Formononetin content of ‘Grasslands Pawera’ red clover and its oestrogenic activity to sheep

Abstract

The formononetin content of the leaf material of Pawera red clover was measured on four occasions during the year, and concomitantly the oestrogenic activity of Pawera red clover pasture to ewes was estimated using the bioassay production of cervical mucus. Both formononetin concentration (% dry matter basis) and oestrogenic activity (μ g equivalents of oestradiol‐17β) varied significantly between assays, the respective values being January — 0.64%, 15.5 μg; March — 1.38%, 32.5 μg May — 0.84%, 9.2 μ g; November — 0.80%, 35.2 μ g. When hay was made from Pawera the concentration of formononetin in the leaf material fell from 0.95% in the green pasture to 0.43% in the hay. Ewes fed this hay produced responses equivalent to 1.9 μg of oestradiol‐17β. The relevance of these findings to sheep management and fertility is discussed.