Influence of cutting frequency and height on phytoestrogen levels in red clover and white clover

Abstract Phytoestrogens are a class of secondary compounds naturally produced by some forage legumes, including red clover ( Trifolium pratense L.) and white clover ( Trifolium repens L.). Previous research showed that phytoestrogens can have beneficial and negative effects on animal health and reproductive function. Determining whether and how common agronomic practices influence the phytoestrogen profiles of legume forages would inform strategies for better managing ruminant exposure to phytoestrogens. A field experiment was conducted to evaluate how cutting frequency (cutting 3 vs. 5 times per growing season, hereafter 3x vs. 5x) and height (cutting to 5 cm vs. 10 cm residual height) influence phytoestrogen accumulation in red and white clover. The results revealed that total phytoestrogen concentrations were on average 5.01 mg g −1 dry matter in red clover and 0.07 mg g −1 dry matter in white clover. Formononetin and biochanin A were the major phytoestrogen compounds in both species, together accounting for 85% (red clover) and 65% (white clover) of the total measured phytoestrogens. Cutting frequency strongly influenced phytoestrogen concentrations in both species. In red clover, differences in total phytoestrogen concentration in the 5x relative to the 3x ranged from 33.6% to 83.5%, depending on the specific cutting event. In contrast to frequency, cutting height influenced phytoestrogen concentrations in white clover only. These findings indicate that harvest schedule may be an important management lever for moderating phytoestrogen concentrations in these common and important forage species.