The aim of the current study was to evaluate the performance of experimental and commercial genotypes of chicken recommended for free-range rearing system submitted to two diet programs (conventional and alternative). The experimental design consisted of a randomized design applied until 28 days and a randomized factorial 8x2 design (eight genotypes: Paraíso Pedrês, Caipirão da ESALQ, 7 P, Embrapa 041, Label Rouge, Paraíso Pelado, Caipirinha da ESALQ and Carijó Barbada and two diet programs), using two replicates with 30 chickens/box as experimental unit, from 29 to 84 days of age. Average body weight and feed:gain ratio were recorded during three periods: 1) 0-28, 2) 0-56 and 3) 0-84 days and submitted to the analysis of variance. The effect of diet was evidenced for all traits in periods 2 and 3. The effect of genotype was verified for all variables in period 1, but only for average body weight in periods 2 and 3. The interaction genotype and diet was observed for feed:gain ratio in period 2 and for all traits in period 3. Paraíso Pedrês and Caipirão from ESALQ presented higher average body weight than the other genotypes in period 1. In period 2, Paraíso Pedrês presented the highest average body weight and all genotypes differed for feed:gain ratio. Caipirão from ESALQ, Paraíso Pedrês and 7 P presented higher average body weight than the other genotypes and all strains differed for feed:gain ratio in period 3. The full substitution of conventional diet by corn led to a worse chicken performance. Overall performance of the evaluated genotypes was conditioned by genetic and nutrition factors, with the lowest negative effects of substitution of conventional diet by corn on all traits in the Paraíso Pedrês genotype.
nutrition; performance; poultry breeding; production system
