摘要This study was aimed to investigate the effects of dietary calcitriol or quercetin supplementation on eggshell and bone quality of laying hens.In trial 1,72 Hy-Line Brown layers(80-week-old)with weak-shelled strength(25 to 30 N)were assigned into 4 dietary treatments with 6 replicates of 3 birds and fed a basal diet(4％calcium level)or basal diets supplemented with 0.5％calcium,5 μg/kg calcitriol or 500 mg/kg quercetin for 4 weeks.In trial 2,360 Hy-Line Brown layers(60-week-old)were divided into 3 groups with 8 replicates of 15 birds:control group(basal diet),calcitriol group(basal diet+5 μg/kg calcitriol),and quercetin group(basal diet+500 mg/kg quercetin).This trial lasted for 12 weeks.The results showed that dietary calcitriol or quercetin improved eggshell quality in both trials(P＜0.05).In trial 2,compared with the control group,both calcitriol and quercetin supplementations improved femoral bone quality,calcium retention of hens and calcium content in uterine fluid at 18.5 h post-oviposition(PO)(P＜0.05),along with enhancing uterine morphology.Compared to the control group,supplemental calcitriol or quercetin up-regulated the relative mRNA expression levels of uterine transient receptor potential cation channel,subfamily V,member 6(TRPV6)at 8.5 h PO and plasma membrane calcium-ATPase(PMCA),vitamin D receptor(VDR),estrogen receptor alpha(ERα)at 18.5 h PO(P＜0.05),but down-regulated the uterine caspase 3(CASP3)relative mRNA expression level at 8.5 h PO(P＜0.05).Meanwhile,the femoral relative mRNA expression levels of tartrate-resistant acid phosphatase(TRAP)(up-regulated at 8.5 and 18.5 h PO)and alkaline phosphatase(ALP)(up-regulated at 8.5 h PO but down-regulated at 18.5 h PO)were also affected by calcitriol or quercetin supplementation(P＜0.05).Compared to the calcitriol,quercetin increased hen-day egg production and femoral medullary bone volume/bone tissue volume but reduced femoral stiffness(P＜0.05),which were accompanied by increased relative mRNA expression levels of uterine TRPV6,estrogen receptor beta(ERβ)at 18.5 h PO(P＜0.05).Overall,both dietary calcitriol and quercetin could improve eggshell and bone quality by modulating calcium metabolism of aged layers.Compared to calcitriol,dietary quercetin up-regulated the expression of uterine calcium transporters,without affecting eggshell quality.