63 Use of noninvasive screening methods to estimate the developmental competence of bovine oocytes following in vitro fertilization

Recently trends in bovine embryo production have shifted, such that in vitro embryo production (IVEP) has exceeded in vivo-derived embryo production. Although the efficiency of IVEP has improved, it is estimated that only 20%–40% of oocytes will produce a transferable embryo. Thus, a large opportunity remains to optimize the selection criteria for oocytes that will produce a transferable blastocyst. Glucose and ketones are two sources of energy within the follicle, and they have been extensively investigated as factors contributing to oocyte competence. Our objective was to isolate follicular fluid after ovum pickup (OPU) and use glucose and ketone concentrations to predict blastocyst development. We hypothesized that glucose, ketones, or both would be determinants of blastocyst development. Cumulus–oocyte complexes (COCs; n = 2347) were collected from random and stimulated/synchronized estrous cycles as a part of a commercial embryo production facility (n = 76 OPU events). Follicular fluid collected from each donor (n = 76) was individually pooled and tested for glucose and ketone concentrations using a handheld monitoring device (ACON Laboratories). Following OPU, COCs were submitted to industry standard IVM, IVF, and culture. Owing to the commercial nature of the OPU facility, it was not possible to account for sire across IVF matings. Following IVF, putative zygotes were assessed for cleavage (3 days after IVF) and blastocyst development (7.5 days after IVF). Only donors with ≥50% cleavage (n = 44 donors, 1397 COCs) were included in the following analysis. Data were analyzed using SAS (version 9.3) in a PROC CORR model to determine correlations between follicular fluid glucose and ketone concentrations and different time points of embryo development. Concentrations of follicular fluid glucose ranged from 10.0 to 101.5 mg dL⁻¹ with an average of 39.5 mg dL⁻¹. Concentrations of follicular fluid ketones ranged from 0.0 to 0.6 mM with an average of 0.16 mM. There were positive associations (P < 0.05) between glucose and ketones (r = 0.78), number of oocytes matured and glucose (r = 0.60), number of oocytes matured and ketones (r = 0.49), number of oocytes fertilized and glucose (r = 0.65), percentage of zygotes cleaved and glucose (r = 0.65), and the percentage of zygotes cleaved and ketones (r = 0.52). There was no significant association between follicular fluid glucose or ketones and the percentage of developed blastocysts from matured oocytes (P > 0.10). In conclusion, follicular fluid glucose and ketones are positively associated with zygotic cleavage. The loss of associations after cleavage may in part be explained by the large variation of sires used for IVF. Further research is required to understand the metabolic or cellular relationships between follicular fluid glucose and ketone concentrations and oocyte developmental competence.