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

Recovery of oocytes from ovaries collected at slaughter was carried ou t at three ambient temperatures (25 degrees, 30 degrees and 35 degrees C) to assess the effect on subsequent embryonic production in vitro. Oocytes recovered at each temperature were thereafter maintained at te mperatures greater than or equal to 35 degrees C as they were subjecte d to in vitro maturation, fertilization and culture (IVM/IVF/IVC). The oocytes and resulting embryos within each temperature group were subs equently evaluated for their rates of fertilization, cleavage and deve lopment to blastocysts, as well as for the number of cells/blastocyst. The results demonstrate that exposure of cumulus-oocyte-complexes (CO Cs) to temperatures below 35 degrees C during oocyte recovery is detri mental to optimal embryo production. Although the fertilization and cl eavage rates of oocytes recovered at temperatures below 35 degrees C w ere not significantly lower than that of the controls, the percentage of oocytes recovered at 35 degrees C that developed to the blastocyst stage following fertilization and culture (33.7%) was significantly gr eater than those from oocytes recovered at either 25 degrees C (22.4%) or 30 degrees C (19.5%). The mean numbers of blastomeres/embryo were significantly lower in embryos derived from oocytes collected at eithe r 25 degrees or 30 degrees compared with those collected at 35 degrees C. The results of this study suggest that exposure of COCs to tempera tures below 35 degrees C during oocyte recovery may significantly decr ease both the quantity and quality of embryos produced by in vitro met hods.