Effects of Supplemental Zinc in a Wheat-Based Diet on Performance, Intestinal Viscosity, Immune System and Lipid Peroxidation of 21-Day Old Broiler Chickens

We investigated the effects of a wheat-based diet (WBD) supplemented with different levels of zinc on the performance, intestinal viscosity, immune system and lipid peroxidation of broiler chickens. A total of 240 Ross 308 day-old male broiler chicks were weighed and assigned to six dietary treatments with four replicates (floor pens) of ten birds per pen. Dietary treatments consisted of a WBD without Zn supplement in mineral premix (control), or with 20, 40, 60, 80, and 100 mg/kg of Zn in the diet. Feed intake, body weight gain, and feed conversion ratio were recorded after 21 days. On day 21, blood serum malondialdehyde concentration, intestinal digesta viscosity, and some internal organs were measured. Antibody titer against Sheep red blood cells (SRBC) were measured on days 7 and 14 after injection. For evaluation of cutaneous basophil hypersensitivity (CBH) response, on d 20, phytohemagglutinin was injected subcutaneously into toe web and 12 and 24 hrs after injection, the thickness of the web was measured. Supplementation of the WBD with 20, 40, 60, and 80 mg Zn/kg significantly improved feed conversion ratio (P < 0.05). Supplementation of Zn significantly decreased the relative weight of abdominal fat pad as well as jejunal viscosity (P < 0.05). Also, Zn supplementation (at all concentrations except 20 mg/kg) significantly decreased serum malondialdehyde concentration (P< 0.05). Anti-SRBC titer was significantly increased by supplementation of the WBD with 20 mg/kg Zn (P < 0.05). Supplementation of the WBD with 40 mg/kg Zn significantly increased CBH response (P < 0.05). Overall, the results of this study indicate the importance of Zn supplementation in WBD for improvement of FCR and physicochemical properties of the intestinal contents. Also, supplementation of Zn in the WBD is effective in enhancing immune system responses and antioxidative defense.