Dose-dependent effects of dietary quercetin on performance, egg quality, metabolic health, and antioxidant defense in laying hens: A systematic review and meta-analysis

초록

Background and Aim: Quercetin is a plant-derived flavonoid known for its antioxidant and metabolic regulatory properties. Many studies have assessed its effects on laying hen performance, egg quality, blood metabolites, and oxidative status; however, the results have been inconsistent, mainly due to differences in dosage, duration, hen age, and quercetin form. This meta-analysis aims to quantitatively synthesize the available evidence and examine the dose-response relationships of dietary quercetin supplementation on productive performance, egg quality traits, blood metabolites, and antioxidant defenses in laying hens. Materials and Methods: A systematic literature search of Scopus and Web of Science identified 27 eligible studies published in English. Effect sizes were calculated as mean differences (MDs) using a restricted maximum likelihood random-effects model. Subgroup and meta-regression analyses were conducted to evaluate how quercetin dose, treatment duration, initial hen age, and quercetin form (extract vs. plant powder) influenced the outcomes. Heterogeneity was assessed with the I & sup2; statistic, and publication bias was examined using funnel plots and Egger's regression test. Results: Dietary quercetin significantly improved laying rate (LR) (MD = 2.82%), egg weight (MD = 1.21 g), Haugh unit (MD = 1.84%), shell thickness (MD = 0.014 mm), and yolk color (MD = 0.53), while reducing the feed-to-egg ratio (FER) (MD = -0.15) (p < 0.05). Quercetin supplementation also decreased serum glutamate pyruvate transaminase (SGPT), glucose, total cholesterol, and malondialdehyde levels, while increasing high-density lipoprotein and superoxide dismutase (SOD) concentrations (p < 0.05). Meta-regression revealed linear dose-dependent reductions in SGPT, glucose, and total cholesterol, whereas LR, FER, and SOD activity showed quadratic responses. Optimal responses occurred at quercetin doses of approximately 400-600 mg/kg. Treatment duration, hen age, and quercetin form further influenced several outcomes. Conclusion: Dietary quercetin effectively boosts productivity, egg quality, metabolic health, and antioxidant defense in laying hens in a dose-dependent way. Supplementing at 400-600 mg/kg seems optimal for maximizing laying performance and antioxidant levels, supporting quercetin as a promising phytogenic feed additive for sustainable poultry farming.

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