Threonine requirement of commercial laying hens fed a corn-soybean meal diet

Two experiments were conducted with Hy-Line W36 hens to evaluate their Thr requirement in a corn-soybean meal diet. Eight experimental diets were used in Experiment I with graded levels of Thr: 0.53, 0.50, 0.48, 0.45, 0.42, 0.40, 0.37, and 0.35%. Seven experimental diets were used in Experiment 2 with graded levels of Thr: 0.58, 0.53, 0.50, 0.48, 0.45, 0.42, and 0.40%. Supplemental amino acids (AA) were added to all diets to ensure that Thr was the first-limiting AA. Egg production (EP), egg mass (EM), and daily Thr intake were significantly increased with increasing dietary Thr levels. Broken-line regression indicated a daily Thr requirement of 439.0 and 462.1 mg per hen per d in Experiment 1 and of 393.9 and 447.1 mg per hen per d in Experiment 2 for EP and EM, respectively. The Thr requirements to produce 1 g of EM were 8.76 and 9.44 mg in Experiments 1 and 2, respectively.