Safety evaluation of daidzein in laying hens: Part I. Effects on laying performance, clinical blood parameters, and organs development

Daidzein, an estrogen-like product, becomes 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 hen safety study was conducted to examine if the high-dose daidzein could affect the safety of hens selves, including laying performance, clinical blood parameters and organs development. Seven hundred and sixty-eight 56-week-old Hyline Brown were randomly assigned to 4 groups with 8 replicates of 24 birds each and 3 weeks later fed diets supplemented with 0, 10, 50 and 100 mg of daidzein/kg for 12 weeks. The mortality was significantly decreased (P < 0.05). No treatment related adverse clinical signs were observed. Mean egg production, egg mass and feed conversion of whole experiment period was significantly influenced by dietary daidzein supplement (P < 0.05), showing significant quadratic response to increasing dietary daidzein supplement (P = 0.029, P = 0.003 and P = 0.019, respectively). There was no statistically significant changes in haematology (P > 0.05). In clinical chemistry parameters, total protein, total cholesterol, calcium and phosphorus were significantly affected by dietary daidzein supplement (P < 0.05). The no observed adverse effect level (NOAEL) is considered to be 50 mg/kg.