Effect of ambient temperatures during oocyte recovery on in vitro production of bovine embryos

Recovery of oocytes from ovaries collected at slaughter was carried out at three ambient temperatures (25°, 30°and 35°C) to assess the effect on subsequent embryonic production in vitro. Oocytes recovered at each temperature were thereafter maintained at temperatures ≤35°C as they were subjected to in vitro maturation, fertilization and culture (IVM/IVF/IVC). The oocytes and resulting embryos within each temperature group were subsequently evaluated for their rates of fertilization, cleavage and development to blastocysts, as well as for the number of cell/blastocyst. The results demonstrate that exposure of cumulus-oocyte-complexes (COCs) to temperatures below 35°C during oocyte recovery is detrimental to optimal embryo production. Although the fertilization and cleavage rates of oocytes recovered at temperatures below 35°C were not significantly lower than that of the controls, the percentage of oocytes recovered at 35°C that developed to the blastocyst stage following fertilization and culture (33.7%) was significantly greater than those from oocytes recovered at either 2.5°C (22.4%) or 30°C (19.5%). The mean numbers of blastomeres/embryo were significantly lower in embryos derived from oocytes collected at either 25°or 30°compared with those collected at 35°C. The results of this study suggest that exposure of COCs to temperatures below 35°C during oocyte recovery may significantly decrease both the quantity and quality of embryos produced by in vitro methods.