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The purpose of the study was to investigate the differences between motility, freezability and longevity of epididymal sperm, harvested from different segments of the cauda epididymidis [modificated from Fouchécourt et al. (2000)]. The sperm concentration and total amount of sperm in the different segments were determined as well.
Epididymal sperm was collected from 10 stallions (age 3 – 14 years) by retrograde flushing (E9) and slicing technique (E7, E8). Differences in sperm concentration and total amount of sperm between the 3 cauda segments were significant. The increase in sperm concentration and sperm amount from the distal to the proximal cauda region E7 to E9 was remarkable.
Sperm concentration was measured by counting chamber and NucleoCounter® SP-100. Both techniques showed high correlation between the results obtained.
Diluting the epididymal spermatozoa with Gent-extender led to an increase in motility compared with the motility after dilution with EquiPro™, but the motility of equine epididymal sperm showed a high individual variation and increased from segment E7 to E9. Comparing the subjective estimation and objective sperm analysis by CASA only the motility of the sperm harvested from E9 showed a positive correlation. The longevity of diluted epididymal sperm determined over 96 hours yielded a strong reduction of motility within the first 24 hours, but after 96 hours a small percentage of spermatozoa was still motile.
Cryopreservation was performed using four different techniques with or without previous cooling and with programmable freezer or floating rack. Freezing led to a remarkable reduction of motility and velocity of epididymal sperm from all segments, regardless of the freezing protocol. The freezability of sperm cells showed high individual variation as well. After cooled storage of the thawed sperm for 48 hours, the sperm motility was reduced. Regardless of the duration of storage and freezing protocol, sperm motility was always low. Spermatozoa, harvested from segment E7 and E8 were less motile and showed smaller velocity than those from segment E9. The longevity of thawed sperm from E7 and E8, frozen by freezing protocol SRS was reduced in comparison to the longevity of sperm frozen with the other freezing protocols. Collecting, processing, storage and freezing motile sperm from 3 different segments of the cauda epididymidis after castration of stallions is possible. Comparing 4 different freezing protocols, with or without previous cooling by programmable freezer and floating freeze rack, showed comparable results.