Cryopreservation of Andalusian donkey (Equus asinus) spermatozoa: Use of alternative energy sources in the freezing extender affects post-thaw sperm motility patterns but not DNA stability.

This study explores the effect of different sugars and Equex paste on the quality of cryopreserved Andalusian donkey sperm, finding that different sugars affect sperm motility and membrane integrity, with sorbitol potentially offering quality improvements. However, Equex paste seemingly shows no beneficial effects, suggesting its use may negatively impact sperm viability post-thaw.

Study Context and Objectives

• This study was centered on the cryopreservation of Andalusian donkey sperm, a process which involves freezing and storing at very low temperatures to maintain viability.
• The researchers aimed to investigate the effect of using three distinct sugars – glucose, fructose, and sorbitol – in the freezing extender, a substance used to preserve sperm during the freezing process. Apart from sugars, Equex paste was also used.

Methodology

• Sperm samples were collected from six fertile Andalusian donkeys, with two ejaculates pooled from each animal, resulting in a total of eighteen samples.
• The ejaculation samples were frozen using extenders containing one of the three sugars, either with or without the addition of Equex paste.
• Multiple aspects of sperm quality were then assessed both pre and post the freezing-thawing process. These aspects included sperm motility, morphology, integrity of the plasma membrane and DNA, and acrosome integrity.

Results

• Use of sorbitol in the freezing extender improved total and progressive sperm motility more effectively than other sugars. However, it was less effective for other sperm motility measures.
• By contrast, fructose reduced most Computer Assisted Sperm Analysis (CASA) variables, which are indicators of sperm quality.
• Equex paste showed no beneficial effects on sperm quality variables.
• Among the sugars, glucose was best at maintaining sperm morphology.
• Addition of fructose and Equex paste in the freezing extender decreased plasma membrane integrity as compared to glucose.
• No differences were recorded between treatments for acrosome and DNA integrity.

Conclusions and Implications

• The research findings suggest that the choice of sugar sources in the freezing extender can affect the post-thaw quality of cryopreserved donkey sperm.
• Sorbitol seemed to present as an effective alternative in improving sperm quality post-thaw.
• Equex paste was found to have no beneficial effect on sperm quality, potentially negatively impacting post-thaw sperm viability. This suggests the need for reconsideration of its use in cryopreservation.