Cryopreservation of Canine Semen: A Review

Cryopreservation of canine semen plays a vital role in modern dog breeding, genetic conservation, and assisted reproductive technologies. The ability to preserve spermatozoa for extended periods enables the exchange of valuable genetic material across geographical boundaries and facilitates breeding without the need to transport animals. However, the freezing–thawing process can induce significant damage to sperm cells due to cold shock, oxidative stress, and structural alterations in the sperm membrane. To address these challenges, several cryopreservation techniques, including the Uppsala, Norwegian, CERREC, and CERCA methods, have been developed to improve post-thaw sperm quality. The selection of suitable cryoprotectants and extenders is critical for protecting spermatozoa during freezing. Traditional extenders containing egg yolk and its derivatives, such as egg yolk plasma and low-density lipoproteins, are widely used because of their protective effects. More recently, alternative cryoprotectants like soybean lecithin and skim milk have gained attention. In addition, antioxidants and emerging biological strategies, including mesenchymal stem cells, show promise in mitigating oxidative damage and enhancing sperm viability during cryopreservation. This review summarizes the commonly used techniques for canine semen cryopreservation and highlights the role of various cryoprotectants and additives in maintaining sperm quality during long-term storage.