Tryptophan intake for maintenance of Japanese quail

Tryptophan (TRP) is a precursor of the synthesis of melatonin and may reduces aggressive behavior in quails, which unquestionably facilitates their daily handling and somehow contributes to a more efficient egg production. Thus, the aim of this study was to determine TRP maintenance requirement for Japanese quails. Three hundred ninety-two Japanese quails were distributed in a completely randomized design with eight treatments (TRP levels) and seven replications of seven birds per experimental unit. The experimental diets were formulated by dilution technique. Two diets were formulated: one summit diet with high protein content and another protein-free diet. These two diets were mixed in suitable proportions to obtain the levels of digestible tryptophan (0.069; 0.100; 0.138; 0.180; 0.213; 0.245 and 0.276%). A control diet (adding 0.013 g L-Tryptophan/kg in the diet with the lowest TRP level) was added to confirm that the responses were due to the TRP limitation. The maintenance requirement of TRP was obtained by exponential relationship between TRP intake and egg output using the monomolecular function: Y=ax[1-e^-bx(X-m)], where Y is the egg output (g/BW_kg^0.75 per day); X is the TRP intake (mg/BW_kg^0.75 per day); a is the maximum response for egg output (g/BW_kg^0.75 per day); b is the slope of the function; and m is the maintenance requirement (mg/BW_kg^0.75 per day). The maximum egg output (a) and b were estimated at 41g / BW_kg^0.75 per day and 0.0144, respectively. The TRP requirement for maintenance was obtained by calculating the monomolecular function for Y=0. Thus, the TRP requirement for maintenance was estimated as 47 mg/BW_kg^0.75 per day. The estimated TRP maintenance requirement of 47 mg/BW_kg^0.75 per day for Japanese quails is almost three times of TRP maintenance requirement found in the literature for other adult birds, leading to conclude that quails have a higher metabolic demand for tryptophan to maintain the body and egg mass production and this must be considered in quail?s nutrition.