Soy Phytoestrogens

Genistein, a soy phytoestrogen, is a powerful antioxidant found in soybean. A study was conducted to determine the effects of dietary genistein supplementation on Japanese quail (Coturnix coturnix japonica) laying performance and egg yolk contents of malondialdehyde (MDA), vitamin A, and vitamin E. Malondialdehyde is an indicator of lipid peroxidation, whereas vitamins A and E have antioxidant properties. One hundred and fifty birds, five weeks of age, were randomly assigned to one of three treatments consisting of 50 birds (five replicates of ten) and were fed a basal diet or the basal diet supplemented with either 400 or 800 mg of genistein/kg of diet. The experimental period lasted 90 days with a 17 hour light and 7 hour dark photoperiod schedule. Dietary genistein supplementation (800 mg/kg) increased feed intake, egg production, egg weight, Haugh unit, shell thickness, and shell weight and improved feed efficiency at a greater extent than the other levels (0 and 400 mg/kg). Egg yolk genistein concentration was increased (P < 0.0001), whereas egg yolk MDA concentration was decreased (P < 0.0001) at the highest level of genistein supplementation. However, genistein supplementation did not affect egg yolk daidzein, vitamin A, and vitamin E levels. There was an inverse relationship between egg yolk genistein and MDA concentration (R2 = 0.74, P < 0.0001). Results of the present study indicate that supplementing with dietary genistein (800 mg/kg) improved performance, egg quality, and egg yolk genistein content and decreased egg yolk MDA concentration in quail. (Note-the real significance of this study was that feeding ultra-high levels of a soy phytoestrogen did not cause production problems in this model system and the results should apply to other poultry species).

Akdemir, K. and K. Sahin. 2009. Genistein supplementation to the quail: Effects on egg production and egg yolk genistein, daidzein, and lipid peroxidation levels. Poultry Sci. 88:2125-2131.