Effect of dietary inulin supplements on growth performance and intestinal immunological parameters of broiler chickens

• There was quadratic effect of dietary levels of inulin on feed intake during day 1–21.
• Cecum IgA levels of broilers were increased by inulin supplementation.
• Inulin supplementation improved mucin mRNA expression in jejunum of broilers.
• Inulin supplementation has the potential to enhance intestinal immunity of broilers.

The objective of this study was to assess the effects of dietary inulin supplementation on growth performance and intestinal immune parameters of broilers. A total of 280 one-day-old Cobb 500 male broilers were randomly allocated into four groups of seven replicate pens and given a maize-soybean basal diet supplemented with 0, 5, 10 and 15 g/kg of inulin during the 42 days of the experiment. Feed intake (FI), body weight gain (BWG) and feed conversion ratio (FCR) were determined from d 1 to 21 (starter), and from d 22 to 42 (grower). Intestinal T lymphocyte subpopulations, the production of immunoglobulin A (IgA) and cytokines as well as mucin mRNA expression were measured at 21 d and 42 d. Feed intake was increased quadratically (P=0.001) as the dietary inulin level increasing during starter period only. However BWG and FCR of broilers were not affected by inulin supplementation in either period. At d 21 and as the dietary inulin concentration increasing, proportion of T CD4+ T lymphocyte and CD4+/CD8+ ratio in ileum tissue tended (P=0.05–0.087) to be linearly increased, IgA concentration in cecal content and mucin mRNA expression in jejunum tissue were linearly increased (P=0.006–0.01), whereas concentrations of interleuk-6 and interferon-γ in ileum tissue quadratically (P<0.05) decreased. The effects of dietary inulin on these intestinal immunological parameters were minimal at the 42-d age of broilers. These results indicated that dietary inulin at the levels of 5–10 g/kg may have the beneficial effects on enhancing intestinal immune function of broiler chicken at younger age when the intestinal function is not fully developed.