The present work summarizes the principles of cryoinjury and the relevance of
permeating and nonpermeating cryoprotective agents. Descriptions about sperm cryodamage are mainly focused on boar sperm, but reference to other mammalian species is
also made when relevant. Main cryoinjuries not only regard to sperm motility and
membrane integrity, but also to the degradation effect exerted by freeze-thawing on other
important components for sperm fertilizing ability, such as mRNAs. After delving into the
main differences between good and poor freezability boar ejaculates, those protein
markers predicting the sperm ability to sustain cryopreservation are also mentioned.
Moreover, factors that may influence sperm freezability, such as season, diet, breed, or
ejaculate fractions are discussed, together with the effects of different additives, like
seminal plasma and antioxidants. After briefly referring to the effects of long-term sperm
preservation in frozen state and the reproductive performance of frozen-thawed boar
sperm, this work speculates with new research horizons on the preservation of boar
sperm, such as vitrification and freeze-drying.