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

Abstract

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±0.12g) were randomly allocated to three groups, consisting 8 replicates of 240 eggs each. Three treatments were arranged as non-injected control, 7.5g/L (w/v) NaCl diluent-injected control group, and 10g/L (w/v) Arg solution injected group containing 10g Arg, dissolved in 1L diluent. At 17.5 d of incubation, 0.6mL 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 0.6mL of 10g/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.