Reactive Oxygen Species‐Induced Damage in Cryopreserved Bovine Sperm: Mitigation Strategies

BACKGROUND: The importance of sperm cryopreservation in cattle production is that it enables the flow of genetic variation and the speedy distribution of genetically superior bulls. Nevertheless, there are still considerable technological gaps because the quality of post-thaw sperm is always poor and differs significantly across breeding bulls. OBJECTIVES: The aim of this review was to investigate the origin of reactive oxygen species (ROS) generation in the process of bovine sperm cryopreservation, discuss the effects of ROS-induced injury, and present the current knowledge of the measures the researcher can take to alleviate the impact of oxidative stress. METHODS: A thorough literature review was made by searching the relevant scientific databases with the keywords: bull sperm cryopreservation, ROS, oxidative stress, antioxidants, non-antioxidants approaches and post-thaw sperm quality. RESULTS: Freeze-thaw stress causes extreme cellular and molecular stress and ROS overproduction, which is one of the major causes of sperm damage. The main causes of ROS production are changes in osmotic pressure, the presence of ice crystals, mitochondrial dysfunction and oxidative burst. In turn, excessive production of ROS causes lipid peroxidation of the plasma membrane, oxidation of proteins, fragmentation of the DNA and dysfunction of the mitochondria, which eventually decreases the sperm motility, viability and fertilization capacity. Enzymatic and non-enzymatic antioxidants, plant extract, nanoparticles, mitochondria-targeted antioxidants and non-antioxidants approaches have proven to be effective in curbing oxidative damage. CONCLUSION: Prevention of oxidative imbalance in cryopreservation is an important factor that can increase the quality of post-thaw sperm and increase the success of artificial insemination and in vitro fertilization programmes in cattle.