Artificial insemination and cryopreservation of boar semen: current state and problematics

Commercial artificial insemination with boar semen still prefers the usage of refrigerated semen up to 5 days over frozen-thawed, to date. This is because of the uneconomical properties of frozen-thawed boar semen, such as low motility, viability, fertility rates and the need for higher semen doses, because of the decreased quality after cryopreservation. Since boar semen is highly susceptive to cold shock damage, the invention of a successful cryopreservation method would be greatly beneficial for the swine industry. This review briefly focuses on the many factors that influence the quality of frozen-thawed boar semen, including the different compositions of extenders, comparison of commercial extenders, freezing and thawing methods (temperature and duration). It could be concluded from the present review that optimum freezing/thawing protocol for swine is not standardized, so far being the current status still considered poor-to-fair.