Diagnosis of the viability of early bovine embryos by fluorescence microscopy

Summary. A fluorescence microscopy technique using diacetylfluorescin (FDA) as a substrate has been tested for the evaluation of the viability of early bovine embryos. Five to 8-day old cattle embryos were incubated in PBS containing FDA concentrations of 1 : 400 000 or 1 : 800 000 for 3 to 5 min at room temperature. Embryos were then examined by reflected light fluorescence using a KP 490 and 520 barrier filter in a Zeiss Axiomat microscope. Their mitotic activity after 24 hrs culture in vitro was used to determine their viability. After 3 min of incubation in the FDA medium, 85 p. 100 of the brilliantly fluorescing embryos showed mitoses after culture. None of the non-fluorescing embryos developed in vitro. Some embryos (about 6 p. 100) contained both dead and living cells as determined using the FDA test ; a few of these differentially reactive embryos were viable, but most of them were not. Short-term incubation of embryos in FDA medium probably did not impair their development, and no teratogenic effects could be seen in 17 to 20-day old rabbit fetuses transferred after the FDA test.