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New IUD For Suppressing Estrus In Mares

Owners of marish mares are always on the hunt for ways to suppress undesirable estrus-related behaviors in these horses. While many methods exist, some are more effective, practical, and even safe than others.

Author:Xander Oddity
Reviewer:Dr. Felix Chaosphere
Oct 23, 2023
Owners of marish mares are always on the hunt for ways to suppress undesirable estrus-related behaviors in these horses. While many methods exist, some are more effective, practical, and even safe than others. A researcher at the University of Massachusetts has devised a new drug-free approach for suppressing estrus in mares—one that could help manage performance mares and more.
Carlos Gradil, DVM, PhD, Dipl. ACT, professor in the school’s Department of Veterinary and Animal Sciences, in Amherst,and adjunct associate professor at Tufts University’s Cummings School of Veterinary Medicine, in North Grafton,described how to use the magnetic intrauterine device (IUD) and reported on its efficacy at the 2018 American Association of Equine Practitioners Convention,held December 1-5 in San Francisco, California.
Existing techniques for suppressing estrus in mares include administering progesterone or progestins (the estrous cycle’s dominant hormones), the hormone oxytocin, or a gonadotropin-releasing hormone vaccine (not approved for use in the United States); and inserting IUDsthat mimic pregnancy. Historically, IUDs such as marbles have been problematic, causing inflammation and infection, breaking, adhering to the endometrium (the uterine lining), and being unintentionally left in the mare for years—all of which can compromise her fertility.
So Gradil tested a new IUD he designed with safety in mind. Composed of three shatter-proof magnetic beads, the device self-assembles into a ring upon insertion with an applicator into the mare’s uterus. Veterinarians can place it into the mare during any stage of estrus, he said. Gradil described the device’s benefits, noting it:
  • Is drug and hormone-free;
  • Has a high retention rate;
  • Prolongs diestrus (the period between estrous cycles);
  • Is very convenient to insert and retrieve;
  • Does not affecting fertility; and
  • Is easy to visualize via ultrasound and identify with a metal detector.
In his study Gradil inserted the IUD into 15 mares in estrus and 14 control mares—regardless of stage of estrous cycle—and found that it extended their diestrus period by an average of 74 days. It was more effective in younger mares than older ones. He removed the devices after three to 18 months using a magnetic retriever designed specifically for the IUD. The mares had a 100% retention rate and 100% pregnancy rate afterward, he said.

Final Words

Gradil said this IUD can potentially help curb undesirable estrous behavior in performance mares, synchronize estrous cycles for embryo transfer, and control wild horse populations. He warned against using it in pregnant mares or those with existing uterine fluid or inflammation.
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Xander Oddity

Xander Oddity

Xander Oddity, an eccentric and intrepid news reporter, is a master of unearthing the strange and bizarre. With an insatiable curiosity for the unconventional, Xander ventures into the depths of the unknown, fearlessly pursuing stories that defy conventional explanation. Armed with a vast reservoir of knowledge and experience in the realm of conspiracies, Xander is a seasoned investigator of the extraordinary. Throughout his illustrious career, Xander has built a reputation for delving into the shadows of secrecy and unraveling the enigmatic. With an unyielding determination and an unwavering belief in the power of the bizarre, Xander strives to shed light on the unexplained and challenge the boundaries of conventional wisdom. In his pursuit of the truth, Xander continues to inspire others to question the world around them and embrace the unexpected.
Dr. Felix Chaosphere

Dr. Felix Chaosphere

Dr. Felix Chaosphere, a renowned and eccentric psychiatrist, is a master of unraveling the complexities of the human mind. With his wild and untamed hair, he embodies the essence of a brilliant but unconventional thinker. As a sexologist, he fearlessly delves into the depths of human desire and intimacy, unearthing hidden truths and challenging societal norms. Beyond his professional expertise, Dr. Chaosphere is also a celebrated author, renowned for his provocative and thought-provoking literary works. His written words mirror the enigmatic nature of his persona, inviting readers to explore the labyrinthine corridors of the human psyche. With his indomitable spirit and insatiable curiosity, Dr. Chaosphere continues to push boundaries, challenging society's preconceived notions and inspiring others to embrace their own inner tumult.
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