Impact of using a fast-freezing technique and different thawing protocols on viability and fertility of frozen equine spermatozoa.

The study explores how the method of freezing and thawing impacts the quality and fertility of frozen horse sperm. It found that a rapid freezing technique along with a deep-horn insemination improves the viability and potential fertility of the sperm.

Methods and Materials

• The study analyzed ejaculates (sperm samples) from five stallions, making a total of 25 samples. These samples were frozen using either a conventional freezing technique or a rapid-freezing method.
• The frozen semen was then thawed using two different protocols: one at 37°C (98.6°F) for 30 seconds, and the other at 75°C (167°F) for 7 seconds.
• The viability of the thawed semen was evaluated based on progressive motility (ability to move forward), vigor (energy and strength), morphology (shape and development), and plasma membrane integrity.
• Twenty-five mares were inseminated with either 300 million (11 samples) or 150 million (14 samples) spermatozoa.

Results

• The study discovered that the rapid-freezing technique resulted in a greater number of vigorous and progressively motile spermatozoa, as compared to the conventional freezing method.
• Furthermore, the integrity of the plasma membrane (outer covering) of the spermatozoa was higher with the rapid-freezing method.
• Interestingly, the study found that the method of thawing did not seem to impact on the viability of the semen.
• The methods resulted in a pregnancy rate of 76% (19 out of 25) when the fast-freezing technique and deep-horn insemination were used. This rate did not vary significantly between the two different insemination doses used.

Conclusions

• The study concluded that using 150 million progressively motile spermatozoa per dose combined with deep-horn insemination maximizes the use of horse semen.
• Additionally, the fast-freezing technique, when compared to the conventional method, effectively preserves the viability and fertilizing capacity of the spermatozoa.
• This suggests that this new method could improve the fertility of frozen horse semen, and may have significant implications for the breeding and preservation of equine species.