Pregnancy rates of mares inseminated with semen cooled for 18 hours and then frozen.

The research studied the impact of cooling stallion semen for 18 hours at different temperatures and concentrations before freezing it, and the conclusion was that this process did not have a detrimental effect on the semen’s fertility or motility. The success of this process was measured by the pregnancy rates of the mares inseminated with the treated semen, which showed no significant difference compared to the control group.

Methodology and Findings

• The study was conducted in three stages or experiments.
• Experiment 1 evaluated the motility of sperm cooled for 18 hours at either 15 or 5 degrees Celsius and at two different concentrations – 400 or 200 x 10(6) sperm/mL – before being frozen. The findings showed that temperature, sperm concentration, and the interaction between these two factors had no effect on the total motility (TM) and progressive motility (PM) after cooling. Additionally, post-thaw TM and PM were found to be higher in control samples than in treated samples.
• Experiment 2 further explored the cooling procedures before freezing the semen, the sperm was either cooled to 5 degrees Celsius for 18 hours and then centrifuged, or it was centrifuged at room temperature and then cooled. The third group was centrifuged and frozen immediately as a control. Judging by post-thaw TM or PM, no significant differences were observed among these treatments.
• Experiment 3 tested the pregnancy rates of mares inseminated with semen that had been treated differently. In the first scenario, the semen was extended in a skim milk-egg yolk solution without glycerol, and then centrifuged, cooled to 5 degrees Celsius for 18 hours, and frozen. The control group was inseminated with semen that had been frozen directly, without the cooling period. The research found that the pregnancy rates did not significantly differ between mares that had received the cooled and frozen semen and those that had received the semen frozen directly without prior cooling.

Conclusion

• The research concluded that there was a viable procedure to cool stallion sperm for 18 hours before freezing, without leading to a decrease in fertility.
• This method was comparable to direct freezing in terms of both motility of the sperm and successful pregnancy rates in mares, indicating that it could offer a useful solution for transporting stallion sperm to specialized freezing facilities.