The sheep study was performed according to NIH guidelines at Colorado State University, a facility accredited by the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC). Protocols were approved by Institutional Animal Care and Use Committees at Colorado State University (Fort Collins, CO, USA; Animal Welfare Assurance Number: A3572-01) under approval #12-3704A. Implantation of IVRs was performed under minimal physical restraint without causing undue stress or pain to the sheep. Sheep were flipped, hooded and hobbled, and placed in lateral recumbency. The perineal region was prepped with multiple scrubs of povidine iodine alternated with isopropyl alcohol. The device was inserted into the cranial vagina using a sterile gloved finger lubricated with medical-grade lubricant gel. A non-absorbable nylon suture tied to the IVR was allowed to extend outside of the vulva to indicate that the ring had not been expelled, and to aid in removal of the ring during removal/reinsertion procedures. Sheep were minimally restrained while the IVR was removed from the vagina using a suture traction. Devices were re-inserted using similar methods. The study was non-terminal.