Towards increasing stallion sperm longevity by storage at subzero temperatures in the absence of ice.

The research investigates a method to improve the longevity of stallion sperm by storing it at subzero temperatures without freezing it. It explores if sperm can be maintained in a supercooled state at -10°C, and addresses the challenges in achieving this.

Objective of the Research

• The primary purpose of this study is to explore the potential of increasing the longevity of stallion sperm by storing it at subzero temperatures, in the absence of freezing. The objective is to mitigate the damage and viability losses that occur during the freezing and thawing process of conventional cryopreservation.

Methodology

• In this research, stallion sperm was diluted in a stabilizing extender and then stored at -10°C in a supercooled state. The viability of the sperm was then compared with the viability of those stored at a higher temperature of 5°C.
• In order to depress the freezing point of the sample and inhibit surface-catalysed nucleation, 2% of Ficoll-400 was added to buffered saline and the sample was covered with mineral oil. This allowed the samples to be stored in a supercooled state.
• The addition of sperm to the specimens increased the incidence of sample freezing, however, about 40% of samples with 50×10 sperm mL remained non-frozen.
• To maintain the integrity of the sperm membrane during supercooled storage, the researchers added 100 mM sucrose.

Results and Findings

• The findings suggested that supercooled storage at -10°C maintained membrane intactness with the addition of 100 mM sucrose, although the preservation percentages were lower compared to those observed in refrigerated storage.
• The sperm motility appeared lost through supercooled storage but could be revived through substituting buffered saline with a milk-based extender as the base medium. Despite this, the percentages of membrane intact sperm were found to be lower.

Conclusion

• The research concludes that supercooled storage holds promise for semen preservation. However, it needs further optimization of the storage solution in order to preserve sperm motility and improve efficiency.