In Vitro Production of Embryos from Vitrified Buffalo and Bovine Oocytes Following Intracytoplasmic Sperm Injection Technique
In vitro embryo production through in vitro fertilization (IVF) using cryopreserved oocytes results to poor outcome due to the hardening of the zona pellucida during freezing. More recent in vitro fertilization alternative is the intracytoplasmic sperm injection (ICSI), which allows for the mechanical injection of a single sperm into the ooplasm, maximizing the use of cryopreserved oocytes to produce embryos in vitro. A total of 96 ovaries from 48 swamp buffaloes with ages 5 to 10 yrs old, and 104 ovaries from 52 crossbred cattle with ages 3 to 8 yrs old were utilized in the study. Cryopreservation of buffalo and bovine oocytes was done using the Cryotop vitrification protocol. Vitrified-warmed oocytes were subjected to IVF or ICSI for production of embryos in vitro. The rates of blastocyst development were significantly higher with ICSI than IVF in both species implying that the procedure aided the penetration of sperm through the hardened zona pellucida of the vitrified oocytes without damage to the internal ooplasm. Buffalo oocytes survived cryopreservation better than those of cattle. The results suggest that ICSI can be used as an alternative to IVF for cryopreserved bovine and buffalo oocytes.
Key words: cryopreservation, intracytoplasmic sperm injection, oocytes, vitrification