Selection based on morphological features of porcine embryos produced by in vitro fertilization: Timing of early cleavages and the effect of polyspermy.

The aim of this study was to examine whether a morphological approach is efficient for selecting high-quality porcine embryos produced by in vitro fertilization (IVF) under high polyspermy conditions. Frozen-thawed Meishan epididymal spermatozoa showing moderate and high polyspermy were subjected to IVF (1 × 10  sperms/ml). Under conditions of moderate polyspermy, 4-cell embryos selected at 48 hr after IVF (single selection) and 8-cell embryos selected at 79 hr after IVF from the collected 4-cell embryos (double selection) showed high developmental competence. Likewise, 4- and 8-cell embryos produced by IVF under high polyspermy conditions also showed high competence for development to blastocysts. However, blastocysts derived from high polyspermy conditions had significantly fewer cells than those produced under moderate polyspermy conditions. Furthermore, the frequency of nuclear and chromosomal abnormalities in 4- and 8-cell embryos produced under conditions of high polyspermy was significantly (p < .05) higher in comparison to moderate polyspermy conditions. These findings suggest that although high polyspermy affects the frequency of nuclear and chromosomal anomalies in porcine IVF embryos, subsequent selection based on morphological features of 4- and 8-cell embryos even under high polyspermy conditions, could be an alternative option for selecting porcine IVF embryos with high development ability.