Effects of two freezing methods and two cryopreservation media on post-thaw quality of stallion spermatozoa.

This research experiments with several combinations of freezing methods and cryopreservation media to discern the most effective ways of preserving equine sperm. The study uses data from 30 stallions, comparing techniques using a Styrofoam box filled with liquid nitrogen or an automatic freezer, along with two types of cryopreservation media. The results showed different measures depending on the approach used, indicating further research is needed to understand the fertility impact.

Introduction and Methods

• The study was primarily aimed at comparing the post-thaw characteristics of stallion semen using different freezing methods and preservation media. It was conducted in two different labs, with samples collected from 30 stallions.
• Two freezing methods were used for experiment: liquid nitrogen in a Styrofoam box and an automatic freezer. Regarding the preservation medium, they used extenders based on glycerol (Gent) and one combining methylformamide with glycerol (BotuCrio).
• The researchers used a mixed linear model for data analysis, considering laboratory conditions, preservation medium, freezing methods, and stallion as variables.

Results

• In terms of curvilinear velocity (VCL) or the speed of sperm movement, semen preserved with BotuCrio in the automatic freezer showed higher VCL compared to the ones preserved using Gent in the Styrofoam box.
• Semen frozen in BotuCrio in the Styrofoam box also had a higher VCL than semen preserved using Gent under the same condition.
• The study also evaluated the percentage of spermatozoa that maintained intact plasma membranes, an indicator of their viability. Sperm preserved in Gent in the Styrofoam box had slightly higher percentages compared to the ones preserved in BotuCrio in the same condition, but the difference was not significant.
• Another crucial feature to measure is the integrity of the acrosome membrane (part of sperm important for fertilization). The percentage was higher in sperm frozen in BotuCrio than the ones frozen in Gent.
• Studying mitochondrial membrane potential (energy status of cells), a higher percentage of semen preserved in Gent in the Styrofoam box had high mitochondrial potential than the ones preserved using BotuCrio under the same condition.

Conclusion

• The research shows noticeable differences in post-thaw characteristics of stallion sperm depending on the freezing method and preservation media used.
• While sperm stored in Gent seemed to retain better mitochondrial potential, those stored in BotuCrio showed higher VCL and better maintenance of the acrosome membrane.
• This study sets a foundation for further research. The authors recommend fertility studies to determine how these differences in cryopreservation methods and media could affect the fertility of inseminated mares.