Sperm vitrification in horses and donkeys.

The research paper discusses a new method for sperm freezing, known as sperm vitrification, in horses and donkeys. The technique demonstrated similar or higher sperm motility when compared with conventional freezing methods, and showed potential fertility outcomes both in vitro and in vivo.

Techniques for Sperm Freezing

• The study addressed sperm vitrification, a freezing method that uses high cooling rates and non-permeable cryoprotectants agents. This method was applied to equids for the first time using the spheres technique, which involves directly dropping small volumes of sperm into liquid nitrogen.
• The second method incorporated for vitrification involved the use of 0.25 mL straws with outer covers. When compared to traditional freezing methods, the new technique resulted in similar or higher progressive motility in donkeys and horses respectively.
• The researchers also attempted vitrification of larger sperm volumes using 0.5 mL straws, but this approach resulted in poor sperm quality post the warming procedures.

Fertility Trials with Vitrified Sperm

• The researchers assessed fertility both in vitro (in the lab) and in vivo (in living organisms). For horses, the fertilising capacity of vitrified sperm was tested using heterologous in vitro fertilization (IVF). This method involves the fertilisation of an egg from a different species, in this case, a cow’s egg was used. The results showed that the vitrified sperm could penetrate the cattle oocytes (immature eggs) inducing pronuclear formation and hybrid embryo cleavage, indicating successful fertilization.
• In donkeys, in vivo fertility tests were performed on a small group of female donkeys, known as jennies. Although the pregnancy rates were similar for both artificially inseminated (AI) vitrified semen (22%) and frozen semen (10%), the inflammation in the uterus, a common side-effect of AI, resolved faster in the group inseminated with vitrified semen.

Conclusion

• This research concludes that sperm vitrification, particularly with the use of 0.25 mL straws with outer covers, can be optimized in horses and donkeys and presents a valid alternative to the traditional freezing methods.