The present study evaluated the influence of genotype and rearing system on the performance of alternative lines of broiler chickens. Two experimental lines (Caipirinha and 7P) and two commercial lines (Label Rouge and Paraíso Pedrês) were reared under intensive or semi-intensive (access to the pasture area after 21 d of age) in an experiment with eight treatments, four replicates and 35 birds per experimental unit. Corn-soybean meal based feed and water were offered ad libtum in the pen area only, and the chickens in the semi-intensive system had free access to the pasture area. The experiment was terminated when each pen reached 2300 g of average weight. Interaction line x system was detected for variable age at 2300 g (Age 2300) and average daily weight gain; the line Caipirinha 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 (62.0 d 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 different from the others (feed intake from 4304 to 2996 g and feed conversion from 1.87 to 2.17), and rearing system affect these variables. Mortality was not affected by genetic lines or rearing system. The access to pasture in the semi-intensive system 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 daily feed intake) in the Caipirinha, probably because the birds stayed for a longer period of time in the pasture area.
alternative lines of broiler chicken; performance; rearing system
