Phyto-oestrogens in herbage and milk from cows grazing white clover, red clover, lucerne or chicory-rich pastures

A grazing experiment was carried out to study the concentration of phyto-oestrogens in herbage for cattle and in milk during two periods (May and June). Forty-eight Danish Holstein cows were divided into four groups with four treatment diets; white clover, red clover, lucerne and chicory-rich pastures. Each experimental period lasted 15 days. Herbage samples from the first day and individual milk samples from the last day of the experimental period were analysed for phyto-oestrogens using LC-MS technique. The total concentration of phyto-oestrogens was 21 399 mg/kg dry matter (DM) for red clover and 238 to 466 mg/kg DM for the other three herbages mainly due to a much higher concentration of biochanin A, formononetin and glycitein in red clover. In the milk, the total concentration of phyto-oestrogens was 253 to 397 μg/l for red clover milk and 56 to 91 μg/l in the milk from the other three treatments. This was especially due to a higher concentration of equol, daidzein and formononetin in the red clover milk. The concentration of biochanin A was significantly higher in milk from the red clover treatment in May while no differences were observed in June. Enterodiol was similar across treatments while the concentration of enterolactone was significantly lower for red clover milk compared with the other treatments. Of the tested pastures, red clover appears to have the highest concentration and to be the best source of phyto-oestrogens, especially equol, in bovine milk.