Two trials were conducted to determine the requirement of methionine + cistyne for Ross female broilers from 1 to 21 and 22 to 42 days old on tropical climate region. The following parameters were evaluated: feed intake, weight gain, feed: gain ratio, absolute weights and yields of noble cuts (breast, thighs and drumsticks) and abdominal fat. The experiment was analyzed as a complete randomized design with six levels of methionine + cystineand four replicates of 12 birds per replicate, in a total of 288 birds for each experiment. The diets were formulated to meet the bird nutricional requirements, except for methionine + cystine levels. The diets were supplemented with DL-methionine at levels of 0, 0.08, 0.16, 0.24, 0.32, and 0.40% to contain 0.69, 0.77, 0.85, 0.93, 1.01, and 1.09% of methionine + cystine, for the period from 1 to 21 days and 0.61; 0.69; 0.77; 0.85; 0.93 and 1,01% of methionine + cystine, for the period from 22 to 42 days old. Quadractic effect of levels of methionine + cistyne on weight gain and feed: gain ratio, from 1 to 21 days old, and linear effect on weight gain, feed: gain ratio, absolute weights of abdominal fat, carcass, breast, thighs, and drumsticks and yields of carcass and abdominal fat, from 22 to 42 days old, were observed. According to the performance data, the nutritional requirements of methionine + cystine for female Ross broilers were estimated in 0.96%, for the periods from 1 to 21 and 22 to 42 days old.
broiler; methionine + cystine; nutritional requirement
