MORPHOLOGY AND BIOCHEMISTRY OF IN-VITRO PRODUCED BOVINE EMBRYOS - IMPLICATIONS FOR THEIR CRYOPRESERVATION

Examination of some ultrastructural and physiological characteristics of in-vitro produced bovine embryos may help to explain why such embry os are more sensitive to freezing than their in-vivo derived counterpa rts. Improvement of embryo survival after freezing can be achieved by changing the conditions of their culture, selection of embryos based o n the kinetics of their development, and changing 'standard' freezing procedures, Cryopreservation of embryos by vitrification, in particula r, seems to yield higher survival than conventional slow freezing. Fur ther development of protocols requires additional embryo transfer stud ies to ensure that the ability of thawed embryos to develop normally i n vivo correlates strongly with in-vitro survival assays.