Integrative assessment of gamete and embryo quality in porcine in vitro production: A comprehensive review

Despite significant progress in porcine in vitro embryo production (IVP), major challenges persist, particularly regarding the biological quality and developmental competence of gametes and embryos produced in vitro. The lack of standardised and objective evaluation criteria continues to limit the efficiency, reproducibility, and translational value of porcine assisted reproductive technologies (ART). This review provides a comprehensive synthesis of current methodologies used to assess oocyte, sperm, and embryo quality in pigs, integrating insights from other mammalian models to highlight common principles and species-specific challenges. Oocyte competence remains a key determinant of IVP success, yet its assessment is hindered by variable maturation efficiency, polyspermy, and inconsistent handling procedures. Emerging approaches such as advanced imaging, metabolomics, and single-cell transcriptomics show potential for non-invasive and dynamic evaluation of oocyte quality, but their routine implementation in routine practice requires further validation and inter-laboratory standardisation. Similarly, improving sperm assessment requires moving beyond traditional parameters such as motility and morphology toward integrative frameworks that incorporate molecular, biochemical, and imaging-based markers of functionality. The strong link between gamete quality and fertilisation outcomes highlights the need for harmonised protocols and validated species-specific biomarkers to ensure reproducibility across laboratories. At the embryonic level, the development of multiparametric, data-driven frameworks combining morphological, metabolic, and molecular indicators represents a pivotal step toward objective embryo quality assessment. Although artificial intelligence, high-throughput omics, and machine learning hold great promise, their adoption will depend on rigorous validation, cost-effectiveness, and standardisation to minimise operator-dependent variability and guarantee reproducibility. Ultimately, advancing porcine IVP will depend on integrating biological insights with technological innovations through non-invasive tools and robust quality control systems adapted to the species unique physiological characteristics. This convergence offers a pathway toward more efficient, reproducible, and predictive ART in pigs, with broad implications for animal breeding, genetic preservation, and translational biomedical research.