Evaluation of Dietary Tryptophan Levels as a Restriction Method for Broiler Breeder Pullets123

ABSTRACT A total of 2,000 pullets and 300 cockerels from a broiler strain were started on experiment at two weeks of age. The following treatments were used: (1) 0.150 percent tryptophan and 28 mg. added niacin per kg. of diet; (2) 0.150 percent tryptophan and no added niacin in the diet; (3) 0.150 percent tryptophan with 28 mg. added niacin per kg. of diet; (4) 0.125 percent tryptophan with 28 mg. added niacin per kg. of diet; and (5) 0.100 percent tryptophan with 28 mg. added niacin per kg. of diet. Treatment 1 was limited daily, the others were ad libitum. Birds were maintained on these treatments until 22 weeks of age, at which time they were moved to a breeder house. During the breeder phase, the birds were subjected to either of two treatments; a constant protein level program or a two protein level phase feeding program. Body weights at 22 weeks of age were reduced by decreasing tryptophan levels. However, percent body fat increased with lower levels of tryptophan. Birds on low tryptophan levels consumed less feed per bird per day but feed efficiency was increased. Body weight increased greatly in Treatment 5 birds during the breeder phase. Hen day production and hen housed production were reduced in those previously fed the low levels of tryptophan. Hatch of total eggs set was also reduced by the lowest level of tryptophan; however, hatch of fertile eggs was not affected. Limited fed birds performed better overall in the breeder house than ad libitum fed birds