Embryo Transfer in Beef Cattle

Embryo transfer is a multi-step process that involves the production and collection of preimplantation embryos from genetically superior females (called donors) and the subsequent transfer of the harvested embryos into reproductively healthy females (called recipients) for the purpose of establishing pregnancies and producing live offspring. The first successful embryo transfer in mammals was performed with rabbits in 1890 (Heape, 1891), but it was more than 70 years later that the first successful embryo transfer in cattle was reported (Willett et al., 1951). Today, more than 3⁄4 million bovine preimplantation embryos are transferred each year throughout the world (Thibier, 2006). The embryo transfer process involves the following steps: 1. identification of genetically superior donor females 2. identification of reproductively healthy recipient females 3. synchronization of estrus in donor and recipient females 4. superovulation of donor females 5. detection of estrus in donor and recipient females 6. mating of superovulated donor females 7. recovery of preimplantation embryos from inseminated donor females 8. transfer of viable preimplantation embryos into recipient females If the transfer of preimplantation embryos from donor females can not be performed immediately after embryo harvest, it is also possible to cryopreserve (freeze) the embryos for transfer at a later date. As an alternative to the above process, it is also possible to produce preimplantation embryos in vitro (in the laboratory). The objective of this paper is to provide readers with an overview of embryo transfer, embryo cryopreservation, and in vitro embryo production in beef cattle.