Increased sperm death in the cervix and uterus of estrous ewes after regulation of estrus with prostaglandin or progestogen.

One-hundred and twenty-three ewes were used in three experiments designed to determine whether the regulation of estrus, by administration of either prostaglandin F2 a (PG) to regress corpora lutea or medroxyprogesterone acetate (MAP) to control the length of the estrous cycle, would increase sperm death in the reproductive tract at the ensuing estrus. Ewes were treated either with PG injected IM on day 10 of an estrous cycle or with a MAPimpregnated intravaginal sponge from day 6 to 14 or from day 10 to 23. Ewes were in estrus and were mated 2 days after PG treatment and 2 or 3 days after withdrawal of MAP sponges. Control ewes were mated at a natural unregulated estrus. Ewes were neeropsied at 2 or 4 hr after mating. Sperm were washed from the uterine body; from the anterior, middle and posterior thirds of the cervix, and from the anterior vagina (Exp. 1 and 2), or from only the three segments of the cervix (Exp. 3). Viability of sperm was assessed from motility estimates, by live-dead staining and by acrosomal morphology. In the first two experiments, PG or MAP treatment significandy reduced the percentages of sperm that were motile and unstained and had normal acrosomes. Reductions were greater in the uterine body and anterior third of the