Melatonin Improves Bovine Embryo Production and Quality via Antioxidant, Metabolic, and Epigenetic Pathways

This study aimed to evaluate the effects of melatonin supplementation during bovine in vitro embryo production (IVEP) on embryonic development and quality, oxidative stress, lipid metabolism, mitochondrial activity, gene expression, DNA methylation patterns, and cryotolerance. Four treatments were tested: control (without melatonin), melatonin at maturation (IVM + Mlt), culture (IVC + Mlt), and both treatments (IMV/IVC + Mlt). Melatonin significantly improved blastocyst rate and developmental kinetics on D7, reduced ROS and intracellular lipid levels, and increased mitochondrial activity. The most significant effects were observed in the IVC + Mlt group. Melatonin modulated antioxidant (SOD1, Cat, and GSS) and epigenetic (TET1, TET3, and DNMT3A) genes, and although it did not alter lipid gene expression, it reduced lipid content. Methylation analysis showed hypomethylation patterns in repetitive regions (Satellite I and LINE-1), which were even more pronounced in the melatonin-treated groups. However, no significant differences were observed between treatments in terms of cryotolerance or apoptosis rates. These findings suggest that melatonin exerts positive multifactorial effects, regardless of the supplementation stage. In particular, its addition during the IVC phase appears to provide greater benefits to embryos by improving their quality.