Developmental competence, after transfer to recipients, of porcine oocytesmatured, fertilized, and cultured in vitro

The objective of this study was to evaluate the developmental ability of ea rly porcine embryos produced in vitro and transferred to recipient gilts. P orcine cumulus-oocyte complexes were matured in modified North Carolina Sta te University-37 solution for 44-46 h (in vitro maturation, IVM). In vitro fertilization (IVF) was performed with frozen-thawed epididymal spermatozoa . Inseminated oocytes were cultured in vitro (IVC) for 0, 24, or 48 h in mo dified NCSU-37 solution. Embryos were surgically transferred to the oviduct s of recipients in which estrus had been synchronized with eCG and hCG. On the 29th day post-IVF, the uteri of some recipients were surgically examine d for pregnancy; then pregnant females were hysterectomized in order to exa mine number and weight of the fetuses. Developmental rates to fetuses for I VM/IVF oocytes cultured for 24 and 48 h were significantly lower (p < 0.05, 1.7% and 2.0%, respectively) than that of IVM/IVF oocytes without IVC (6.7 %). However, the weights of fetuses (1.0-1.2 g) did not differ among the ex perimental groups. The other recipients were examined for pregnancy using a n ultrasound pregnancy detector, and pregnant females were allowed to go to term. Healthy piglets were delivered by some recipients to which embryos c ultured for 0 or 24 h had been transferred; however, no farrow was obtained from embryos cultured for 48 h before the transfer. The results indicate t hat the viability of in vitro-produced porcine embryos is decreased by IVC after IVF; however, these embryos have competence to develop to term. An im proved IVC system of porcine IVM/IVF oocytes is needed to generate advances in this field.