Which insemination results in fertilization when several are performed before ovulation?

The research focused on determining which artificial insemination results in successful fertilization when horses are inseminated multiple times prior to ovulation. Their results suggest that the majority of successful fertilizations occur from inseminations conducted 2-4 days before ovulation, indicating that horse sperm can remain viable in the female reproductive tract for at least 2.6 days.

Study design and procedure

• The research involved horse females in their estrus (fertile) period which was spanned across 62 cycles.
• Artificial insemination was carried out at 48-hour intervals starting from when a follicle with a minimum size of 30 millimeters was spotted, continuing until ovulation.
• The number of inseminations was capped at three for each cycle.
• Three fertile male horses were utilized, with each one being used for one artificial insemination. No same male horse was used twice in the same cycle.
• The order of using the three male horses was altered each cycle to avoid bias.
• Embryos were gathered between the 10th and 12th days post-ovulation for paternity validation through DNA typing.

Results and Implications

• Out of 17 embryos resulting from two inseminations per cycle, 14 were a result of the insemination performed two to four days before ovulation.
• The remaining three embryos resulted from the insemination carried out zero to two days ahead of ovulation.
• In cases where three inseminations were carried out, the resulting embryos divided as per the insemination schedules as – 1 from insemination 4-6 days before ovulation, 2 from insemination 2-4 days before, and 3 from inseminations 0-2 days prior to ovulation.
• Thus 17 out of a total 23, or 74% of oocytes, were not fertilized by the insemination carried out 0-2 days before ovulation.
• The average interval from fertilization to ovulation was found to be around 2.6 days in the horses whose embryos were recovered and examined.
• The results highlight that horse sperm can stay viable in the female reproductive tract for at least 2.6 days.

Conclusion

• From the data, it’s clear that the majority of successful fertilizations are achieved through insemination that’s carried out 2-4 days before ovulation. This implies that those involved in horse breeding should aim for this timeframe to maximize successful fertilization rates.