Cervical mucus measurement in ovariectomized ewes as a bioassay of synthetic and phyto-oestrogens

Abstract

Increases in weight of cotton swabs placed into the anterior vagina were used as a measure of cervical mucus production in ovariectomized ewes. Dose response lines were obtained from graded doses of stilboestrol.

Pretreatment with a series of progesterone injections was necessary for significant responses. Daily doses of 5 mg of progesterone prior to feeding resulted in a shorter period of response than doses of 10 and 20 mg.

A bioassay of three strains of Trifolium subterraneum L. (cv. Dinninup, Dwalganup, and Woogenellup) and Lolium rigidum Gaud. with cervical mucus measurement showed significant differences in oestrogenic activity. Such differences appeared to be related to the formononetin content of the pastures. Responses were evident 1 day after the commencement of feeding and did not change on the second day.

Highest precision in the calibration of stilboestrol responses was obtained when log mucus weight was regressed on log (dose (µg) + l). Indices of precision were comparable with the best published for other forms of sheep bioassay.