P-118: Developmental Competence of Ovine Embryos Derived from Frozen Oocytes Co-Cultured with Embryos Derived from Fresh Oocytes

Background: Currently, a limited number of studies have been done on the vitrification of small ruminant oocytes, especially in sheep, where poor developmental rates are obtained following immature and mature oocyte vitrification. Poor ovine oocyte cryopreservation could attribute to the damage to enzymes which has role in metabolic pathways. Therefore, production of cytokines and growth factors such as epidermal growth factor, platelet-derived growth factor, and interleukin 6, which are critical for subsequent embryo development, could negatively be affected in zygotes derive from vitrified oocytes. This study was aimed to evaluate the probable improvement of developmental competence of embryos derived from vitrified oocytes co-cultured with embryos derived from fresh oocytes. Materials and Methods: The in vitro matured oocytes were either vitrified or as fresh oocytes were in vitro fertilized and the presumptive zygotes were subjected to in vitro culture as 3 different groups; I. zygotes derived from fresh oocytes (fresh), II. co-culture of zygotes derived from fresh and vitrified oocytes (fresh-vitrified), III. zygotes derived from vitrified oocytes. The cleavage rate was then evaluated on Day 3 (Fertilization=Day 0). Results: The cleavage rate in embryos derived from vitrified oocytes in fresh-vitrified group (58.3 ± 5.3) was slightly higher than vitrified group (50.8 ± 3.5, p<0.05). Although, the corresponding rate in fresh group (80.9 ± 3.0, p<0.05) was significantly higher than other groups. Conclusion: Co-culturing of presumptive zygotes derived from vitrified oocytes with those derived from fresh oocytes could relatively improve the developmental competence of the former.