Change with length of feeding period in the oestrogenic response to ovariectomized ewes to ingested coumestans

Abstract

Three experiments were conducted to test the effect of the period of intake of feed containing coumestans, and the amount of coumestans in the feed, on the production of cervical mucus in ovariectomized ewes.

After long periods of feeding of medic cubes, ewes produced much less mucus than after shorter periods of feeding when feed containing 525 ppm coumestrol and 935 ppm 4'-methoxycoumestrol was ingested. When feed containing approximately one-third of these amounts of coumestans was ingested, the production of cervical mucus initially increased, being greater after 4 than 1 day's exposure to the feed. After 8–16 days of feeding on these diets, ewes produced the same amount of mucus as those fed on a non-oestrogenic diet.

The decline in the cervical mucus response suggested either that a deactivation mechanism for coumestans develops in the ewe, or that the ewe becomes refractory to coumestans.