Viability of bull epididymal spermatozoa recovered 24 hours post-mortem and diluted with Triladyl® and modified Ham’s F10

Context The unexpected loss of economically important animals or the inability of the male to mate can result in significant losses in genetic resources, impacting both short-term economic value and long-term population sustainability and resilience. Aim This study aimed to evaluate viability of bull spermatozoa recovered post-mortem from epididymides stored at 5°C for 24 h, compared with epididymal spermatozoa collected immediately after bull slaughter, diluted with Triladyl® (EPT) and modified Ham’s F10 (EPH). Ejaculated spermatozoa (EJ) were used as a control. Methods Cauda epididymal spermatozoa samples were recovered immediately (EPT0 and EPH0) and 24 h post-mortem (EPT24 and EPH24). Spermatozoa samples were separately pooled before dilution with Triladyl® or modified Ham’s F10 and chilled at 5°C for 120 h. Key results Epididymal spermatozoa diluted with Triladyl® showed higher total motility rates (P < 0.01) than those diluted with modified Ham’s F10. The highest spermatozoa motility rates were, however, observed with EJ (P < 0.01). Furthermore, EPT0 and EPH0 showed higher spermatozoa motility and kinematic rates (P < 0.01) than EPT24 and EPH24, with no significant difference in total motility rates observed between EPH0 and EPT24. The samples EJ and EPT0 displayed no significant decrease in cell viability during the 120 h storage period, maintaining the highest percentages of live cells. Conversely, a significant decline in cell viability was observed after 72 h for the samples EPH0, EPH24, and EPT24, with EPH24 showing the lowest percentage of viable cells. Additionally, < 10% acrosome defects were observed across all the samples. Conclusion The findings from this study demonstrated that refrigeration of epididymides at 5°C for 24 h before spermatozoa collection effectively maintained spermatozoa viability until 72 h when Triladyl® extender was used. Implications These results suggest that storing epididymides at 5°C for 24 h can be a viable method for preserving bull spermatozoa, which could help mitigate the loss of genetic resources and support both economic and population sustainability.