Tryptophan requirements and recovery performance pattern of commercial laying hens after feeding tryptophan-deficient diets

This experiment was carried out to evaluate the tryptophan (Trp) requirements and the recovery performance pattern of laying hens fed Trp-deficient diets. One hundred sixty Hisex White commercial laying hens were randomly distributed in five Trp levels in the diets (0.13, 0.15, 0.17, 0.19 and 0.21%) with eight replicates of four birds. The laying hens remained for two weeks in adaptation ( 51 to 52 weeks), for six weeks for evaluation of Trp requirements ( 53 to 58 weeks) and for four weeks for the determination of the recovery performance pattern ( 59 to 62 weeks). Egg production and egg mass were impaired when laying hens were fed diets containing 0.13% of Trp, however, the performance was recovered after one week of feeding under a diet containing 0.21% of this amino acid. Internal egg quality was not influenced by the Trp levels studied ( intake among 137.1 to 228.0 of Trp mg/day). Tryptophan requirements ranged from 161 to 188 mg/ay, depending on the characteristics evaluated ( egg production or egg mass) and the regression model applied ( polynomial, exponential or broken line).