Effects of melatonin supplementation during in vitro maturation on developmental competence of domestic cat oocytes

Oxidative stress is a major factor that limits the efficiency of in vitro embryo production in felids. This study investigated the effects of melatonin supplementation during in vitro maturation on oocyte quality, cumulus cell apoptosis, embryo development, and integrin β5 expression in domestic cats. Supplementation with 0.01 μM melatonin significantly increased oocyte maturation and the cleavage rate compared with the control group (P < 0.05) and markedly reduced the proportions of caspase-3- and cleaved caspase-3-positive cumulus cells (P < 0.05), including under hydrogen peroxide treatment. Lower (0.001 μM) or higher (0.1 μM) melatonin concentrations did not have comparable benefits. Despite these improvements during early developmental stages, melatonin supplementation did not significantly enhance blastocyst formation, the total blastocyst cell number, or integrin β5 expression (P > 0.05). These findings indicate that melatonin exerts stage-specific benefits in feline reproduction, primarily supporting oocyte maturation and early embryonic development. Further optimisation of post-fertilisation culture conditions may be required to improve later developmental outcomes and integrin-related molecular features.