A Preliminary Report on Early Embryonic Development Following Oocyte Vitrification and In Vitro Fertilization in Sheep

Interest in oocyte cryopreservation has recently increased with the growing importance of in vitro embryo production, nuclear transfer, and gene banking (Gordon, 1997; Andrus et al., 2000). A relatively recent approach to achieve rapid freezing without the use of expensive freezing devices is called vitrification. Vitrification is defined as the physical process by which a highly concentrated solution of cryoprotectant solidifies during cooling without formation of ice crystals (Rall, 1987). Oocyte vitrification has been developed using mouse embryos (Rall et al., 1985). Recently, vitrification has also been attempted in the cow (Fuku et al., 1992; Vajta et al., 1998; Hurtt et al., 2000; Papis et al., 2000), pig (Isachenko et al., 1998), buffalo (Dhali, et al., 2000), and horse (Hurtt et al., 2000). The advantages of vitrification technology when compared with slow-rate freezing are the low price of equipment, the simplicity of the procedure, and the short time required (Palasz et al., 1996).