a1 State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, People's Republic of China
a2 Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
a3 Livestock Behavioral Research Unit, United State Department of Agriculture, Agricultural Research Service, West Lafayette, IN, USA
In the present study, two experiments were conducted to investigate the effect of dietary l-arginine (Arg) supplementation on the inflammatory response and innate immunity of broiler chickens. Expt 1 was designed as a 2 × 3 factorial arrangement (n 8 cages/treatment; n 6 birds/cage) with three dietary Arg concentrations (1·05, 1·42 and 1·90 %) and two immune treatments (injection of lipopolysaccharide (LPS) or saline) given at an interval of 48 h between 14 and 21 d of age. In Expt 2, correlation between dietary Arg concentration (0·99, 1·39, 1·76, 2·13 or 2·53 %) and percentage of circulating B cells (percentage of circulating lymphocytes) was determined. In Expt 1, LPS injection decreased body-weight gain and feed intake and increased feed conversion ratio of the challenged broilers (14–21 d; P< 0·05). LPS injection suppressed (P< 0·05) the percentages of splenic CD11+ and B cells (percentages of splenic lymphocytes) and phagocytic activity of splenic heterophils and macrophages; Arg supplementation linearly decreased the percentages of CD11+, CD14+ and B cells in the spleen (P< 0·10). LPS injection increased (P< 0·05) the expression of IL-1β and IL-6 mRNA in the spleen and caecal tonsils. Arginine supplementation decreased (P< 0·05) the expression of IL-1β, Toll-like receptor 4 (TLR4) and PPAR-γ mRNA in the spleen and IL-1β, IL-10, TLR4 and NF-κB mRNA in the caecal tonsils. In Expt 2, increasing dietary Arg concentrations linearly and quadratically reduced the percentage of circulating B cells (P< 0·01). Collectively, Arg supplementation attenuated the overexpression of pro-inflammatory cytokines probably through the suppression of the TLR4 pathway and CD14+ cell percentage. Furthermore, excessive Arg supplementation (1·76 %) suppressed the percentages of circulating and splenic B cells.
(Received June 06 2013)
(Revised October 08 2013)
(Accepted October 13 2013)
Abbreviations: Arg, l-arginine; BW, body weight; FCR, feed conversion ratio; FI, feed intake; FSC, forward-scatter characteristics; iNOS, inducible NO synthase; LBP, LPS-binding protein; LPS, lipopolysaccharide; MyD88, myeloid differentiation factor 88; PBMC, peripheral blood mononuclear cells; RPMI, Roswell Park Memorial Institute; SSC, side-scatter characteristics; Th, T helper; TIRAP, Toll-IL 1 receptor domain-containing adaptor protein; TLR4, Toll-like receptor 4; TRAM, Toll-IL 1 receptor domain-containing adaptor inducing interferon-related adaptor molecule; TRIF, Toll-IL 1 receptor domain-containing adaptor inducing interferon