Abstract

Transmission electronic microscopy was used to test the efficiency of the classification criteria for Bos taurus embryos using conventional stereoscopic microscopy, since the criteria used for Bos indicus has proved inaccurate with the latter method. Embryos were collected from Holstein heifers 7 days after artificial insemination and classified according to the criteria established by the International Embryo Transfer Society (IETS). Ten embryos were sorted in each quality group (good, fair, and poor), processed and fine sections obtained for evaluation under electron microscope. Results showed that embryos classified as good using stereoscopic microscopy increased from 33 to 47% when evaluated by transmission electronic microscopy, while the fair embryos decreased from 33 to 20% and the poor embryos did not change. Likewise, using the Kappa Cohen’s test the rate of correlation between the evaluation methods this was found to be moderate. These findings show that the greatest variation between the two methods used is within the embryos classified as fair.  In conclusion, the classification criteria for Bos taurus proposed by the IETS is accurate for Bos taurus type embryos and those classified as fair should be considered for freezing, as their cellular structure show capacity to resist cryopreservation.

Key words: Bos taurus, embryonic quality, morphological evaluation, electron microscopy, stereoscopic microscopy.