Lysine and threonine responses in Ross TP16 male broilers

Today's economy requires minimal feed cost for poultry producers to maintain a profit. Two experiments were performed to evaluate Lys (2 levels) and Thr (4 levels) factorial responses in Ross TP16 (Test Product 16) high-yielding male broilers from 14 to 28 d and 28 to 42 d of age. From 14 to 28 d (experiment 1), digestible Lys was fed at 1.12 and 1.18% of the diet. The basal diets contained digestible Thr at 0.69, 0.73, 0.77, and 0.81% of the diet, and L-Thr was added to achieve supplemented Thr diets. From 28 to 42 d (experiment 2), the basal test diet contained 1.00% digestible Lys and 0.60% digestible Thr. Additions of crystalline Lys and Thr yielded additional digestible levels of Lys (1.05% of diet) and Thr (0.64, 0.68, and 0.72% of diet). Live performance measurements in experiment 1 did not differ among treatments. In experiment 2, increasing Lys and Thr in the diet improved some live performance parameters, but 1.05% Lys may have been too high to estimate a Thr-to-Lys ratio, as indicated by significant BW gain and feed intake interactions. We conclude, based on the 28- to 42-d interactions, that a Thr-to-Lys ratio of 68 supports adequate growth in birds fed the 1.00% digestible Lys.