One experiment was carried out using 120 laying Isa Brown chickens fed diets containing sugar-cane yeast, to determinate the methionine+cystine (met+cys) requirements. The birds were 51 weeks old at the beginning of the experiment, with the duration of 84 days, with three periods of 28 days each. A completely randomized block design with five treatments and four replications was used. The treatments consisted of a basal diet supplemented with five levels of DL-methionine in order to obtain diets with 0.45, 0.50, 0.55, 0.60, and 0.65% of met+cys. The basal diet with 13%CP and 2840 kcal EM/kg was composed by corn, soy bean meal and sugar-cane yeast. Referring variables were analyzed to the productive performance (production of eggs, weight gain, feed consumption and conversion) and quality of the eggs (weigh, mass and content of eggs and Haugh Units). A quadratic effect of the met+cys levels was observed on the appraised characteristics, except for the weight gain that was not influenced by the treatments. Working with regression models, it was possible the determination of the best met+cys levels. For greater egg production and ration consumption, the requirements were .565 and .569% of met+cys, respectively. For egg weight and egg mass the use of .582% and .569% of met+cys, allowed to obtain the better results, respectively.
requirement; productive performance; laying hens; quality of egg; methionine+cystine
