This study was conducted to evaluate broiler growth performance and body fraction weights , in response to increasing levels of dietary digestible lysine (dig Lys) (0.70, 0.80, 0.90, 1.00, 1.055, 1.11, 1.165 and 1.22%). Three hundred and twenty male broilers CobbXCobb500 were used from 19 to 40 days of age. Two basal diets were used with 19 and 20.5% of crude protein. The first basal diet was set for the four lower levels of dig Lys, and the second for the other four levels. The diets were formulated to maintain in a constant ratio the digestible Met, Arg and Tre with the dig. Lys. Body weight, weight gain, feed intake, Lys intake and feed conversion were evaluated at 26, 33 and 40 days of age. At these same ages body weight fractions as carcass, breast, thigh, leg, back+wing+thigh wing+head+neck (D+A), viscera+blood and feathers were evaluated:. Weight gain and feed conversion increased positively and linearly with the increasing dig Lys. In other hand, feed intake was not influenced by treatments. Breast and carcass fractions increased linearly in all evaluated periods (26, 33 and 40 days of age), with the best estimated level of dig Lys ≥1.22%. The same response was seem for thigh at 26 and 40 days, for D+A at 33 and 40 days, for leg at 26 and 33 and a quadratic response was observed for leg at 40 days, although the best estimated level of dig Lys was equal or higher than 1.22%. It is suggested more studies with higher levels of dig Lys in Cobb 500 male broiler chicken diets.
amino acids; carcass; commercial cut; poultry; protein
