Nutritional requirement of digestible tryptophan for white-egg layers of 60 to 76 weeks of age

The objective of this study was to determine the nutritional requirement of digestible Trp for white egg layers in the period from 60 to 76 wk of age. A total of 180 Dekalb White layers with an average weight of 1,345 kg were distributed in a completely randomized design with 5 increasing levels of digestible Trp (0.167, 0.175, 0.183, 0.191, and 0.199%), 6 replicates, and 6 birds per experimental unit. The diets of the treatments contained 0.759% of digestible Lys, which was obtained using the prediction equation of the Brazilian Tables for Poultry and Swine, and each treatment consisted of a digestible Trp-to-Lys ratio of 22, 23, 24, 25, or 26%. The digestible Trp levels in the diet had a quadratic effect on egg production, egg mass, and conversion per mass and per dozen eggs, and a linear effect on egg weight. In conclusion, a diet with 0.192% digestible Trp, in a 25.33% ratio with digestible Lys or 212 mg/bird per day, can be recommended for white egg layers of 60 to 76 wk of age.