Perspectives in porcine semen conservation (liquid and frozen)

In pigs, breeding primarily relies on Artificial Insemination (AI) with preserved semen. Maintaining sperm under proper conditions is thus vital for optimal reproductive performance. Currently, pig sperm can be preserved either in a liquid state at 15-20°C or 4-5°C, or cryopreserved, with most AI being conducted with liquid-stored semen at 15-20°C. This article reviews the state of the Assisted Reproductive Technology (ART) in preserving pig semen, focusing on the most recent advances. It describes the differences between conventional (15-20°C) and hypothermic (4-5°C) storage, and discusses the relevance of reducing the presence of antibiotics in semen extenders. The work also approaches sperm cryopreservation, including the effects of freezing and thawing on sperm function and survival, and on reproductive performance, and provides a general overview of the need to identify ejaculates with good cryotolerance. The effects of semen transport and the potential improvement from additives to preservation media are also discussed. The main take-home message is that AI with preserved sperm yields good reproductive performance, and that the perspectives for progress in the coming years should focus on reducing antibiotics and implementing methods that allow selecting ejaculates that withstand better liquid storage and/or cryopreservation.