Evaluation of bovine embryo biopsy techniques according to their ability to preserve embryo viability.

The purpose of this research was to evaluate three embryo biopsy techniques used for preimplantation genetic diagnosis (PGD) in cattle and to recommend the least invasive one for current use, especially when PGD is followed by embryo cryopreservation. Three hundred bovine embryos were biopsied by either one of the needle, aspiration or microblade method, and then checked for viability by freezing/thawing and transplantation to recipient cows. The number of pregnancies obtained after the transfer of biopsied frozen/thawed embryos was assessed 30 days later using ultrasounds. The results were significantly different between the three biopsy methods: the pregnancy rate was of 57% in cows that received embryos biopsied by needle, 43% in cows that received embryos biopsied by aspiration, and 31% in cows that received embryos biopsied by microblade. Choosing an adequate biopsy method is therefore of great importance in embryos that will undergo subsequent cryopreservation, as it significantly influences their viability after thawing.