PROSPECTIVE EVALUATION FOR RETRIEVABILITY AND EQUILIBRIUM DURATION ON BULL EPIDIDYMAL SPERM CRYOPRESERVATION

The cauda epididymis offers mature sperm for postmortem retrieval and cryopreservation, requiring effective retrieval techniques and equilibrium durations for successful cryopreservation. This study evaluated the impact of retrieval techniques and equilibration durations on cauda epididymal sperm quality from Bos indicus bulls. Testes from thirty-two bulls were collected at a slaughterhouse postmortem, transported at 5 °C, and sperm were retrieved 6 hours after slaughter using either retrograde flushing or the slicing float-up technique with an egg yolk citrate extender (fraction A). Samples were equilibrated for either 120 or 240 minutes at 5 °C; subsequently, they were diluted at 1:1 with fraction B (with 12% glycerol), loaded in 0.25 mL straws, and cryopreserved using liquid nitrogen vapour. Sperm motility and velocity traits were evaluated post-retrieval, post-equilibration, pre-freezing, and post-thaw with the aid of a computer-assisted sperm analysis system. Across all stages, the retrograde flushing technique significantly yielded sperm with higher total motility, progressive motility, and velocity indices (curvilinear velocity, straight line velocity, and time average velocity) in comparison to slicing float-up technique samples (P < 0.05). Meanwhile, samples equilibrated for 240 minutes had sperm with higher total motility, progressive motility, and velocity indices (curvilinear velocity, straight line velocity, and time average velocity across all stages in comparison to 120 minutes of equilibration (P < 0.05)). Thus, bull cauda epididymis sperm quality remained satisfactory when using the retrograde flushing retrieval technique and equilibration for 240 minutes.