Sperm transport and distribution in the mare.

The research investigated the distribution of sperm within the reproductive tract of fifty mares after insemination on different days of the oestrous cycle and found varying quantities of sperm in different areas, notably more in the right oviduct, and discovered that the stallion used influenced the number of sperm recovered from the oviducts.

Methodology

• Fifty mares were inseminated at varying stages of their oestrous cycle, which included Days 2, 4, 7, 11 or 17.
• A different stallion was used for each of the three trials to understand whether they had any impact on the distribution of spermatozoa.
• To observe the distribution of sperm, an analysis was conducted 12 hours after the insemination. This was carried out on subsequent days, labelled as Days 3, 5, 8, 12, and 18 in the study.

Findings

• The study found that only 0.06 to 2.21% of the inseminated spermatozoa were recovered from the reproductive tract of the mares. This shows that a small portion of the overall inseminated sperm is actually recovered from the tract.
• The researchers discovered differences in the sperm recovery based on the specific day of the oestrous cycle. More sperm was recovered from the cervix and uterus on Day 12 compared to Days 3, 5, 8 and 18.
• There was also a statistically significant difference in the number of sperm found in the oviducts on different days. More sperm was discovered in either or both oviducts on Days 5 and 8 than on Days 3, 12 and 18.
• An interesting discovery through this research was that there was a non-equal distribution of sperm in the oviducts. More sperm were found in the right oviduct than the left.
• The choice of stallion also influenced sperm recovery. The results showed that the quantity of sperm recovered from the oviducts varied significantly based on which stallion had been used for insemination.

Conclusion

• This study provides considerable insight into the distribution of sperm within the mare’s reproductive tract post-insemination. It highlights the disparities in sperm recovery depending on the day of the oestrous cycle, the location within the tract, and the stallion used.
• The findings could lead to more refined methods of equine artificial insemination, by taking into account the optimal days for insemination and acknowledging that sperm distribution is not uniform within the reproductive tract.
• The discovery of a stallion’s influence on sperm recovery suggests an area of further research into what specific factors about different stallions affects the quantity of their sperm recovered from the oviducts.