EFFECT OF AMBIENT TEMPERATURES DURING OOCYTE RECOVERY ON IN VITRO PRODUCTION OF BOVINE EMBRYOS

Abstract 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 cells/blastocyst. The results demonstrate that exposure of cumulus-ocyte-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 25 °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.