The objective of this study was designed to test whether supplementation of the diet with arginine (Arg) or glutamine (Gln) or their combination influences the production, organ weights and humoral immune response of broilers. A total of 432 one-day-old male Ross 308 broiler chickens were divided into 6 treatment groups: control, Arg-0.5%, Arg-1%, Gln-0.5%, Gln-1% and Arg-0.5%+Gln-0.5%. Drinking water and feed were provided ad libitum. On day 18 of the experiment 50% of chickens in each treatment group were immunised with bovine serum albumin. Ten and 21 days after immunisation blood samples were collected to determine the anti-albumin IgY titre, interleukin 6 (IL6) and interferon gamma (IFNG) and to measure the weight of the liver, spleen, bursa of Fabricius and thymus. Arg or Gln supplementation of the diets influenced neither the production nor the organ weights until 18 days of age. Between 18 and 39 days of age both Arg (0.5% and 1%) and Arg + Gln supplementation improved the feed conversion ratio (FCR) by 3.7%, 6.3% and 4.9%, respectively, while Gln-1% worsened it by 15%. Immunisation slightly (-0.79%) depressed the body weight gain of broilers fed the control diet, which was significantly improved by both Arg (0.5 or 1%) and Arg + Gln supplementation. Immunisation increased the weight of the spleen, bursa and thymus and decreased that of the liver. Supplementation with 1% Gln depressed (-5.13%) the body weight gain of the immunised chickens but strongly stimulated the immune response. Supplementations with Arg and Gln did not influence the IL6 and IFNG level of the blood; however, on day 10 after immunisation these two parameters showed a negative correlation with each other. Regarding production, organ weights and immunity, Arg supplementation should be recommended in the grower phase, while Gln supplementation can be useful in pullets raised for egg production, where a good immune response to vaccinations is an important factor.
Arginine; IFNG; IL6; antibody titre; broilers; glutamine; organ weights