We have promising proof-of-concept results with a small cohort of mares and would like to conduct further studies withadditional mares to address the safety and efficacy of this approach. This is a proof of concept project that addresses: a)potential harmful endocrine disruptors; and b) dangerous mare behavior patterns associated with estrus that put horse ridersand handlers at risk; and c) the hypothesis that current inadequacies in equine estrus control need to be revisited. Theobjectives of this study are to continue to test and perfect a new SIUD that would suppress the expression of estrus behavior inmares by extending the lifespan of corpora lutea. In addition, we will embed the devices with a i) progestogen, as a tool forestrus synchronization in embryo transfer programs, ii) copper, as a contraceptive and iii) test fertility in mares carrying a copper SIUD.