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Successful techniques of in vitro fertilization(IVF) are valuable for studying the process of fertilization and for developing economical procedures for gene and nuclear transfer in farm animals. To date, bovine IVF system has been developed with oocytes in vitro or vitro, but the resulting zygotes exhibit limited embryonic development after in vitro culture. Even though in vitro matured oocytes achieved high fertilization and cleavage rates, these embryos appear extremly low rate of pregnancies when transferred to synchronized recipients. Development of early bovine embryos in vitro is generally arrested at the 8-to 16-cell stage. However, recent use of somatic cells such as trophoblastic vesicle, granulosa and oviduct epithelial cell for co-culture with early bovine embryos has proven effective for development of embryos, matured and fertilized in vitro, past the in vitro cell blocks. These factors clearly indicate the value of the co-culture system in promoting development of bovine oocytes matured and fertilized in vitro to morula or blastocyst stage in vitro. In addition, co-culture system may beome a tool for evaluation of viability of ova that have been manipulated by procedures such as splitting, microinjection and nuclear transfer.
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