of ovulation in the next oestrus, ii) investigate how sperm distribution and membrane integrity of spermatozoa present in the utero-tubal junction (UTJ) and isthmus, are affected by ovulation, iii) examine changes in morphology and localisation of spermatozoa in vasculary perfusion-fixed UTJ and isthmus around ovulation, iv) study the effects offood deprivation during the post-ovulatory period on cleavage rate, numbers of accessory spermatozoa in the zona pellucida and hormonal profiles in multiparous sows. In the 44 multiparous sows studied ovulation was determined by transrectal ultrasonography. Time lapsed from onset of standing oestrus to ovulation in two consecutive oestruses did not differ significantly. Ovulation during the second oestrus after weaning could therefore be predicted using the onset of standing oestrus as a reference point.The sows were inseminated with neat semen 18 h prior to expected ovulation. The distribution pattern, number and viability of spermatozoa in the UTJ and isthmus were related to ovulation in flushed and fixed oviducts. Sperm numbers diminished gradually along a gradient from UTJ to the isthmus during the pre-ovulatory period. Ovulation reduced the numbers of viable spermatozoa in the UTJ and isthmus, and was related to the relocation of spermatozoa and reduction of intraluminal fluid masses. Scanning electron microscopy revealed the presence oftwo populations ofspermatozoa in the reservoir, one with epithelial contact and the other without. Transmission electron microscopy studies showed that spermatozoa attached to the epithefiuih had intact plasma membranes prior to ovulation, whereas they were broken afterwards.Food deprivation for about 48 h, starting immediately after ovulation, reduced the numbers of viable spermatozoa in the UTJ and isthmus, measured indirectly by counting the numbers of accessory spermatozoa in the zona pellucida, and lowered the cleavage rate of fertilized ova recovered at a mean of 79 ± 3.4 h after ovulation. During the period of food deprivation, plasma levels of insulin were low, while those of cortisol, progesterone and prostaglandin F2a metabolite (PG-metabolite) were elevated. Thus, food deprivation was associated with changes in the secretion of metabolic and reproductive hormones, which might have modulated the oviductal environment affecting the embryos as well as the spermatozoa in the oviduct. |
