The interaction between seminal plasma, sperm, and endometrium in inter- and intra-species breeding in equids.

The study investigates the differences in post-breeding inflammation and fertility in mares when bred with donkeys or horses. It shows that mares bred with donkeys tend to show less inflammation and higher levels of certain anti-inflammatory elements compared to when they are bred with horses.

Study Objective and Methodology

• The research was designed to investigate the different responses of mares after being bred with either horses or donkeys. It tried to understand why mares often exhibit lower post-breeding inflammation and improved fertility when bred with donkeys, compared to when bred with horses.
• The researchers used various methods to measure and compare the levels of progesterone, pro- and anti-inflammatory cytokines such as IL1, IL1, IL4, IL6, CXCL8, IL10, in mares before and after being bred with horse or donkey semen.
• The study also analyzed the proteome and metabolome of both horse and donkey sperm and seminal plasma using LC-MS/MS, an analytical chemistry technique.

Findings

• The researchers found that mare cycles bred with horse semen had a greater concentration of progesterone than those cycles bred with donkey semen at 8 days post-ovulation.
• At 6 hours post-infusion, the researchers observed that the inflammatory response to donkey semen tended to be lower.
• They also found that donkey seminal plasma exhibited anti-inflammatory properties compared to horse semen and seminal plasma, as evidenced by the lesser presence of neutrophils in uterine cytology (a procedure used to examine cells from the uterus).
• Horse semen induced greater concentrations of IL6 and lesser concentrations of IL1, both of which are cytokines involved in inflammatory responses.
• The study also discovered that concentrations of PGE1, PGE3, and lactoferrin, which play a crucial role in immunomodulation, were significantly more abundant in donkey sperm and seminal plasma.

Conclusion

• The study concluded that breeding mares with donkey semen induces a similar post-breeding inflammation to horse semen. However, donkey seminal plasma is associated with a lower post-infusion inflammation response than other combinations soon after breeding.
• These observations could be linked to the anecdotal findings that mares bred with donkeys have less post-breeding inflammation and better fertility rates.