Potential of seminal plasma to improve the fertility of frozen-thawed boar spermatozoa

Artificial insemination (AI) is widely used for livestock breeding. Although sperm cryopreservation is the most efficient method for long-term storage, its use for porcine AI is marginal, because of its dramatic impact on sperm quality. While the removal of seminal plasma is a routine practice prior to porcine sperm cryopreservation, its beneficial role on sperm function has not been investigated in as much detail. In this context and despite seminal plasma being regarded as a mere vehicle of sperm, mounting evidence indicates that it could be positive for porcine sperm fertility. In effect, not only is seminal plasma able to interact with the female reproductive tract after mounting/insemination, but it has been demonstrated it modulates sperm function. For this reason, the composition of this fluid and its proteome have begun to be investigated in order to elucidate whether its components play any role in sperm function, fertility and cryotolerance. Previous research has demonstrated that seminal plasma may maintain the quality and fertilizing ability of frozen-thawed boar spermatozoa when added before or after cryopreservation. However, a large variety of results have been reported with both beneficial and detrimental effects, including studies in which no influence has been observed. This review examines the composition of porcine seminal plasma and summarizes the available published studies regarding seminal plasma supplementation to spermatozoa before or after freeze-thawing. The take-home message of this article is that clearing up the role of seminal plasma in sperm cryotolerance may increase the reproductive performance of frozen-thawed boar spermatozoa.