Effects of in ovo feeding of l-arginine on the development of lymphoid organs and small intestinal immune barrier function in posthatch broilers

The present study was conducted to investigate the effects of in ovo feeding of l-arginine (Arg) solution on the nitric oxide synthase (NOS) activity and nitric oxide (NO) production, jejunal inducible NOS (iNOS) gene promoter methylation status and expression level, immunological cytokines and toll-like receptors mRNA expression in small intestine of broiler chickens. After candled on 16 d of incubation, a total of 720 embryonated eggs with similar weight (65.08 ± 0.12 g) were randomly allocated to three groups, consisting 8 replicates of 240 eggs each. Three treatments were arranged as non-injected control, 7.5 g/L (w/v) NaCl diluent-injected control group, and 10 g/L (w/v) Arg solution injected group containing 10 g Arg, dissolved in 1 L diluent. At 17.5 d of incubation, 0.6 mL of each solution was injected into the amniotic fluid of each egg of injected groups. Results showed that in ovo feeding of Arg solution increased (P < 0.05) the activity of iNOS, the contents of interleukin-2 (IL-2), interleukin-4 (IL-4) and secretory immunoglobulin A (sIgA), the mRNA expressions of toll-like receptor-2 and toll-like receptor-4 in intestinal mucosa, and the mRNA expression and protein abundance of iNOS. In addition, in ovo feeding of Arg solution decreased (P < 0.05) the iNOS promoter methylation percentage in jejunal mucosa compared with non-injected control and diluent-injected group. Meanwhile, the iNOS activity, the contents of NO, IgA, IL-2 and IL-4 in serum as well as the absolute weights of lymphoid organs in Arg group were higher (P < 0.05) than other groups. Collectively, our data indicated that in ovo feeding of 0.6 mL of 10 g/L (w/v) Arg solution facilitated improving the immunological barrier functions in intestinal mucosa and the overall immunity of 21-d-old broilers by suppressing the iNOS methylation and activating the Arg-NO signaling pathway. Therefore, in ovo feeding of appropriate Arg solution could be as an effective technology for regulating early nutrition supply and subsequent the immune function in poultry industry.