Dr Kevin Foster1, Dr Daniel Kidd2, Dr Joanne Wisdom3, Ms Evonne Walker3, Prof. Megan Ryan3
1Department of Primary Industries and Regional Development, Perth, Australia, 2Grower Group Alliance, Perth, Australia, 3The University of Western Australia, Perth, Australia
Biography:
Dr Kevin Foster has worked with pastures for his entire career. Kevin's research has encompassed perennial and annual pasture legumes, particularly tedera and subterranean clover. Recently, whilst at UWA, Kevin focussed his research on oestrogenic pastures. Kevin now works at DPIRD where he works across a broad range of projects.
Abstract:
High levels of the phytoestrogen formononetin (F) in green leaves of older cultivars (cvs) of subterranean clover (Trifolium subterraneum)—notably Dinninup, Dwalganup, Geraldton and Yarloop—can cause both transient and permanent fertility issues in ewes, as well as increased lamb and ewe mortality (clover disease). Cultivars bred for low F were released to solve this problem. To investigate if old high-F cvs have persisted in pastures, we examined clover leaf samples submitted by producers from across southern Australia. Cultivars were identified by morphological characters and F concentration. Isoflavones (F, genistein, biochanin A) were measured with thin-layer chromatography and leaf K, P and S concentrations were measured by inductively coupled plasma-optical emission spectrometry. Of 577 samples analysed, 60% contained F above the current ‘safe’ level of 0.20% of leaf dry weight, with the highest average F (0.90%) measured in samples from South Australia. Concentrations of F varied greatly among samples of individual cvs suggesting impacts of management or environment but were not related to leaf nutrient concentrations. The most common cvs submitted was Dinninup, particularly for South Australia and Western Australia. The paucity of relatively modern low-F cultivars suggests that producers submitted samples they suspected to be high-F cvs, possibly due to evidence of ewe reproductive or animal health issues. Due to this bias, these results do not provide a quantitative assessment of the occurrence of old high-F cvs, but they do suggest a much greater prevalence than desirable and a need for pasture renovation with new low-F cultivars.