Death of sperm in the cervix of ewes bearing intrauterine plastic spirals or threads

A plastic spiral intrauterine device (IUD) in the ewe inhibits sperm transport through the cervix. In Exp. 1, plastic spirals were inserted surgically into the lumen of one or both uterine horns. In Exp. 2, Dacron threads were placed in the lumen of each horn. At a subsequent estrus, ewes were mated and necropsied 2 hours later. Sperm were washed from the uterine body and from the anterior, middle and posterior one-third of the cervix and examined. Plastic spirals significantly reduced the percentage of sperm recovered from the uterine body and each segment of the cervix that were motile and live and had normal acrosomes. In the anterior one-third of the cervix, e.g., 49% of the sperm were motile and 66% were live in control ewes but only 17% were motile and 23% were live in IUD ewes. Intrauterine threads also reduced the percentages of sperm that were motile and live in the anterior cervix. Failure of sperm transport in IUD-bearing ewes may be caused by conditions which result in loss of sperm motility in the cervix, thereby inhibiting the establishment of a reservoir of live sperm for transport to the oviducts.