CRYOBIOLOGY OF INVITRO-DERIVED BOVINE EMBRYOS

The capability to produce bovine embryos from ovarian oocytes by in vitro methods of maturation, fertilization and culture has progressed very rapidly during the past few years. Efficient experimental and practical use of these in vitro-derived embryos requires that they be cryopreserved. Until recently, in vitro embryos were considered to be much more sensitive to freezing than in vivo embryos. Recent observations are beginning to reveal that high survival of cryopreserved in vitro embryos requires improvements in the techniques of maturation and culture, rather than simply changes in cryopreservation methods. The merging of these two aspects of mammalian embryology is yielding success; pregnancies have been produced and calves have been born as a result of the transfer of cryopreserved in vitro-derived embryos.