Pregnancies produced from fertile and infertile stallions by intracytoplasmic sperm injection (ICSI) of single frozen-thawed spermatozoa into in vivo matured mare oocytes.

The research demonstrates the successful use of intracytoplasmic sperm injection (ICSI) involving single frozen-thawed sperm cells from both fertile and infertile stallions to facilitate in vitro fertilization of equine oocytes, which were then implanted into mares and resulted in successful pregnancies in some cases.

Research Methodology

• The research focused on the application of intracytoplasmic sperm injection (ICSI) to facilitate in vitro fertilization of horse (equine) oocytes.
• The oocytes were harvested from mature follicles 39 hours after injection with a GnRH analogue. These oocytes were then transported a distance of 190 km at a temperature of 39 degrees Celsius.
• Semen from both a fertile and an infertile stallion was collected, frozen, and prepared for the injection process.
• The successfully injected oocytes were then surgically implanted into the ampulla of the fallopian tube within two time frames: either 4-8 hours after semen injection or after a culture period of 24-48 hours.

Research Findings

• Out of 26 oocytes treated via ICSI, three oocytes fragmented post-injection, and eight were returned for immediate transfer to recipient mares.
• Among the 15 cultured oocytes, eight exhibited two polar bodies and cleaved into two-cell embryos 24 hours after the injection.
• Pregnancies were detected on days 12-14 after transfer in four out of sixteen recipients that had either received transferred embryos or freshly injected oocytes.
• Out of the four pregnancies, two did not progress beyond day 30 while the other two mares gave birth to foals.
• No significant differences were observed in the establishment of pregnancies from oocytes injected with the frozen-thawed spermatozoa of the fertile or infertile stallion.

Research Implications

• The results of this research demonstrate the potential effectiveness of ICSI in facilitating in vitro fertilization of equine oocytes using frozen-thawed sperm cells from both fertile and infertile stallions.
• This suggests that this method could hold significant promise for equine breeding practices, potentially enhancing fertility outcome, especially in cases involving infertile stallions.
• However, further research and larger sample sizes would be necessary to fully validate these findings and to understand any potential long-term implications of this approach.