Sperm transport into the cervix of the ewe after regulation of estrus with prostaglandin or progestogen.

Mature ewes (12 per group) were given prostaglandin F20t (PG; 10 mg intramuscularly) on day 10 of an estrous cycle, to regress corpora lutea, or on day 16, after natural corpus luteum regression. Ewes treated on day 10 or 16 were in estrus on day 12 or 17, respectively. The PG-treated and untreated ewes were mated at estrus and necropsied 2 hr later. Sperm were counted in the oviducts, the uterus and the anterior, middle and posterior segments of the cervix. Sperm numbers were reduced in all three segments of the cervices of ewes treated with PG on day 10 but not in ewes treated on day 16. The results suggest that some factor associated with shortening of the estrous cycle inhibited sperm transport. Other ewes were treated with 60 mg of medroxyprogesterone acetate (MAP) by intravaginal sponge from day 6 to 14, 6 to 22 or 14 to 22 of an estrous cycle and mated at the ensuing estrus, 2 or 3 days after MAP withdrawal. Sperm numbers in the anterior cervix 2 hr after mating were reduced in all MAP-treated ewes, and sperm numbers in the entire cervix were significantly lower in the 6 to 14 day group than in the other MAP-treated ewes. In the ewes treated from day 6 to 14, endogenous progesterone secretion was similar to that of untreated ewes through day 14, and estrous cycles averaged 16.8 days in length. Thus, MAP treatment reduced sperm numbers in the cervix