| Abstract
| - Our previous studies demonstrated that dietary daidzein improves egg production in ducks duringthe late period of the laying cycle. The present study was aimed to investigate the effect of daidzeinin laying hens, with more focus on eggshell quality. The expression of ER-α, GH-R, and IGF-IRmRNA in shell glands was determined to identify the target genes of daidzein action and to revealthe relationship between shell quality and profiles of gene expression in shell glands of laying hens.1000 ISA hens, at 445 days of age, were allotted at random to two groups and given the basal dietwith or without 10 mg of daidzein per kg diet for 9 weeks. Daidzein supplement significantly increasedthe egg laying rate and the feed conversion ratio. The eggshell thickness increased, while thepercentage of cracked eggs decreased in daidzein-treated hens. Serum E2 and phosphateconcentrations were not altered, but the level of serum Ca2+ and the tibia bone mineral density weresignificantly increased in the daidzein-treated group compared with their control counterparts. In parallelwith the significant increase of oviduct weight, significant down-regulation of GH-R and IGF-IR mRNAand a trend of decrease in ERα mRNA expression in shell glands were observed in daidzein-treatedhens. The results indicate that dietary daidzein improves egg laying performance and eggshell qualityduring the late (postpeak) laying stage of hens, which is associated with modulations in geneexpression in the shell gland. Keywords: Daidzein; egg laying performance; shell gland; gene expression; ISA hens
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