Hysteroscopic insemination of low numbers of flow sorted fresh and frozen/thawed stallion spermatozoa.

The research was conducted to study the impact of certain processes – flow cytometric sorting and freezing – on the fertility of stallion sperm. The study found no significant difference in pregnancy rates when using fresh or frozen sperm, whether it had been sorted or not. However, further research is suggested to verify if the fertility of flow sorted frozen sperm can be enhanced.

Objective and Methodology

• The experiment aimed at understanding the effects of flow cytometric sorting (a method used to sort or separate microscopic particles, in this case, spermatozoa) and freezing on stallion sperm fertility.
• The study employed a 2 x 2 factorial design. This means they used two types of sperm (fresh and frozen) and two treatments (sorted and unsorted) to examine the four combinations for their potential impact on fertility.
• The trial began with the synchronization of oestrus in 41 mares, inducing ovulation at specific times before insemination.
• The mares were then randomly assigned to one of the four treatment groups, fresh non-sorted, fresh flow sorted, frozen/thawed nonsorted, and frozen/thawed flow sorted spermatozoa.

Conducting the Experiment

• Semen was collected from two stallions and processed to delineate the effects of flow sorting and freezing spermatozoa.
• The flow sorting involved staining the collected sperm with a particular dye (Hoechst 33342) and segregating them into X and Y chromosome-bearing populations. This was done using an SX MoFlo sperm sorter.
• In treatments involving frozen spermatozoa, the sperm was frozen at specific concentrations.
• Regardless of the treatment, the concentration of the inseminated sperm was adjusted so that each insemination contained approximately five million motile spermatozoa.

Results and Conclusion

• Pregnancy in the mares was determined ultrasonographically (using ultrasound), 16 days post ovulation.
• The study’s findings showed no significant differences in the pregnancy rates among mares inseminated with the four different treatments of spermatozoa.
• The data did suggest, however, that the pregnancy rates were slightly lower following the insemination of frozen/thawed flow sorted spermatozoa. But this difference wasn’t statistically significant (P>0.1).
• The researchers concluded that more investigations are necessary with a larger sample of mares to determine if the fertility of flow sorted frozen/thawed spermatozoa can be improved.