Lipoproteins, isolated from ostrich egg yolk (LPFo), provide excellent protection for boar spermatozoa against cryo-induced damage. The present study was performed to investigate the effects of LPFo on the freezability and fertilizing capacity of frozen-thawed (FT) boar semen after post-cervical artificial inseminations (post-CAIs). Semen, collected from 7 Polish Large White (PLW) and 4 Polish Landrace (PLR), was frozen in an extender containing LPFo. Post-CAIs were performed in 38 multiparous sows, using a catheter-cannula kit. Sows were inseminated 2× within one oestrus, and fertility parameters were recorded after farrowing. Neither boar (within breed) nor breed affected the quality of the pre-freeze (PF) semen, such as total motility (TMOT), mitochondria membrane potential (MMP), plasma membrane integrity (PMI), osmotic resistance test (ORT) and DNA fragmentation. Differences in the freezability of boar semen were observed among the boars, whereas there were no marked breed effects. Post-thaw TMOT markedly declined over storage time in most of the boars, particularly at 60 min after thawing. Inseminations of post-weaned oestrus sows resulted in pregnancy and farrowing rates of 84.2% and 81.6%, respectively. Neither the mean number of piglets born (NB) nor the mean number of piglets born alive (NBA) was affected by boar or breed. The total number of piglets born was 365, resulting in 11.8 NB piglets, whereas the total number of piglets born alive was 353, with 11.4 NBA piglets per litter. The findings of this study reaffirm the variations in the freezability of boar semen. In this study the supplementation of ostrich egg yolk lipoproteins to the freezing extender of boar semen produced high proportions of functionally viable FT spermatozoa that were capable of providing acceptable fertility results after post-CAIs in multiparous sows.
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