Characteristics of frozen epididymal spermatozoa from stallions that died 12 to 36 hours after colic surgery

Equine spermatozoa from the cauda epididymis were previously collected and frozen, and the fertility was assessed. Most studies were performed on healthy stallions that had undergone routine castration or on the epididymis collected at the abattoir, but there are no studies on the quality of epididymal semen in subjects which have died from colic or which underwent intensive care. The present study was designed to verify whether a severe illness could affect epididymal semen quality and freezability in the stallion. Therefore, epididymal semen characteristics during the freezing process in stallions which had died from colic and in healthy stallions submitted to elective castration were compared. Five stallions that had died from colic (ill stallions [ISs]) and seven stallions that had undergone elective castration (healthy stallions) were castrated, and cauda epididymis spermatozoa were collected and processed. Sperm quality was tested after collection, after washing procedures, at the end of the equilibration (5 °C for 75 minutes), and after freezing/thawing. Sperm quality was measured by objective motility characteristics, membrane and acrosome integrity, and mitochondrial activity. After collection, sperm in ISs showed low kinetic parameters (total motility: 17.3 ± 3%, progressive motility: 6 ± 1%, average path velocity: 57.4 ± 35.4 μm/s, straightness: 74.2%) compared with healthy stallions (total motility: 90.8 ± 3.7%, progressive motility: 70 ± 4%, average path velocity: 118.1 ± 12.6 μm/s, straightness: 82.4%) but demonstrated similar membrane and acrosome integrity (85 ± 2.8% vs. 87.6 ± 3.1%). Sperm kinetic parameters increased after washing procedures and cooling in ISs, reaching comparable values after equilibration (5 °C for 75 minutes) and freezing/thawing. The data reported in this study suggest that the quality of the equine epididymal spermatozoa cryopreserved in stallions that had died from colic was similar to that reported in epididymal sperm after elective castration and was also similar to the data reported in literature for cryopreserved equine semen.