Methyl Gallate Enhances Post-Thaw Boar Sperm Quality by Alleviating Oxidative Stress and Preserving Mitochondrial Function

Cryopreservation is a crucial technique for the long-term preservation of swine genetic resources. However, its efficiency remains limited by cryo-induced oxidative stress, which compromises sperm membrane integrity, mitochondrial function, and fertilizing capacity. Methyl gallate (MG), a naturally occurring polyphenolic antioxidant, has demonstrated strong free radical scavenging and lipid peroxidation inhibitory properties. This study aimed to evaluate the effects of MG supplementation on sperm quality and fertilization capacity during boar semen cryopreservation. Semen samples were cryopreserved in extenders containing different concentrations of MG (0, 10, 20, 30, and 50 µM). Post-thaw sperm quality, oxidative status, mitochondrial activity, apoptosis-related markers, and in vitro fertilization (IVF) outcomes were comprehensively assessed. The results showed that supplementation with 20 µM MG significantly improved post-thaw motility, viability, membrane and acrosome integrity, mitochondrial membrane potential, ATP content, and antioxidant capacity, while decreasing reactive oxygen species (ROS) and malondialdehyde (MDA) levels and reducing apoptosis (<i>p</i> < 0.05). Moreover, the expression of the anti-apoptotic protein BCL-2 was upregulated, whereas that of the pro-apoptotic protein BAX was downregulated. Sperm cryopreserved with 20 µM MG also exhibited a significantly higher IVF cleavage rate compared with the control group (<i>p</i> < 0.05). In conclusion, MG supplementation effectively enhanced boar sperm cryosurvival by maintaining membrane stability, improving mitochondrial function, and mitigating oxidative stress during freezing and thawing. These findings suggest that MG is a promising antioxidant additive for improving the efficiency of boar semen cryopreservation systems.