Preservation of boar semen: An update

In the pork industry, artificial insemination and the storage of boar semen in liquid at 17°C are routinely applied to optimize the ejaculate and bring about rapid genetic changes that are reflected in the animal protein. Although the results are satisfactory, they are below what occurs with natural mating. It is currently possible to preserve boar semen with storage at 17°C and slow freezing, since to date there is only one study on vitrification, with negative results applicable only in the case of implementing an intracytoplasmic sperm injection. In both methods and due to the sensitivity of boar sperm to osmotic and temperature changes, there is a loss in the quality of the initial sample; however, slow freezing in boar semen has greater deleterious effects on the sample that are reflected in the pregnancy rates and number of live births. Therefore, only 1% of all inseminations are done with frozen semen. The aim of this review is to provide advances and results of studies conducted on the preservation of boar semen, delving more deeply into the critical points that each of the preservation techniques presents, including bacterial contamination, extender components, temperature, ice nucleation, use of additives in extenders and the main deleterious effects on sperm quality.