Evaluation of pig oocyte in vitro maturation and fertilization using three gonadotropin-based hormonal compounds

Abstract

Objective: To evaluate the effect of human chorionic gonadotropins (hCG) and equine chorionic gonadotropins (eCG) on in vitro gilt oocyte maturation and embryonic development, using frozen semen for fertilization. Methods: Two independent experiments (6 replicates each) were carried out to evaluate gilt oocyte maturation, and fertilization and embryonic development by using ovaries from a local abattoir. Totally, 712 oocytes were randomly distributed in four-well dishes to receive Novormon (eCG 5.0 IU), PG600 (eCG 5.0 IU and hCG 2.5 IU), Chorulon (hCG 5.0 IU), or no hormones. Oocytes were incubated with 5% CO2, 95% air and saturation humidity at 39 °C for 44 h. Maturation of the oocytes to metaphase II was assessed by using the aceto-orcein technique. In addition, 741 oocytes were used and randomly distributed in four-well dishes, and then oocyte maturation was carried out as mentioned, but matured oocytes were washed and placed in fertilization medium with frozen-thawed sperm. Gametes were co-incubated for 7 h, and then washed and placed in development medium, and incubated for further 7 days, at which time embryonic development was evaluated. Fertilization and embryo development media were not supplemented with the studied hormones. Results: Novormon (eCG) and PG600 (eCG+hCG) treatments significantly improved the percentages of metaphase II oocytes compared to the control group (P<0.05). Furthermore, a significant increase was also observed in the young blastocyst stage between the control group and the PG600 treatment group (P<0.05). Conclusions: Hormonal products Novormon (eCG) and PG600 (eCG+hCG) can obtain the highest percentages of in vitro maturation in gilt oocytes; however, this effect is not transferred to fertilization rates.