Title:

Do insects increase estrogen-like compounds in animal forages?

Perennial forage legumes are important feed components on dairy farms due to their high nutritional quality and positive impacts on milk quality and yield. One potential drawback of forage legumes, however, is their production of phytoestrogens, which can impair animal reproductive performance when consumed in large quantities. Phytoestrogens are naturally synthesized and thought to protect legumes against environmental stressors. Previous research suggests insect pests may influence phytoestrogen concentrations in legumes by triggering their defensive stress response. Despite the fact that a wide range of insects attack legumes, their role in stimulating phytoestrogen accumulation remains unknown. We conducted a greenhouse experiment to quantify the effects of insect herbivory on phytoestrogen accumulation in two perennial forage legume species. Red clover and kura clover were grown in “insect infestation” and “control” treatments in a completely randomized design (CRD) with four replications. Third-instar larvae of Helicoverpa zea were released onto plants in the “infestation” treatment and allowed to feed for seven days. We quantified resulting plant physiological and biochemical variables, including net photosynthesis rate, stomata conductance, transpiration rate, total phenolics, and concentrations of the phytoestrogens formononetin, biochanin A, daidzein, genistein, glycitein, prunetin and coumestrol. Insect herbivory resulted in nearly a doubling of total phytoestrogen concentrations in red clover. Phytoestrogen concentrations were extremely low in kura clover and were unaffected by insect herbivory. Additional research is being conducted to confirm the generality of these results.

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