Effects Of In Ovo Daidzein Injection On Early Posthatch Growth And Expression Of Growth-Related Genes In The Chicken

In this study,in ovo injection of daidzein was used to investigate the effect of early embryonic daidzain exposure on posthatch growth of broiler chickens.Serum levels of thyroid hormones and growth-related genes in hypothalamus and liver were analyzed to reveal the underlying mechanism.1 Effect of daidzein administration in ovo on early posthatch growthOn day 7 of embryonic age,fertile eggs of Sanhuang small D were randomly allocated to Control and Daidzein groups,which were injected with 100μL of white mineral oil or 1 mg/ml daidzein-oil solution.Body weight was recorded weekly.At day 1 and 21 posthatch (D1 and D21),blood and tissue samples were collected for further analysis.No significant difference was observed on hatch weight between these two groups,but the Daidzein group exhibited faster growth rate after hatching,which resulted in significantly greater body weight than that of control at D21(P＜0.05).On D1,gastrocnemius weight and gastrocnemius ratio were all reduced in males,yet daidzein significantly increased liver index and reduced pectoralis major weight in females.On D21,however,daidzain administration in ovo significantly reduced liver index but increased gastrocnemius weight, gastrocnemius ratio,pectoralis major weight and pectoralis major ratio in males,and reduced liver index but increased gastrocnemius weight in females.The serum T₄,T₃,fT₃ and Estradiol were tested with RIA.Results indicated that there was no significant changes on serum hormone levels at 1D.On D21,there is no differernce were detected on T₄,and daidzein administration significantly reduced T3 level in males and fT3 in females.Daidzein group had significantly higher E level in females.2 Effect of daidzein administration in ovo on expression of growth related genes in hypothalamus and liverHepatic GHR,IGF-I and IGF-IR and hapathalamic SS,TRH and FTO mRNA expression were determined with relative quantitative real-time PCR on D21.Daidzein group had significantly higher hepatic expression of GHR and IGF-I but similar IGF-IR mRNA compared with Control group.In hypothalamus,daidzain administration in ovo significantly reduced SS mRNA expression in male chickens,but not in females.Besides, daidzain in ovo tended to enhance TRH transcripts in males(P=0.07) and significantly increased its expression in females.No difference was found between the two groups on CRH mRNA expression.Interestingly,FTO mRNA in hypothalamus was significantly enhanced by daidzain treatment.These results indicate that embryonic exposure to daidzein exerts a long-term effect on posthatch growth by modification of growth-related gene expression in liver and hypothalamus of chickens.