Advances in synchronization and superstimulation for OPU/IVEP: optimizing oocyte quantity and quality

The sustained expansion of in vitro embryo production (IVEP) in cattle necessitates ongoing advancements in IVEP methodologies. The success of IVEP largely depends on the quantity and quality (i.e. developmental competence) of oocytes retrieved after ovum pick-up (OPU). The fundamental role of the ovarian follicle in the development of the oocyte highlights the importance of considering the ovarian physiology during development of OPU/IVEP methodologies. Oocyte quantity is largely influenced by ovarian phenotype determined through antral follicle count (AFC) or circulating anti-Müllerian hormone (AMH). In addition, substantial evidence indicates that follicle size and status can affect OPU/IVEP outcomes such that promoting the presence of medium to large sized dominant-like follicles can enhance oocyte developmental competence and thus embryo production. Ovarian superstimulation, using follicle-stimulating hormone (FSH), allows optimization of follicle development and oocyte developmental competence resulting in greater IVEP efficacy. The present review examines various aspects of FSH administration, providing an update of ovarian superstimulation methodologies and their implementation in OPU/IVEP systems. Additionally, the potential development of targeted ovarian superstimulation approaches that consider the marked physiological differences among individuals with varying AFC/AMH phenotypes is explored with the goal of further enhancing IVEP efficacy.