Effect of Stocking Density on Growth Performance and Carcass Characteristics of Broilers Grown to 3 Kg under Antibiotic Free Diets1,2

Background: Stocking densities could have a significant impact on birds when reducing or eliminating antimicrobials (antibiotic-free; ABF) in poultry diets. This study investigated the effects of stocking densities on growth performance and carcass characteristics of broilers fed antibiotic-free diets grown to 3 kg. Methods: A total of 888 1-d-old Ross x Ross 708 chicks were randomly distributed into 24 pens. The treatments were four stocking densities including 29, 33, 39 and 42 kg of BW/m(2); each treatment was represented by six replicates. Treatments were blocked within the room to account for any variations in room conditions. Treatment assignments were randomized within each block. Used bedding was obtained from commercial farms to simulate commercial conditions and litter microflora. Birds were fed antibiotic-free (ABF) diets and provided a three phase-feeding program (Starter: 0-14 d, Grower: 15-28 d and Finisher: 29-42 d). Feed and water were provided ad libitum. Birds and feed were weighed on 1, 14, 28 and 42 d of age to measure growth performance. On d 43, 10 (5 males and 5 females) birds from each pen were processed to determine weights and yields. Result: The BW and BW gain, live weight, carcass weights and carcass yield percentage were not affected by stocking density. Also, mortality was not affected by stocking density. However, FI and FCR for the starter period were significantly elevated (P<0.001 and P<0.001, respectively) at lower stocking densities, but were not different for the remainder of the growout. In conclusion, stocking densities evaluated from 29 to 42 kg/m(2) with appropriate environmental management has a negligible effect on overall production and processing yield in ABF broilers.