Investigation Into the Safety and Clinical Effects of a New Progesterone Releasing Intra-vaginal Device (PRID®Delta) in Mares

Abstract

The present study evaluated a novel intrauterine device for its effect on estrus suppression. The self-assembling intrauterine device (Upod) consists of three 12 mm × 26 mm elliptically shaped units each with a magnetic core and coated with a polymer (total weight 22.5 g). Each magnetic unit is inserted independently from the other. Once inside the uterus, these magnetic elliptical units self-assemble and adapt the lower energy “ring” conformation. In mares, the devices can be inserted at any stage of the estrous cycle without the need for multiple exams. Shatter-proof grade material is used to assure safety for long-term use. The Upod is inserted and retrieved using an applicator and magnetic retriever. In experiment 1, Upods were inserted postovulation in 15 mares during estrus. The mean duration of diestrus was 73.4 ± 36.6 days (mean ± S.D.). Endometrial biopsies showed no significant differences before and after Upod placement. In experiment 2, Upods were inserted regardless of the stage of the estrous cycle in 14 mares. The mean duration of diestrus was 51.3 ± 22.7 days (mean ± S.D). The presence of the Upod was monitored by transrectal ultrasound and an external handheld metal detector. Progesterone was assayed to monitor corpus luteum lifespan, and the mean duration of diestrus was significantly extended in both experiments compared to the control group. Eight mares were randomly selected to be bred the following year, with 100% conception rate post-Upod retrieval.