Wether bioassay of annual pasture legumes. I. Oestrogenic activity in Medicago tribuloides Desr. var. Cyprus* relative to four strains of Trifolium subterraneum L.

Abstract

The grazing of pasture swards of Cyprus barrel medic and of four strains of subterranean clover resulted in increases of wether teat length similar to those produced by injections of a synthetic oestrogen, diethylstilboestrol. Oestrogenic activity of the medic, as measured by increase in wether teat length, was less than that of the Yarloop and Dwalganup strains of subterranean clover, but similar to that of the Mt. Barker strain. Coumestrol appears to be the principal oestrogenic substance in the medic. The coumestrol contents of Cyprus and commercial barrel medics were similar but varied at different localities. The low coumestrol content of the subterranean clovers suggests that it is not an important oestrogen in this species. ____________________ *Cyprus barrel medic. During the joint FAO–CSIRO collecting expedition in 1950–1951, J. F. Miles collected barrel medic, C.P.J. 13914, in Cyprus, and portion of the seed was passed to D. Symon at the Waite Agricultural Research Institute, Adelaide. A programme, commenced in 1950, to extend the legume belt into the lower rainfall districts of Western Australia, indicated the need for an earlier-flowering medic, and Symon suggested testing the Cyprus introductjon. Encouraging results from sward tnals conducted by the Institute of Agriculture, University of Western Australia, resulted in a programme of seed increase and large-scale commercial production of the Cyprus strain. The Cyprus strain flowers 4 weeks earlier than the commercial and 5 weeks before M. tr ibuloides 173, and is proving a very satisfactory legume on a wide range of soils in Western Australia.