Could the Storage Time Post-collection Affect the Post-thaw Motility and Fertilizing Ability of Mediterranean Brown Trout Semen?

The aim of this study was to evaluate the effect of different cool storage time intervals between collection and semen freezing on both fresh and cryopreserved semen motility parameters and the post-thaw fertilizing ability of Mediterranean brown trout semen. The ejaculates were split into six aliquots and stored on ice for 1 to 6 hours, until freezing. Fresh and post-thawing sperm motility were evaluated by Computer-Assisted Sperm Analysis system, whilst the fertilizing ability was assessed by in vivo trials. In fresh semen, at 3 h of storage, a significant decrease of total motility, linear movement (STR, LIN) and beat cross frequency was recorded, whilst the amplitude of lateral displacement of the spermatozoon head underwent a significant increase. Velocity parameters (VCL, VAP and VSL) were not affected by the cold storage time, whilst the duration of sperm movement was significantly higher at 1h compared to the other times tested. Freezing procedure overall decreased almost all post-thaw sperm motility parameters, however no significant differences was observed over time, both in term of fast and linear movement. Cool storage time did not significantly affect the percentage of post-thaw eyed embryos. Our results showed that Mediterranean brown trout semen can be stored on ice even up to 6 hours before freezing, without decreasing its post-thawing quality and fertilizing ability.