Cryopreservation of epididymal and ejaculated bull spermatozoa

Abstract

The present study was undertaken to assess viability of frozen–thawed bull semen collected from the bull’s ejaculate and cauda epididymis. A total of 30 ejaculates were collected from three bulls twice per week for 5 weeks (Control). Caudal epididymis were collected from slaughtered beef cattle of unknown origin from the local abattoir. Caudal epididymal sperm was recovered immediately after slaughtering (EP-0 h) and after cooling at 5°C for 24 h (EP-24). The epididymal and ejaculated samples were each pooled together before being extended with Triladyl. Diluted samples per treatment were loaded into a 0.25-mL French straw and cooled to 5°C in 4 h. Cooled straws were placed 4 cm above liquid nitrogen to freeze for 10 min. Frozen straws were immersed into LN2 and kept for 7 days at −196°C. Samples were analysed immediately after dilution and post-thawing using the computer aided sperm analysis for sperm motility rate, viability and acrosome defects. The highest sperm motility rates were observed with EJ-0 h before and after cryopreservation. However, the difference in sperm motility parameters between EP-0 h and EP-24 h evaluated before and after freezing was not significant (P > 0.05). Furthermore, no significant difference in live cells mean values was observed between the three samples on freezing (P > 0.05). In relation to spermatozoa acrosome defects, there was no significant difference observed among the three samples before and on freezing (P > 0.05). In conclusion, the results from the present study revealed that cooling of epididymides at 5°C for 24 h before the recovery of sperm cells was efficient in preserving epididymal sperm viability. However, ejaculated bull spermatozoa had higher sperm motility and viability rate than epididymal sperm.