Vol. 9, Special Issue 4, Part B (2025)

In vitro embryo production (IVP) has become a cornerstone of modern dairy cattle breeding, with over 1.6 million IVP bovine embryos transferred worldwide in 2022. Despite its widespread adoption, IVP faces significant hurdles, including suboptimal embryo development efficiency and reduced post-transfer survival rates. This review emphasizes current research on interleukin-6 (IL-6), a multifunctional cytokine within the IL-6 family, and its role as an embryokine in enhancing bovine oocyte maturation, folliculogenesis, and early embryo development. IL-6 exerts its effects via the JAK/STAT3 signaling pathway, with studies demonstrating that its supplementation during in vitro maturation (IVM) and embryo culture increases inner cell mass (ICM) cell numbers and improves developmental competence. However, its influence on blastocyst formation and trophectoderm (TE) cell populations remains inconsistent. While elevated IL-6 levels in follicular fluid correlate with improved oocyte quality and higher implantation rates, excessive supplementation may impair maturation, potentially due to adequate endogenous IL-6 production. These findings underscore the context-specific nature of IL-6’s effects, highlighting its promise for optimizing IVP outcomes while revealing challenges, such as variable embryo responsiveness and unresolved questions about long-term developmental impacts. This review emphasizes the need for further investigation to refine IL-6 supplementation strategies, offering insights into its potential to advance bovine reproductive technologies and improve livestock productivity.