Alterations in the integrity of the acrosome and perinuclear theca in cryopreserved boar spermatozoa.

The objective of this study was to investigate the effect of cryopreservation on the integrity of the acrosome and the perinuclear theca substructure (PTS) of boar spermatozoa. Semen from six boars was used. The semen was collected, diluted, and sperm motility and concentration determined. Only ejaculates showing ≥70% motility were used in this study. Diluted semen was divided in two samples: one to be evaluated fresh, and other to be evaluated after freezing-thawing. Fresh and frozen-thawed semen samples were used to assess sperm viability and acrosome integrity by light microscopy using the triple staining technique and to evaluate the PTS integrity by electron microscopy. The frozen-thawed semen had a greater proportion (P<0.05) of acrosome reacted live spermatozoa, compared to the fresh semen. The freezing-thawing process reduced (P<0.05) the proportion of intact PTS spermatozoa. The value of acrosome reacted spermatozoa was correlated with the proportion of spermatozoa with altered or absent PTS, both in fresh (r=0.93; P<0.05) and in frozen-thawed (r=0.71; P<0.05) semen. In conclusion, cryopreserved boar semen showed some alterations in the integrity of the acrosome and the PTS that might be due to cryocapacitation.