An experiment was conducted with 2,112 Ross male broiler chicks, with the objective to evaluate the use of non-nutrient additives (antibiotic, prebiotic and symbiotic) on performance and carcass characteristics of broilers. The birds were distributed in a complete randomized design in 2 × 6 (corn × additive) factorial arrangement, with 12 rations, eight replicates and 22 birds per experimental unit. Diets were based on corn and soybean meal, using in the half the rations standard quality corn (Rations 1 to 6) and the other half low quality corn (Rations 7 to 12). The rations were: 1 and 7, basal diet (BD); 2 and 8, BD + antibiotic; 3 and 9, BD + Symbiotic; 4 and 10, BD + prebiotic 1 (0.5 kg/t); 5 and 11, BD + prebiotic 1 (1.0 kg/t) and 6 and 12 BD + prebiotic 2 (1.0 kg/t). To increase the animal health challenge, beyond the reused bed, drinkers were not periodically cleaned, with the objective to decrease water quality. Average weight gain, feed intake and feed conversion ratio were evaluated at 21 and 42 days of age. At 23 days of age, the physical characteristic of liver and the presence of petechias in the breast and drumstick were determined, and at 42 days of age, the carcass characteristics and relative liver weight were also evaluated. Additive effect on average weight gain at 21days age, and on average weight gain and feed intake at 42 days age was observed. There was no additive effect on the others evaluated characteristics. The prebiotic based on mannanoligosaccharides and symbiotic can replace antibiotic avilamicin in broiler diets, therefore they had not promoted losses in the performance of the birds. The uses of low quality corn worse the animal performance, with decresaing yield and carcass quality of broiler chickens.
