Improved cryosurvival of stallion spermatozoa after colloid centrifugation is independent of the addition of seminal plasma.

This study investigates how the addition of seminal plasma, prior to cryopreservation, influences the survivability of stallion sperm. Researchers found no additional benefit when seminal plasma, from either good or bad freezer stallions, was added to the spermatozoa selected by single layer centrifugation before freezing.

Research Method

• The semen from 12 stallions was collected and divided up. Five milliliters was set aside as a control, and the rest was processed to remove seminal plasma through a method known as single layer centrifugation (SLC).
• The processed semen was then divided into three subsets: One that didn’t have seminal plasma added back in (SLC), one that had seminal plasma from “good freezer” stallions added (SLC-GF), and one that had seminal plasma from “bad freezer” stallions added (SLC-BF).
• These samples were then frozen and later thawed. After this process, sperm quality indicators such as chromatin integrity, mitochondrial membrane potential (MMP), membrane integrity, reactivity to oxygen species, and sperm kinematics were evaluated.

Key Findings

• Comparing to the control group, the SLC samples (without added seminal plasma) showed a reduced percentage of DNA fragmentation Index (%DFI). This result suggests that sperm quality is increased by single layer centrifugation.
• The SLC group displayed a higher proportion of spermatozoa with high MMP and lower proportion with low MMP compared to the other groups.
• The SLC sample also displayed lower hydrogen peroxide content, an indicator of less reactive oxygen species which tends to lower survival rates.
• No significant differences were observed in sperm kinematics (motion and behavior).
• No beneficial effect was observed when seminal plasma from good or bad freezer stallions was added to spermatozoa before cryopreservation.

Conclusion

• The research concluded that selection of spermatozoa by SLC prior to cryopreservation has a beneficial effect on post-thaw sperm quality. This improvement does not depend on the addition of seminal plasma from either good or bad freezer stallions. That is, the addition of seminal plasma does not confer any additional benefit for the cryosurvival of stallion spermatozoa.