Equine Sperm Function and Cryopreservation Techniques

Equine spermatozoa are highly specialised cells whose primary function is to deliver paternal genetic material to the oocyte. Structurally, they comprise a head containing the nucleus and acrosome, a midpiece enriched with mitochondria to power motility, and a tail providing propulsion. In vivo, sperm transit through the mare’s reproductive tract encounters varying pH and ionic environments, with seminal plasma components modulating capacitation, membrane stabilisation and protection against oxidative damage. Cryopreservation of sperm offers a means to store genetic resources, facilitate international trade of valuable stallions and support conservation of rare equid breeds. Conventional protocols involve dilution in a cryoprotectant extender, controlled-rate cooling, rapid freezing—often in vapour over liquid nitrogen—and thawing under precise conditions. Despite advances, freezing and thawing impose osmotic stress, lipid phase transitions in membranes and generation of reactive oxygen species, all of which can impair motility, membrane integrity and fertilising capacity. Recent efforts have focused on optimiser extender composition, antioxidant supplementation and biomarkers of post-thaw viability, with an aim to enhance both practical utility and global genetic diversity in equine populations.

Research from Nature Portfolio

Recent studies have examined the oxidative profile of donkey seminal plasma in relation to sperm quality. Investigations of free radical scavenging activity, total antioxidant capacity and nitrate/nitrite levels revealed strong correlations with sperm concentration, production and kinetic parameters. In parallel, protease inhibitor activity was shown to align closely with sperm output but not with motility indices. These findings indicate that assessment of specific oxidative and protease markers in seminal plasma may serve as reliable indicators of semen quality prior to cryopreservation, offering a rapid tool to predict post-thaw performance in donkey and potentially other equid species.

Equine Sperm Function and Cryopreservation Techniques publication trend

The graph below shows the total number of articles in equine sperm function and cryopreservation techniques across all publications each year (not limited to Nature Index journals).

Technical terms

Seminal plasma: Fluid portion of ejaculate containing proteins, enzymes and antioxidants that support sperm function.

Cryopreservation: Process of preserving cells by cooling to sub-zero temperatures, typically using liquid nitrogen.

Cryotolerance (freezability): Ability of sperm to withstand freezing and thawing without significant loss of function.

Reactive oxygen species (ROS): Chemically reactive molecules derived from oxygen that can damage cellular components.

Antioxidant enzymes: Proteins such as superoxide dismutase and glutathione peroxidase that neutralise ROS.

Motility: Capacity of sperm to move actively and progress effectively, often assessed by computer-aided systems.

Plasma membrane integrity: Measure of the sperm cell membrane’s intactness, essential for fertilising ability.

References

1. Oxidative profile and protease regulator potential to predict sperm functionality in donkey (Equus asinus). Scientific Reports (2021).
2. Impact of Seminal Plasma Antioxidants on Donkey Sperm Cryotolerance. Antioxidants (2022).
3. Specific Activity of Superoxide Dismutase in Stallion Seminal Plasma Is Related to Sperm Cryotolerance. Antioxidants (2019).