Modification of O-ring intrauterine devices (IUDs) in mares: Contraception without estrus suppression.

This research examines the effectiveness of different intrauterine devices (IUDs) in preventing pregnancy in horses. The findings can be used to address overpopulation issues in free-roaming horses on the US western open range lands.

Objective of the Research

• The main goal of the study was to find an affordable and humane method to control the population of free-roaming horses in the western areas of the US through preventing pregnancy.

Methodology

• The researchers conducted a series of studies using O-ring IUDs, which are previously described contraceptive devices placed inside the uterus of the horses.
• The effectiveness of these IUDs was evaluated in terms of pregnancy prevention and retention rate, the latter referring to the ability of the IUDs to stay in place within the uterus.
• The O-ring IUDs were also compared to Y-design IUDs, a more recent design of the same device.

Results

• It was found that while O-ring IUDs were able to prevent pregnancy, their retention rate was less than 50%, making their effectiveness questionable.
• On the other hand, Y-design IUDs demonstrated much higher retention rates, indicating they might be more suitable for use in free-roaming horses.
• The researchers also found that while the IUDs were able to prevent pregnancy, they didn’t suppress estrus in the majority of mares, meaning the females continued to ovulate and engage in mating behaviours.
• Multiple small ovarian follicles were observed in some mares with IUDs, suggesting that relying upon IUDs for estrus suppression may not yield effective results.

Conclusion

• The study concludes that the Y-design IUDs may prove beneficial for addressing overpopulation issues in free-roaming horses in the western parts of the US. However, the use of IUDs may not be successful as a means of suppressing estrus in mares.