Abstract: 【Objective】 This study was aimed to investigate the effect of 1,8-cineole on antioxidant indexes and alterations in metabolic components of eggs,and antioxidant signaling pathways in laying hens,thereby offering a scientific foundation for the judicious incorporation of 1,8-cineole into the dietary of laying hens. 【Method】 320 Hy-Line Brown laying hens,all 46 weeks old with similar egg production and body weights,were randomly divided into 2 groups,with 10 replicates in each group and 16 chickens in each replicate.Laying hens in control group were fed with basic feed,while hens in experimental group were given the same diet with an addition of 40 mg/kg 1,8-cineole.After a 7-day pre-trial,a 56-day trial followed,during which daily measurements of production performance and egg quality were taken.Blood,liver tissues,and eggs were collected on the 7th,28th,and 56th days of the trial.Eggs were divided into two groups and stored at 4 ℃ for 30 and 40 days,respectively.Albumen,yolk,and serum were analyzed for total antioxidant capacity (T-AOC),total superoxide dismutase (T-SOD),glutathione (GSH) activity,and malondialdehyde (MDA) content.High-resolution non-targeted metabolomics analysis was employed to identify the types and relative contents of metabolic products present in egg yolks.Concurrently,Real-time quantitative PCR was utilized to assess the expression of nuclear factor erythroid 2-related factor 2 (Nrf2),NADPH quinone oxidoreductase 1 (NQO1),small Maf proteins (sMaf),and heme oxygenase-1 (HO-1) genes in liver of laying hens. 【Result】 Compared with control group,①During the experimental period of 29-56 days,the egg laying rate of hens in experimental group was significantly increased (P＜0.05),while the soft broken egg rate was significantly decreased (P＜0.05).There were no significant changes in average egg weight,average daily feed intake,and mortality rate (P＞0.05).Laying hens in experimental group exhibited a statistically significant increase in Haugh unit of eggs on the 28th and 56th days (P＜0.05).No significant differences were observed in yolk ratio,egg shape index,and eggshell thickness (P＞0.05).②On the 7th,28th,and 56th days,the activities of T-AOC and SOD in both albumen and yolk,as well as GSH activity in yolk,were significantly increased (P＜0.05),while MDA content in albumen was significantly decreased (P＜0.05).③The metabolite profiles in yolk showed significant alterations,with 365 up-regulated and 218 down-regulated metabolites under positive ion mode,and 105 up-regulated and 89 down-regulated metabolites under negative ion mode.Notably,such as choline and taurine expression were significantly increased (P＜0.05).④The T-AOC,and the activities of GSH and SOD in serum of laying eggs were significantly increased (P＜0.05).⑤The expression of Nrf2,ssMaf,and NQO1 genes in liver of laying hens were significantly increased (P＜0.05). 【Conclusion】 Under the conditions of this experiment,dietary supplementation with 1,8-cineole could enhance the antioxidant capacity of both eggs and laying hens,potentially contributing to an extended shelf life of eggs.

Key words: 1,8-cineole; laying hens; eggs; metabolites; antioxidant capacity