Safety evaluation of daidzein in laying hens: Part II. Effects on calcium-related metabolism

Daidzein, an estrogen-like product, has become increasingly popular as a dietary supplement, particularly for postpeak-estrus animals seeking a safe natural alternative to play a role of estrogen. However, there is little available safety data of it for raisers and consumers. A subchronic laying hensafety study has been conducted to examine if the high-dose daidzein could affect calcium-related metabolism (eggshell quality and bone mineralization). Seven hundred and sixty-eight 56-week-old Hyline Brown were randomly assigned to 4 groups with 8 replicates of 24 birds each (192 laying hensper group) and 3 weeks later fed diets supplemented with 0(control), 10, 50 and 100 mg of daidzein/kg for 12 week. Eggshell thickness, eggshell percentage, eggshell strength, eggshell Ca concentration was increased linearly with increasing dietary daidzein supplementation (P = 0.001, P = 0.007, P = 0.002 and P = 0.000, respectively). Serum Ca increased linearly with increasing dietarydaidzein supplementation (P = 0.042), and serum P showed a significant quadratic response to dietarydaidzein supplementation (P = 0.036). Bone ash and bone Ca were significantly influenced by dietarydaidzein supplementation (P < 0.05). These findings indicate that daidzein hold no observed adverse effect on calcium metabolism, but also a safe and effective food additive for calcium metabolism in animals and humans.