ABSTRACT This study aimed to evaluate the yields of by-products and residues and the morphometry of juvenile tambaqui Colossoma macropomum undernutrition with different levels of lysine. Diets were elaborated containing 6.60, 9.72, 12.84, 15.96, 19.08, and 22.20 g kg−1 of total lysine, and these were fed to fish distributed in 18 tanks (310 L each one) for 90 days. Morphometric analysis, measurements of whole fish, by-products, and residues were taken and compared to each other. All variables were validated using ANOVA, Tukey's test, and quadratic regression analysis (P < 0.05). No differences were found for the morphometric variables (P > 0.05). The ratio between morphometric data for the standard and total length showed significance at levels of 9.72 and 15.96 g kg−1 (P = 0.03). The gutted fish and fillets, the protein and lipid contents of the fillets, and the weights and lengths of the intestines did not change (P > 0.05). Moisture was modified with lysine at levels of 22.20 g kg−1 (P = 0.00), and minerals, between 6.60 and 22.20 g kg−1 (P = 0.01). The increase in lysine levels in the diet led to an increase in fin weight (P = 0.00). It was concluded that the addition of lysine in the diet did not directly influence the morphometry and yields of the fish in the juvenile phase, but it did affect the fin waste and the skin by-product.

ABSTRACT This study aimed to evaluate the antioxidant potential of citric acid in plant protein based-diets offered to juvenile tambaqui, Colossoma macropomum. Four isonitrogenous and isoenergetic diets containing different levels of citric acid (0, 10, 20, and 30 g.kg−1) were formulated. Fish (n = 160; 27.56±1.03 g) were randomly distributed in 310-L water tanks (n = 16), with four replicates per treatment. After the experimental period (80 days), animals were anesthetized, and blood was collected for cell count. They were euthanized and dissected to remove livers for subsequent oxidative stress analyses. No significant differences were observed in the levels of thrombocytes, total leukocytes, lymphocytes, positive granular leukocytes, and immature leukocytes among the experimental treatments. However, there were fewer monocytes and neutrophils in fish fed the diet containing 30 g.kg−1 of citric acid. All citric acid diets increased glutathione concentration and reduced lipid peroxidation levels in livers. Therefore, citric acid acts as a potent antioxidant in juvenile tambaqui fed plant protein-based diets and, thus, can improve their maintenance conditions in production systems.

Resumo: O objetivo deste trabalho foi avaliar o coeficiente de digestibilidade aparente (CDA) de sorgo, e determinar o desempenho produtivo, os índices somáticos, os parâmetros hematológicos e a composição centesimal do filé de pacus alimentados com dietas com diferentes níveis de sorgo, além de avaliar o custo da formulação. Para a determinação do CDA da matéria seca (MS), da proteína bruta (PB), do extrato etéreo (EE) e da energia bruta (EB) do sorgo, utilizaram-se 160 pacus, com peso médio de 56,00±8,04 g, alimentados com dieta-referência e dieta-teste (30% sorgo), acrescidas de 0,1% de óxido de cromo III. Para avaliação do desempenho, utilizaram-se 180 juvenis de pacu (10,80±0,77 g) alimentados com cinco dietas experimentais, em que 0, 25, 50, 75 e 100% da energia do milho foi substituída pela do sorgo. Os CDA do sorgo pelo pacu foram: 78,52% da MS; 74,82% da PB; 94,36% de EE; e 77,24% de EB. Não se observaram diferenças entre as dietas quanto ao desempenho, aos índices somáticos e aos parâmetros hematológicos. Porém, na composição centesimal dos filés, houve diferença entre os tratamentos. O sorgo apresenta CDA semelhante ao do milho e pode substituí-lo integralmente em dietas para juvenis de pacu, além de diminuir o custo da formulação.

Abstract: The objective of this work was to evaluate the apparent digestibility coefficient (ADC) of sorghum, and to determine the growth performance, somatic indices, hematological parameters, and fillet centesimal composition of pacu juveniles fed diets with different levels of sorghum, besides evaluating the cost of the diet formulation. To determine the ADC of dry matter (DM), crude protein (CP), ether extracts (EE), and gross energy (GE) of sorghum, 160 pacus, with 56.00±8.04 g average weight, were used; fish were fed reference and test diets (30% sorghum) plus 0.1% of chromium III oxide. For the growth performance trial, 180 juvenile pacu (10.80±0.77 g) were used; fish were fed diets containing 0, 25, 50, 75, and 100% replacement of corn by sorghum. The ADC of sorghum by fish were: 78.52% of DM; 74.82% of CP; 94.36% of EE; and 77.24% of GE. There were no differences among diets for the growth performance variables, somatic rates, and hematological parameters. However, for the centesimal composition of fillets, there were differences among treatments. Sorghum shows ADC similar to those of corn and can totally replace it in pacu juvenile diets, besides reducing formulation costs.