Effect of cooling rate on sperm quality of cryopreserved Andalusian donkey spermatozoa.

This research investigates how different rates of cooling impact the quality of cryopreserved Andalusian donkey sperm. It found that a controlled cooling rate prior to freezing improves sperm quality.

Study Methodology

• The study used eighteen ejaculates from six adult Andalusian donkeys. Three ejaculates were extracted from each specimen.
• These samples were collected using an artificial vagina and then pooled, combing two ejaculates per pool. The mixed samples were then broken down into three separate groups to be treated with three varying cryopreservation procedures.

Cryopreservation Protocols

• The first protocol, P1, was a conventional slow freezing method. This involved pre-cooling the semen in an Equitainer for two hours before freezing in liquid nitrogen vapour.
• Protocol P2 involved a controlled pre-freezing cooling rate. The semen was pre-cooled at a contrived rate for 73 minutes before freezing in liquid nitrogen vapour.
• The third protocol, P3, was a rapid freezing method. This process involved immediately freezing the semen in liquid nitrogen vapour.

Post-Thawing Analysis

• Once frozen, the semen was thawed at 37 degrees Celsius for 30 seconds.
• The samples were then evaluated for various factors including motility, morphology, plasma membrane integrity, acrosome integrity, and DNA integrity.
• Significant differences were found between all sperm parameters evaluated among the three protocols, aside from DNA integrity.

Findings

• The study concluded that semen samples frozen using the controlled pre-freezing cooling rate protocol, P2, demonstrated higher values for sperm motility, morphology, sperm membrane integrity, and acrosome integrity.
• The rapid freezing method, P3, reduced sperm motility significantly and also increased the percentage of spermatozoa with damaged plasma membranes.
• The controlled cooling rate method, P2, was found to be the best protocol for cryopreserving Andalusian donkey semen.

Conclusion

• This research suggests that the sperm of the Andalusian donkey is greatly sensitive to the cooling rate used before freezing and that Andalusian donkey semen can be effectively cryopreserved using controlled cooling rates combined with freezing in liquid nitrogen vapour.