Production of viable bovine embryos by intracytoplasmic sperm injection of oocytes harvested from slaughtered old cows

Abstract: (1) Background: Intracytoplasmic sperm injection (ICSI) is currently used to increase fertilization success by avoiding several oocyte or sperm deficiencies that would normally prevent conception after in vivo fertilization or classical in vitro fertilization. This paper aimed at improving the in vitro fertilization protocol of bovine oocytes, harvested from old cows after slaughtering, using intracytoplasmic sperm injection; (2) Methods: Oocytes were harvested by puncture of follicles from ovaries obtained from slaughtered old cows, followed by aspiration. Out of the 127 cumulus-oocyte complexes that were harvested, 84 (66.14%) were declared suitable for cultivation, after morphological evaluation. Following oocyte maturation for 22 hours, 77 cumulus-oocyte complexes were morphologically intact and could undergo the steps required for intracytoplasmic injection of spermatozoa. Frozen-thawed bull semen was used for ICSI and the 77 fertilized oocytes were kept for 24 hours in an atmosphere enriched with 5% CO2.; (3) Results: Fertilized oocytes transformed into 46 zygotes (fertilization rate of 59.74%), while after 168 h of cultivation 38 transferable compact morulae or early blastocysts were obtained; (4) Conclusions: Intracytoplasmic sperm injection can represent a viable alternative to classical IVF, when oocytes or sperm with lower fertility are used.