Exigência de lisina e estimativa dos aminoácidos essenciais para tambaqui, Colossoma macropomum (CUVIER, 1818)ABSTRACT Four hundred-fifty (450) 7.7±0.06 g juvenile tambaqui were distributed in 500L boxes, fed a casein, gelatin and free amino acids-based semipurified diet containing six lysine levels (L-lysine HCL 0.9; 1.2; 1.5; 1.8; 2,1; 2.4% of the diet), in a completely randomized design, so that their lysine requirements could be determined. Findings demonstrated that diets with rising lysine levels did not influence the assessed zootechnical parameters.Tambaqui presented reduced consumption, low weight gains and high feed conversion with the use of the semipurified diet. This diet affected the hematological parameters significantly with no changes on total proteins and plasmatic glucose. The reduction on the plasmatic cortisol with the increase of lysine in the diet suggests the lower lysine levels to have had an influence on plasmatic cortisol level values. The reduced levels of triglycerides, cholesterol and body lipids with increasing lysine levels suggest a relationship of this amino acid with the accumulation of body lipids. Essencial amino acids demand estimated from tambaqui body amino acids content, showed to be similar to that found for other species and the lysine was estimated at dietary protein 6.0 and 6.2%, through the two utilized methods. The zootechnical performance exhibited by tambaqui, using semipurified diet for the lysine 0.9 to 2.4% interval in the diet did not allow its demand to be determined through dose-response method. RESUMOCom objetivo de determinar a exigência de lisina para o tambaqui, 450 juvenis (7,7±0,06 g) foram distribuídos em caixas de 500 litros, alimentados com dieta semipurificada à base de caseína, gelatina e aminoácidos livres, contendo seis níveis de lisina (L-lisina HCL 0,9; 1,2; 1,5; 1,8; 2,1; 2,4% da dieta), em delineamento inteiramente ao acaso. Os resultados demonstraram que as dietas com níveis crescentes de lisina não influenciaram os parâmetros zootécnicos avaliados. O tambaqui apresentou consumo reduzido, baixo ganho de peso e alta conversão alimentar com o uso de dieta semipurificada. Essa dieta afetou significativamente os parâmetros hematológicos e sem alterações nas proteínas totais e glicose plasmática. A diminuição no cortisol plasmático com o aumento de lisina na dieta sugere que níveis mais baixos de lisina influenciaram nos valores de cortisol plasmático. Os níveis reduzidos de triglicerídeos, colesterol e lipídios corporais com o aumento dos níveis de lisina sugerem uma relação deste aminoácido com o acúmulo de lipídios corporais. As exigências dos aminoácidos essenciais, estimados a partir do conteúdo de aminoácidos corporais do tambaqui, foram similares ao encontrados para outras espécies e a lisina foi estimada em 6,0 e 6,2% da proteína dietética pelos dois métodos utilizados. O desempenho zootécnico, apresentado pelo tambaqui, com uso de dieta semipurificada para o intervalo de 0,9 a 2,4% de lisina na dieta, não permitiu determinar a exigência ...

The present study evaluated practical diets with increasing levels of protein and energy on performance, fillet composition, feed cost, and physiological responses of pirarucu (Arapaima gigas) juveniles during the grow-out phase in a net cage system. In an on-farm trial for 90 days 225 pirarucu juveniles with initial weight ± standard deviation of 2025 ± 335 g were fed to apparent satiety with extruded diets containing 37.4 (T-37), 40.8 (T-40), 43.9 (T-43), 45.5 (T-46), and 47.1% (T-49) crude protein (CP), increasing lipid levels, and energy:protein ratio fixed in 10 kcal g-1. Protein and lipid concentrations in the diets influenced the cost, fillet composition, and important physiological aspects of the health maintenance and productive performance of the pirarucu juveniles. Fish fed the T-37 diet had lower concentrations of fat in body cavity, fillet and blood, and had a lower cost associated with feeding. The increase in protein and energy levels in the other diets tested reduced the economic return, did not improve the zootechnical performance and caused physiological changes in the fish.