Assessment of several pasture species, particularly tropical legumes, for oestrogenic activity

Abstract

Several pasture species, mainly legumes of established or potential application to tropical and subtropical pastoral areas, have been assessed for potential oestrogenic activity. The major criterion of potency adopted was the change in the ratio of the concentration of nucleic acids (RNA/DNA) in the uterine tissue of ovariectomized ewes fed exclusively on the test species for 5 days; in one experiment, samples of uterine tissue were obtained by biopsy before and after the experimental treatment. Increases in uterine weight following five daily injections of 10 µg stilboestrol dipropionate or the ad libitum consumption of fresh red clover (Trifolium pratense) appeared to be comparable at c. 50%; both treatments increased the nucleic acid ratio by more than 100%. It was concluded that change in the nucleic acid ratio offered a much more sensitive technique for the detection of small amounts of oestrogen than the traditional uterine weight method; the response obtamed following the ingestion of red clover, a species known to be oestrogenic, demonstrated the applicability of the nucleic acid ratio technique for the detection of phyto-oestrogenicity. No evidence of oestrogenic activity was obtained from the tropical pasture species Desmodium intorturn, Lotononis bainesii, Macroptilium atropurpureum, Lablab puupureus, Trifolium semipilosum or Digitaria decumbens. The results obtained following the feeding of an experimental strain of creeping-rooted lucerne (Medicago sativa) merely suggested a slight potential for oestrogenicity.