Oxidative Stress and Its Mitigation in Buffalo Sperm Cryopreservation - Mechanisms and Strategies

Abstract

Cryopreservation is integral to artificial insemination, facilitating the global dissemination of superior genetic material in livestock. However, the process induces oxidative stress (OS), significantly impairing sperm viability and fertility. Excessive reactive oxygen species (ROS) generated during freeze–thaw cycles cause lipid peroxidation, DNA damage, protein denaturation, and mitochondrial dysfunction, particularly in buffalo sperm, which are rich in polyunsaturated fatty acids and low in cholesterol. This results in compromised membrane integrity, reduced motility, and decreased fertilisation capacity. Strategies to mitigate OS include antioxidant supplementation, both enzymatic (e.g., catalase, SOD, GPx) and non-enzymatic (e.g., vitamins C and E, glutathione, trehalose), which enhance cryosurvivability and reduce ROS-induced damage. Additional interventions such as partial deoxygenation of extenders and removal of dead or damaged sperm via filtration, swim-up, density gradient separation, and antibody-conjugated nanoparticles further improve post-thaw semen quality. Despite significant progress, sperm cryopreservation still faces challenges due to reactive oxygen species (ROS) - related damage and variability in response among bulls, highlighting the need for continued research to refine cryopreservation techniques and improve reproductive outcomes in buffalo.