Relationships Among Follicular Fluid Estradiol-17.BETA. Concentration, Morphology of Cumulus-Oocyte Complex and Developmental Capacity of Individually Matured, Fertilized and Cultured Bovine Oocytes In Vitro.

The effects of follicular fluid estradiol-17β (FFE) concentration of individual follicle and the morphology of cumulus-oocyte complexes (COCs) on in vitro development of in vitro matured (IVM), in vitro fertilized (IVF) and in vitro cultured (IVC) bovine oocytes were investigated. All COCs were cultured individually throughout IVM to IVC. The types of cumulus cell layer were ≥4 and 2-3 layers, and the ooplasm types were homogeneous and heterogeneous (granulation). FFE in each follicle sized 2-8 mm in diameter was measured individually by enzyme immunoassay. Mean FFE concentration in the follicles containing oocytes with heterogeneous ooplasm was significantly lower (P<0.05) than that in follicles giving oocytes with homogeneous ooplasm (921 vs. 1493 pg/ml). The types of cumulus cell layer did not show significant difference in levels of FFE. However, regardless of the ooplasm types, developmental capacity was significantly higher (P<0.05) in the oocyte with ≥4 layers of cumulus cells than the oocytes with 2-3 layers of cumulus cells. The oocytes aspirated from follicles with less than 100 pg/ml FFE resulted in significantly low (P<0.05) proportions of cleavage, blastocyst and hatched blastocyst development as compared with those aspirated from follicles with higher FFE. The present results indicate that FFE levels affect oocyte quality and the in vitro developmental capacity of bovine oocytes cultured individually throughout IVM to IVC.