Insemination results with slow-cooled stallion semen stored for approximately 40 hours.

The research studies the effects of different sperm extending methods and timing of insemination on the pregnancy rates in mares using slow-cooled, stored stallion semen. The results indicate a significant difference in pregnancy rates based on the extender used and the timing of insemination, particularly noting high success when insemination takes place both pre and post ovulation.

Research Methodology

• The semen of three different stallions was drawn and extended using two methods, the Kenney extender and a version of this extender that was modified.
• The extended semen was then cooled down gradually and stored for an average of 41 hours before it was used for insemination.
• Each insemination dose contained 1.5-2 billion spermatozoa in a volume of 40ml.
• In this study, 26 mares were inseminated over 30 cycles.

Findings

• The pregnancy success rate for sperm stored with the traditional Kenney extender method was 87% over 15 instances.
• When the semen was extended using the modified version of the Kenney extender, the success rate dropped to 60% over 15 instances, showing that the extending method significantly impacts the success rate.
• In the study, pregnancy rates were also impacted by the timing of the insemination in relation to ovulation.
• Mares inseminated exclusively before ovulation had a lower success rate at 58% over 19 instances. But the pregnancy rate increased to 100% with instances where inseminations occurred both before and after ovulation or only after ovulation.
• This indicates that post-ovulatory inseminations likely have an important role in ensuring pregnancies.

Conclusion

• The techniques used in this study, both in terms of semen extension and insemination timing, resulted in an overall pregnancy success rate of 73%, showing their effectiveness.
• This suggests that these methods would be useful for storing stallion semen for approximately two days before insemination.