Boar spermatozoa have been shown to be capacitated without preincubation if the fertilization medium contains caffeine and a high concentration of Ca2+, but the incidence of polyspermy in IVM-IVF oocytes is still high (60%-100%). To prevent polyspermy, co-culture with oviductal cells, preincubation with porcine follicular fluid, or the addition of oligopeptides in the fertilization medium, have been tested with significant effects but still remarkably high rates of polyspermy (32%-58%). On the other hand, techniques for in-vitro maturation of porcine oocytes have progressed such that the problem of the low rate of pronucleus formation with in-vitro matured oocytes after IVF has been nearly solved. Irrespective of the collection method porcine follicular oocytes are morphologically selected based on the morphology of cytoplasm and cumulus cells and can be matured in vitro in a static system or in the non-static shaking culture system with addition of follicle cells and a high percentage of oocytes with both male and female pronuclei is observed. Beneficial effects of gonadotrophins, estradiol-17 beta, porcine follicular fluid and/or cysteine on maturation of oocytes have been reported. However, the number of piglets obtained from IVM-IVF oocytes is low. Possible experimental strategies to improve success rates of porcine IVM-IVF are discussed.
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