History and perspectives on bovine embryo transfer

ABSTRACT

On a worldwide basis, more than 750,000 embryos are produced annually from superovulated donors and more than 450,000 embryos are produced using in vitro techniques. Superovulation and embryo collection are done as frequentlu as every 30 days. Cryopreservation and direct transfer of frozen-thawed embryos results in pregnancy rates near that of fresh embryos. Since the zona pellucida-infact in vivo produced bovine embryo can be made specified pathogen-free by washing procedures, thousands of frozen embryos are marketed internationally on an annual basis. In vitro embryo production is used widely in countries like Brazil and Japan. Polymerase chain reaction (PCR) technology is currentlu being used for sexing embryos and this technology is beginning to be used for "embryo diagnostics" and "embryoi genomics". Sex-sorted bovine semen is also readily available and is being used increasingly, especially for in vitro embryo production.