Effects of dietary glycine supplementation and fish meal on inflammatory responses in broiler chicks

1. The effect of dietary protein source and glycine (Gly) supplementation on inflammatory responses was investigated using broiler chicks. Birds (7 d of age) were fed on a maize-soybean meal based (CS) diet with or without 20 g fish meal (FM)/kg and/or 10 g Gly/kg for 14 d. 2. Inflammatory responses were assessed by determining changes in the plasma concentrations of nitrate plus nitrite (NOx), caeruloplasmin (Cer) and -1 acid glycoprotein (AGP), and changes in the expression of mRNA encoding substances related to the inflammatory response, such as interleukin (IL)-1 and -6, tumour necrosis factor like ligand (TL)1A, inducible nitrite synthase (iNOS), interferon(IFN)-, following lipopolysaccharide (LPS) injection. 3. IL-1 and TL1A mRNA expression in chicks fed on the FM diet was higher than in chicks fed on the CS diet. 4. Supplementing the CS diet with Gly resulted in smaller increases in the plasma concentrations of NOx, Cer and AGP after LPS injection than were observed for chicks fed on the CS diet alone. In addition, 2 h after LPS challenge the expression of encoding inflammatory response-related substances was lower in the spleens of those chicks fed on the Gly-supplemented diet than in those fed the CS diet. 5. Supplementation of the FM diet with Gly reduced the plasma AGP concentration and IL-1 and TL1A expression. 6. These results suggest that modulation of inflammatory responses by dietary Gly supplementation is affected by dietary composition; Gly supplementation has different effects on the cytokine responses dependent on the diet.