| The objectives of the present study are, 1) to elucidate the effect of daidzein on laying performance and neuroendocinological functions of Shaoxing ducks at the late stage of egg production cycle, 2) to reveal the cellular and molecular mechanisms involved in daidzein action, both in vivo and in vitro.1. Effect of daidzein on laying performance and secretion of related hormones and gene expression in Shaoxing ducksThree hundred and twenty 415-d-old Shaoxing ducks were randomly selected and divided into treatment and control groups, with the basal diet supplemented daidzein at the dosage of 5mg/kg and 0mg/kg, respectively, for the period of nine weeks. The number of eggs, average egg weight and feed intake were recorded daily during the experiment, egg mass was calculated by multiplying average egg weight by egg laying rate, ducks were weighed individually at the start of and the end of the trial. Albumen and yolk of 90 eggs from each group were separated and weighed. At the end of the trial, twenty ducks were sacrificed for blood and tissue sample, the hypothalamus and the pituitary glands were collected. The ovary and oviduct were excised and weighed, meanwhile, the preovulatory follicles in the ovary were counted, the theca and granulosa layers were separated from the largest (F1), the third largest (F3), the fifth largest (F5) and the large white follicle (LWF). The concentrations of some hormones were analyzed by radioimmunoassay (RIA) and the relative abundance of gene expression in tissues was determined by relative quantitative reverse transcription-polymerase chain reaction (RT-PCR).1.1 Effect of daidzein on laying performance of Shaoxing ducksThe egg production of ducks in treatment group increased by 7.70% (P<0.01) compared to the control, there was a trend of increase in average egg weight (P=0.058). The albumen weight improved evidently (P<0.01), while the yolk weight decreased markedly (P<0.05). As a whole, daidzein supplementation significantly increased egg mass by 11.05% (P<0.01) and feed conversion efficiency by 6.44% (P<0.01) . The initial body weight and final body weight were 1839.86± 16.35g and 1798.16±26.73g respectively in treatment group and 1854.65 ± 23.89g and 1698.45±31.45g in control, which suggested that daidzein markedly prevented body weight loss of Shaoxing ducks (P<0.01). There was no significant difference in ovary weight and number of large follicles between two groups, but the oviduct weight significantly elevated by 14.99% (P<0.05) compared to control. These results suggest that daidzein may significantly promote the laying performance of Shaoxing ducks at the late stage of egg production cycle and improve the feed conversionefficiency.1.2 Effect of daidzein on the concentrations of related hormones in Shaoxing ducksNo significant effect of daidzein on serum T3 level was observed, but the concentration of T4 increased markedly (P<0.01). Serum E2 level of ducks in daidzein-treated group was 2.73 times higher (P<0.01) than that in their control counterparts, whereas the leptin concentration did not change. In addition, daidzein significantly increased the plasma cholesterol content by 23.88% (P<0.05) . The significant increase of serum cholesterol, T4 and EI levels may be involved in the mechanisms of daidzein action on improving laying performance of Shaoxing ducks.1.3 Effect of daidzein on the relative abundance of related gene mRNA1.3.1 Distribution of mRNA encoding ER alpha, ER beta , GHR and IGF-1RThe high amount of ERalpha mRNA was detected in the hypothalamus, pituitary and theca and granulosa layers from F1, F3, F5 and LWF follicles of Shaoxing ducks at the late stage of egg production cycle. The ERalpha mRNA level in the theca layer of F1, F3, F5 and LWF did not show a significant difference, but the expression of ER a mRNA was found to decrease evidently in the granulosa layer of LWF. No significant difference was found in ER a mRNA between the theca and granulosa layers of F1, F3 and F5, whereas, in LWF, the granulosa layer expre...
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