The presentstudy evaluated the influence of genotype and rearing system on the performanceof alternative lines of broiler chickens. Two experimental lines (Caipirinhaand 7P) and two commercial lines (Label Rouge and Paraíso Pedrês)were reared under intensive or semi-intensive (access to the pasture area after21 d of age) in an experiment with eight treatments, four replicates and 35birds per experimental unit. Corn-soybean meal based feed and water were offeredad libtum in the pen area only, and the chickens in the semi-intensivesystem had free access to the pasture area. The experiment was terminated wheneach pen reached 2300 g of average weight. Interaction line x system was detectedfor variable age at 2300 g (Age 2300) and average daily weight gain; the lineCaipirinha on the semi-intensive had Age 2300 increased (79.2 d vs. 73.3 d),while there was no difference for Label Rouge (84.0 d vs. 83.0 d), 7P (62.0d vs. 62.2 d) and Paraíso Pedrês (60.8 d vs. 61.0 d). Feed intake(5688 g) and feed conversion (2.46) for the Label Rouge broilers were differentfrom the others (feed intake from 4304 to 2996 g and feed conversion from 1.87to 2.17), and rearing system affect these variables. Mortality was not affectedby genetic lines or rearing system. The access to pasture in the semi-intensivesystem did not result in feed economy or improvement in the feed conversion,but resulted in reduction on the daily weight gain (as a consequence of dailyfeed intake) in the Caipirinha, probably because the birds stayed for a longerperiod of time in the pasture area.
