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In ovo feeding of vitamin C (VC) has positive effects on the growth performance, immune and antioxidant function in poultry, which indicates that increasing VC content in eggs may be of benefit. This study was to investigate the effects of dietary VC supplementation on VC synthesis and transportation and egg deposition. In Exp. 1, in order to select a suitable animal model, VC content was detected in different eggs from different layer species. Vitamin C content was lower in ISA Brown breeder eggs and Hy-Line Brown layer eggs ( P < 0.05) then in Arbor Acres breeder eggs. In Exp. 2, a total of 24 Hy-Line Brown layers (42-week-old) were randomly divided into 3 treatments with 8 replicates and fed a basal diet with VC at 0, 200 and 400 mg/kg. Sodium-dependent VC transporter 1 and 2 ( SVCT1 and SVCT2 ) expressions were higher in ileum than in duodenum and jejunum ( P < 0.05). SVCT1 expression was higher but SVCT2 expression was lower in the magnum than in the ovary ( P < 0.05). L-Gulonolactone oxidase ( GLO ) and SVCT1 expressions were higher but SVCT2 was lower in the kidney than in the liver ( P < 0.05). Dietary VC supplementation at 400 mg/kg increased SVCT1 expression in duodenum, ovary and magnum, but decreased GLO and SVCT1 expression in liver ( P < 0.05). Dietary VC supplementation at 200 and 400 mg/kg increased SVCT2 expression in duodenum, but decreased GLO and SVCT1 expression in kidney and SVCT2 expression in liver ( P < 0.05). Dietary VC supplementation promoted VC absorption in duodenum and jejunum, but reduced endogenous VC synthesis in liver and kidney. Although dietary VC supplementation enhanced VC transportation in ovary and magnum, it did not increase VC deposition in produced eggs.

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Abstract Background: Some previous studies have indicated that in ovo feeding (IOF) of vitamin C (VC) had positive effects on the performance in poultry. In order to realize embryonic VC supplementation, an idea about hen’s dietary VC supplementation to achieve VC enrichment in produced eggs was proposed. And this study was executed to investigate the effects of dietary VC supplementation on synthesis and transportation of VC in layers and VC deposition status in produced eggs.Results: Compared with Arbor Acres breeder eggs, egg VC content was lower in Isa Brown breeder eggs and Hy-Line Brown layer eggs (P < 0.05). Sodium-dependent vitamin C transporter 1 (SVCT1) and SVCT2 expression was higher in ileum than in duodenum and jejunum (P < 0.05). SVCT1 expression was extremely higher in magnum than in ovary, while SVCT2 expression was lower (P < 0.05). L-gulonolactone oxidase (GLO) expression was extremely higher and SVCT1 expression was higher in kidney than in liver, while SVCT2 was lower (P < 0.05). 400 mg/kg VC supplementation increased SVCT1 expression in duodenum, ovary and magnum, while decreased GLO and SVCT1 expression in liver (P < 0.05). 200 and 400 mg/kg VC supplementation increased SVCT2 expression in duodenum, while decreased GLO and SVCT1 expression in kidney and SVCT2 expression in liver (P < 0.05).Conclusions: Hy-Line Brown layer was a useful model for investigating effects of dietary VC supplementation on VC deposition in produced eggs. Dietary VC supplementation promoted VC absorption in duodenum and jejunum, but reduced endogenous VC synthesis in liver and kidney. Although dietary VC supplementation enhanced VC transportation in ovary and magnum, it finally failed to increase VC deposition in produced eggs.