Sponges impregnated with medroxyprogesterone acetate (MAP) were left in the vaginae of parous ewes from 8 to 25 days after oestrus. The ewes were inseminated with 0·25 ml of fresh ram semen 45 hr after removal of the sponges. Ewes in natural oestrus were inseminated as controls. In half of the ewes of each group, the reproductive tract was ligated at the vulvovaginal junction at the time of insemination to prevent the loss of sperm cells by drainage. Ewes were killed 24 hr after insemination and the number of spermatozoa in each segment of the reproductive tract was estimated.
While 62% of the spermatozoa were recovered from ewes in which the vulvovaginal junction was ligated, less than 1% were recovered from the ewes with unligated tracts, indicating the loss of large numbers of sperm cells by drainage. Fewer spermatozoa and a higher proportion of tailless sperm heads were recovered from ewes treated with MAP than from control ewes.