The inclusion of different percentages of digestible lysine in low-protein diets was evaluated for male and female free-range broiler chickens, from 1 to 28 days. We used 792 female and 792 male naked neck chickens a day in a completely randomized 2x6 factorial scheme (sex x percentages of digestible lysine: 0.85, 0.90, 0.95, 1.00, 1.05 and1.10%) with six replicates of 22 broilers. No interaction of sex versus lysine was found. Superiority was observed (P<0.05) in males compared to females for all variables.Weight gainof chickens decreased linearly(P<0.05) with increasing levels of digestible lysine in the diet. There was a linear reduction (P<0.01) in feed intake, protein and metabolizable energy. On the other hand, the consumption of digestible lysine increased linearly (P<0.01) with the increase of its concentration in the diet. There was nodifference (P>0.05) in food conversion.In the chemical composition of the carcass, only thepercentage of mineral matter was influenced (P<0.05) bydigestible lysine levels.It was concluded that the level of 0.85% for type redneck broiler meets the nutritional requirement of digestible lysine in diets containing lower protein concentrations.
amino acids; broiler; carcass; performance; semi-intensive system