Route of progestagen administration to the ewe and spermicidal action in the vagina at the ensuing estrus.

Parous ewes were treated orally with medroxyprogesterone acetate (MAP) or melengestrol acetate (MGA), subcutaneously with progesterone, or intra-vaginally with MAP, MGA or progesterone. Treatment was begun on day 8 of an estrous cycle and continued for 17 days. When the ewes were in estrus after progestagen withdrawal, they were inseminated artitlcally and their vulvo-vaginal junctions were ligated to prevent sperm cell drainage to the exterior. The ewes were killed 22 hrs later, their vaginas flushed, and intact sperm cells and tailless sperm heads counted. The oral, subcutaneous or intravaginal administration of progestagen increased the numbers of sperm cells recovered as tailless heads, indicating stimulation of sperm-breaking mechanisms in the vagina at the ensuing estrus. Progestagen given intravaginally decreased the total number of sperm cells recovered, indicating increased sperm cell disappearance within the vagina.