With the objective of determine the nutritional requirement of lysine for growing white-egg and brown-egg laying hens in the period from 1 to 3 and 4 to 6 weeks of age, 480 birds were used in the period from 1 to 3 weeks of age and 432 birds in the period from 4 to 6 weeks of age. In both periods, Hy-line birds were used; 50% Hy-line W 36 (White) and 50% Hy-line Brown in completely randomized design in a 6 × 2 factorial arrangement (level of lysine [0.00, 0.06, 0.12, 0.18, 0.24, and 0.30%] and strains of laying hens). Based on the obtained results for the analyzed variable, the total lysine requirement for the period from 1 to 3 weeks of age was 1.052% for white birds and 0.981% brown birds or 207.38 mg of total lysine/day for white birds and 198.63 mg of total lysine/day for brown birds. For the period from 4 to 6 weeks of age the lysine requirement was 0.939% for white birds and 0.889% for brown birds or 323.30 mg of total lysine/day for white birds and 300.29 mg of total lysine/day for brown birds.
