Digestible protein requirement of Amazonian pintado (Pseudoplatystoma reticulatum × Leiarius marmoratus)

This study was undertaken to determine the digestible protein requirement of Amazonian pintado (Pseudoplatystoma reticulatum × Leiarius marmoratus) during growing phase (290–650 g), and the impact of digestible protein levels to body yield, fillet quality, total ammonia excretion rate, and meat chemical composition. Seven digestible protein levels diets were evaluated, 225, 250, 275, 300, 325, 350, or 375 g kg⁻¹. The experiment was carried out in a completely randomized design with seven treatments (digestible protein levels) and five replicates. The experiment lasted for 72 days. Production performance did not differ between treatments, except for protein efficiency rate, which was highest (P < 0.05) in the fish that received the diet with the lowest digestible protein content. Digestible protein levels above 325 g kg⁻¹ allowed less (P < 0.05) fat accumulation in the carcass. Ammonia excretion rate fitted a quadratic model (P < 0.05). According to the model used, the minimum ammonia excretion value was 0.06225 µg L⁻¹ g⁻¹, corresponding to a digestible protein input of 255 g kg⁻¹. The average fillet color (b*) value was higher (P < 0.05) (15.4) in the group fed 250 g kg⁻¹ digestible protein than in the fish fed 350 g kg⁻¹ digestible protein, whereas the other groups showed intermediate results. Fillet pH, shear force, drip loss, and cooking loss did not differ (P > 0.05) between the digestible protein levels. Digestible protein levels above 325 g kg⁻¹ allowed less fat accumulation in the carcass. Based on the ammonia excretion model, it was recommended 255 g kg⁻¹ of digestible protein level in diets to Amazonian pintado in growing phase.