Quercetin Increased Protein Utilization and Decreased Nitrogen Excretion in Broilers by Activating TOR Signaling Pathway

The study was conducted to investigate the effect and mechanism of dietary quercetin supplementation on protein utilization of Arbor Acres （AA） broilers.A total of 240 1-day-old AA broilers were randomly allocated to four treatments with six replicates,comprising 10 broilers each replicate （60 broilers per treatment）.Birds were fed either a corn-soybean meal basal diet without quercetin （control） or a basal diet supplemented with 0.2,0.4 or 0.6 g of quercetin per kg feed,and the trial lasted 42 days.Dietary quercetin supplementation tended to increase the apparent metabolic rate of protein （p=0.076） and the content of serum albumin （p=0.062） in AA broilers.Compared with the control,dietary quercetin supplementation increased the contents of protein in breast muscle （p＜0.05） and in thigh muscle （p=0.053）.In addition,quercetin up-regulated mRNA expression of insulin-like growth factor 1 （IGF-1）,phosphatidylinositol 3-kinase （PI3K）,target of rapamycin （TOR）,ribosomal protein S6 kinase 1 （S6K1）,eukaryotic translation initiation factor 4E （eIF4E）,eukaryotic translation initiation factor 4G （eIF4G）,eukaryotic elongation factor 2 （eEF2） and eukaryotic translation initiation factor 4B （eIF4B） genes and down-regulated mRNA expression of eukaryotic elongation factor 2 kinase （eEF2K） and eukaryotic initiation factor 4E binding protein1 （4E-BP1） genes in breast muscle,thigh muscle and liver of AA broilers （p＜0.05）.The present results suggested that dietary quercetin supplementation enhanced protein utilization in broilers by activating TOR signaling pathway.