No abstract

Symphysodon aequifasciatus is a fish with a disk-shaped body and bright colors, important characteristics of ornamental fish. We evaluated amino acid supplementation strategies to reduce crude protein in the diet for evaluation of performance, the content of digestive enzymes, liver metabolism, and intestinal histopathology. A total of 180 fish were randomly distributed in 12 separate 50 L glass aquariums, consisting of a completely randomized design with four treatments (DC - Control diet with 34.4% crude protein; DL - Control diet plus 1% of lysine; DEAA - Control diet plus 1% free essential amino acids (threonine, phenylalanine, leucine, valine, arginine, and tryptophan); and DHP - Diet with a high level of crude protein 48.4%), three repetitions, lasting 60 days. The use of DL and DEAA diets resulted in higher intestinal villus height and higher zootechnical performance. The use of DL diet increased alkaline phosphatase and digestive amylase activity. The use of DHP diets promotes severe liver changes due to increased activity of Alanine aminotraserase. Therefore, it was possible to observe that the use of amino acids can supply the nutritional need of blue discus. Supplementation of diets with AAs allows the reduction of dietary protein, which is a strategy for feeding management.

In this study was evaluated the hematological response of ornamental Amazon plecos Cochliodon sp. (L145) and Hypostomus sp. (L28) submitted to transportation conditions. The erythrogram, leukogram, thrombogram, glucose and total plasma proteins (PPT) were determined at 0, 6, 24, 48 and 72 hours after 3-hours simulated transportation. For basal hematological profile, the blood was collected immediately to allow comparisons after the transport stress. Cochliodon sp. showed reduction in total erythrocyte after 6 and 24 hours of post-transport, and increase after 6 hours. Hypoglycemia were observed at 6 hours post-transport for Hypostomus sp. Thus, the Hypostomus sp. showed higher resistance compared to Cochliodon sp. when to the transport stress.

The selection of ingredients is an important aspect for diets formulation for fish in captivity. The use of fruit industry by-products can be an alternative for inclusion in diets for ornamental fish, as discus fish case, to improve health and reduction of production costs, further to reducing the environmental impacts of fruits industries residues. The objective the studies was to evaluate the bioavailability of fruit industry by-products in the diet for discus fish by coefficients of digestibility. The digestibility of three by-products: pineapple by-product, mango by-product, and passion fruit by-product were evaluated. Thirty-two discus fish (106 ± 26.6 g) were distributed in 4 tanks for feeding and fecal collection, constituting an experimental design in Latin square (4 diets test- x 4 periods of fecal collection x 4 replicates). The three by-products had digestibility coefficients above 80%, 70%, and 69% for dry matter, protein, and fat, respectively, being possible to use them as a source of these nutrients in diets for the discus fish. However, it was observed that the mango and passion fruit by-product had the lowest energy digestibility coefficient, with bioavailabilities less than 50% of utilization. The co-products of the fruit processing industry tested in this work have nutritional conditions to be used as food for root discs. The use of these co-products as food for ornamental fish can be an alternative use and value.

The aim of this study was to evaluate the chronic salinity tolerance of Carassius auratus and the effects on blood parameters, gill morphology, and survival. In the first test, nine different concentrations (0.0, 0.5, 1.0, 2.5, 5.0, 10, 15, 20, and 25 g L-1) of NaCl were used with nine repetitions for 96 h. The survival of fish subjected to 15 g L-1 NaCl was 4 h, and 5 min at a concentration of 25 g L-1. The mortality of fish with 15 g L-1 NaCl was 100%. Morphological analyses of the gills showed hyperplasia of the coated cells in the interlamellar space and hypersecretion of mucus in fish exposed to 10 g L-1 of NaCl. At concentrations of 20 and 25 g L-1, necrosis of the support collagen caused the cells to detach from the lamellar structure mucosa. In the chronic test, two concentrations were used, with four replications containing nine fish in each aquarium for a period of 21 days. Blood samples and gills from the fish were collected, and it was observed that the fish showed a decrease in the concentration of bicarbonate (NaHCO3) in the blood, indicating hypernatremia. Acute exposure of C. auratus to sodium chloride (NaCl) should be at a maximum of 10 g L-1 of NaCl, after which level there would be a loss in animal performance and/or mortality. Chronic exposure to 5 g L-1 of NaCl promotes acidemia, ionic imbalance, and pathological changes in the gills; therefore, it is not recommended.