Effects of different dietary sources and levels of selenium supplements on growth performance, antioxidant status and immune parameters in Ross 308 broiler chickens.

1. Although different impacts of various sources of selenium (Se) on chicken performance have been largely studied, there is a lack of comparative experiments studying the effects of these sources on the immune system and antioxidant indices of broiler tissues. The aim of this study was to examine the effects of various sources and levels of dietary Se supplements on performance, antioxidant status and immune parameters in Ross 308 broiler chickens. 2. A total of 1200 1-d-old male broilers (Ross × Ross 308) were divided into 8 treatments with 6 replicate pens and 25 birds per pen. This experiment was conducted as a completely randomised design with a 4 × 2 factorial arrangement. Main factors included Se sources as sodium selenite (SS), Se-enriched yeast (SY), DL-selenomethionine (SM) and nano-selenium (NS) and levels at 0.1 or 0.4 mg/kg Se. 3. Dietary supplementation of organic Se sources significantly improved average daily gain (ADG), gain: feed ratio and European production efficiency factor (P < 0.05) compared to birds fed on diets supplemented with inorganic source. In addition, ADG was increased in response to increased level of supplemental Se. Based on contrast comparison, there were significant differences in these parameters between organic versus inorganic sources of Se. However, there was no difference between contrast comparisons of NS versus SM and SY. 4. Total anti-sheep red blood cell (SRBC) and Immunoglobulin G (IgG) titres and hypersensitivity were enhanced by increasing supplemental concentration of Se and using organic sources of Se rather than SS (P < 0.05). 5. Oxidation resistance assessment of tissues demonstrated that supplementation of organic sources of Se and increase in supplemental concentration of Se ameliorated glutathione peroxidase activity, total antioxidant capacity and malondialdehyde formation (P < 0.05). Mostly, there were significant differences between organic versus inorganic sources of Se in oxidation resistance. 6. Overall, dietary supplementation of 0.4 mg/kg Se from an organic source resulted in better production performance and immune system response. Moreover, minimum formation of malondialdehyde in broiler tissue was observed in birds fed on diets supplemented with SM at 0.4 mg/kg. 7. It can be concluded that SM is more effective than other sources of Se in reducing lipid oxidation.