Conversion of tryptophan into niacin in the turkey (Meleagris gallipavos)

Using Nicholas Large White turkey poults from 1 to 21 days of age, two experiments were conducted to measure the conversion of tryptophan into niacin. In Experiment 1, the dietary treatments were 0, 6, and 12 mg of supplemental niacin and 0, 150, 300, 450, and 1,000 mg of supplemental L-tryptophan per kg of diet, respectively. In Experiment 2, the niacin treatments were the same as in Experiment 1, but the L-tryptophan levels were 0, 150, 300, 450, 600, 800, 1,000, and 1,500 mg per kg, respectively. In both experiments, the diets used were based on corn and soybean meal. By analysis, the basal diet contained 29.6% crude protein, .35% tryptophan, 23 mg per kg of niacin, and 4.7 mg per kg of pyridoxine. Using Finney's slope ratio procedure, conversions were obtained of 103:1 (tryptophan:niacin) and 119:1 for Experiments 1 and 2, respectively. These results indicated the consistent, although inefficient, role of tryptophan as niacin precursor in turkeys fed a practical diet, compared with the reported conversion in other species.