Cooled-storage of equine semen does not induce major changes in sperm DNA methylation.

This study explored the influence of cooled storage on the DNA methylation of horse semen, and found no substantial changes. Also, sperm concentration didn’t appear to affect the longevity of cooled semen.

Research Objectives and Methodology

• The main objective of this research was to investigate whether cooled-storage changes the sperm DNA methylation level in horse semen.
• To investigate, the researchers collected semen from 10 healthy stallions and processed it for cooled-storage at 5°C.
• The samples were then divided into two final concentrations, 50 × 106 and 100 × 106 cells/mL.
• The researchers examined the semen for overall motility, progressive motility, membrane integrity, phosphatidylserine translocation (PST), mitochondrial membrane potential and chromatin condensation. These properties were assessed immediately after processing and at 24-hour intervals up to 72 hours of storage.
• Finally, DNA cytosine methylation was evaluated by conducting an ELISA (enzyme-linked immunosorbent assay) after DNA extraction and denaturation.

Findings and Conclusion

• The study’s findings show that DNA methylation in horse semen did not change over time, nor was it affected by the concentration of the semen.
• Few properties such as total motility, progressive motility, membrane integrity, PST, mitochondrial membrane potential, and chromatin condensation did change over storage time. However, there were no discernible differences between the two semen concentration groups. This indicates that a higher sperm concentration doesn’t necessarily affect the longevity of the semen.
• The conclusion of the research is that cooled storage of horse semen does not cause changes in sperm DNA cytosine methylation. Therefore, if the cooled semen is of high quality, having a concentration of 100 × 106 sperm/mL does not compromise its longevity.
• The researchers concluded that the superior fertility of cooled-stored compared to cryopreserved stallion semen might be partly due to the minimal changes in DNA integrity and methylation induced by cooled storage.