Efficacy of a Y‐Design Silastic Elastomer Intrauterine Device as a Horse Contraceptive. Issue 6 (18th March 2021)

• Record Type: Journal Article
• Authors: Holyoak, G. Reed; Lyman, Candace C.; Wang, Shuodao; Germaine, Stephen S.; Anderson, Cory O.; Baldrighi, Julia M.; Vemula, Neha; Rezabek, Grant B.; Kane, Albert J.
• Is Part Of: Journal of wildlife management. Volume 85:Issue 6(2021)
• Page Start: 1169
• Page End: 1174
• Publication Date: 2021-03-18
• Subjects: contraception -- Equus ferus caballus -- feral horses -- fertility -- histopathology -- intrauterine device; Wildlife management -- Periodicals; Zoology -- Periodicals; 333.954
• DOI: 10.1002/jwmg.22027
• Languages: English
• ISSNs: 0022-541X

Abstract

ABSTRACT: To successfully manage population growth rates of free‐roaming horses ( Equus ferus caballus ), an effective, long‐acting contraceptive could be beneficial. We evaluated the efficacy and safety of an intrauterine device (IUD) in a breeding trial using seasonal pasture assemblages of 2 males individually pastured in large enclosures (~81 ha) each with 10 females per male. The study took place at a large animal research facility at Oklahoma State University in Stillwater, Oklahoma, USA. Specific objectives of the study were to evaluate the effectiveness of IUDs in preventing pregnancy over 20.5 months with return to fertility assessed over the subsequent 6 months and to evaluate potential effects of this IUD on ovarian function and uterine health (e.g., endometrial inflammation, infection, fibrosis). We developed a Y‐design IUD, made of silastic elastomer, and set the desired retention rate at 75%. After procurement of endometrial biopsies, we inserted IUDs into the uteri of 20 females and examined them via transrectal ultrasound every 2 weeks for detection of the device and assessment of uterine health. After 20.5 months we removed the remaining 15 IUDs, obtained a second endometrial biopsy for comparision, and returned the females to their respective males for continued breeding in efforts to assess uterine return to health as indicated by pregnancy rates. The Y‐design IUD met the 75% retention rate goal, with 100% contraception in females that retained the device; 12 of 20 treated females became pregnant (i.e. returned to fertility) after removal of the IUD. Based on these results, we conclude that the Y‐design IUD is a safe and effective device to control fertility in free‐roaming horses. © 2021 The Wildlife Society. Abstract : Our Y‐design silastic elastomer IUD maintained a 75% retention rate and prevented establishment of pregnancy over 20 months, but ovarian cyclicity was not altered; therefore, normal estrus and diestrus phases of the female's estrous cycle were maintained, with breeding activity occurring during estrus. Once we removed the IUDs 12 females became pregnant, conveying retention of fertility.