Biomarkers of Oocyte Competence in Bovine In Vitro Embryo Production: Multi-omics Insights into Maturation, Cumulus–oocyte Communication, and Developmental Potential: A Review

Abstract

Oocyte developmental competence remains the principal bottleneck limiting the efficiency of in vitro embryo production in cattle, with blastocyst rates from abattoir-derived oocytes typically plateauing between thirty and forty per cent despite decades of refinement in culture systems. This review synthesises current understanding of the molecular determinants of bovine oocyte competence, drawing on transcriptomic, proteomic, metabolomic, and epigenomic evidence to construct an integrated picture of the pathways that separate a developmentally capable oocyte from one destined to arrest. Particular attention is given to the bidirectional communication between the oocyte and its surrounding cumulus cells, mediated through transzonal projections, gap junctions, and extracellular vesicles, as a central organising principle underlying competence acquisition. The composition of follicular fluid, mitochondrial DNA copy number and bioenergetic status, lipid and energy metabolism, cumulus cell transcriptional signatures, and epigenetic reprogramming of DNA methylation are each considered as candidate non-invasive or minimally invasive biomarkers with translational relevance to oocyte selection. The influence of environmental stressors, particularly heat stress and negative energy balance, is examined as a case study of how systemic physiology intersects with oocyte-intrinsic molecular pathways. The review further evaluates the extent to which multi-omics integration, including emerging artificial intelligence approaches to morphological assessment, has begun to yield practically useful predictors of developmental fate, as opposed to descriptive correlates, and identifies the methodological and biological gaps that continue to separate laboratory findings from field-deployable diagnostics. The synthesis presented here is intended to orient reproductive biologists, biotechnologists, and cattle breeding practitioners toward the biomarkers most likely to improve oocyte selection and in vitro embryo production efficiency in the coming decade.