Impact of phyto-oestrogens on reproductive health of sheep

Phyto-oestrogens are plant compounds that mimic the effects of oestrogen. They are mainly found in legumes, especially red and subterranean clover and lucerne. Levels vary with cultivar, season, growing stage and stress to the plant. Consumption of oestrogenic pasture or conserved forage has been shown to have negative effects on reproductive performance of sheep — in particular, a decrease in fecundity and an increase in barren rate. Prolonged exposure may lead to irreversible changes to cervical structure and reproductive performance. Evidence for the impact of phyto-oestrogens on cattle is much weaker than for sheep. The many advantages of clover and lucerne should be exploited, but an understanding of phyto-oestrogenism is needed to avoid unwanted negative impacts on livestock reproductive performance.