Dietary vitamin supplementation decrease stress caused by high stocking density, and boosts immunological system of farmed fish. A studied was carried out to determine vitamin A requirements of Nile tilapia (Oreochromis niloticus) in an all male group (13.8 ± 1.2 g) and a mixed sex population (9.8 ± 2.3 g). Fish stocked in 100-L plastic aquaria (26.0 ± 1.0ºC) were fed to near satiety, twice a day, seven days a week, during 75 days with vitamin A-free, semi-purified diets supplemented with 0; 600; 1,200; 1,800; 2,400; 3,000; 3,600; 4,200; 4,800 and 5,400 International Units (IU) of retinyl palmitate (30% vitamin A) per kg of diet in a completely randomized experimental design, factorial arrangement 2χ10 (n = 4). Deficiency signs of vitamin A were observed in fish fed 0 to 1.200 IU vitamin A kg -1 diet; moderate signs were observed in fish fed diets with 1.800 to 3.600 IU vitamin A kg -1 diet; no interactions group*level (p < 0.05) were detected. Dietary levels of vitamin A up to 5.400 IU kg -1 influenced final weight and weight gain of fish (p < 0.05), but did not influence feed consumption (p > 0.05). A group effect was observed regarding all performance variables (p < 0.0001). Quantification of hepatic retinol (HPLC) detected vitamin A only in fish fed 5.400 IU retinol kg -1 of diet, therefore characterizing that dietary retinol was used and stored. The quantity of 5.400 IU of retinol kg -1 of diet is recommended for adequate nutrition of Nile tilapia.

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Studies investigating improved protein:lipid ratios based on their effects on growth, nutrient utilization, digestive enzyme activities, blood metabolites and erythogram in tropical carnivorous fish are very scarce. This study evaluated the effect of different protein:lipid ratios on these parameters in the hybrid surubim Pseudoplatystoma corruscans × Leiarius marmoratus. Juvenile fish (8.90 ± 0.94 g initial weight) were fed 3% of total biomass for 60 days using four isoenergetic experimental diets with different protein:lipid ratios (9.00, 4.60, 3.54 and 1.78). Higher growth performance parameters were observed at higher protein:lipid ratios. The activities of intestine total alkaline protease, trypsin and lipase (U/mg protein) were not affected by dietary treatments. Chymotrypsin (U/mg protein) was higher in the 4.60 protein:lipid ratio group. Amylase (U/mg protein) was higher in intermediate groups. Blood glucose, total plasma protein, triglycerides, cholesterol and free amino acids decreased as the protein:lipid ratio decreased. Haematocrit was higher at the 9.00 and 4.60 protein:lipid ratios. Hybrid surubim showed metabolic adaptation to the different protein:lipid ratios tested. These results suggest that the 4.60 protein:lipid ratio showed the best protein‐sparing effect of lipids.

A farinha de manga com cascas foi avaliada como fonte de carboidrato em substituição ao milho para o crescimento de alevinos de tilápia e composição química da carcaça. Foram utilizados 180 peixes (4,69 ± 0,06 g) estocados em 12 caixas de 500 L, alimentados três vezes ao dia (6 % peso vivo), em um sistema de recirculação de água com biofiltro. Foram testadas quatro dietas com diferentes concentrações de farinha de manga T1= dieta com 30 % de milho; T2= 33 % substituição milho por manga; T3= 66 % substituição milho por manga e T4= 100 % de substituição do milho pela manga com três repetições. Ao final de 45 dias, foram avaliados o desempenho zootécnico (peso médio final, ganho de peso médio final, taxa de crescimento específico, consumo de ração aparente, conversão alimentar aparente, rendimento de carcaça, sobrevivência) e composição química da carcaça. Os níveis de farinha de manga em substituição ao milho afetaram todas as variáveis de desempenho a partir de 33 % de substituição (p<0,05), com exceção da sobrevivência e o rendimento de carcaça (p>0,05). Os valores da composição química da carcaça foram alterados com exceção da matéria mineral. A farinha de manga em substituição ao milho pode ser utilizada em até 33 % na ração da tilápia do Nilo sem prejudicar o desempenho zootécnico e a composição química da carcaça.

PALAVRAS CHAVE ADICIONAIS SUMMARYThe study evaluated tambaqui, Colossoma macropomum, performance fed different levels of mango (Mangifera indica) meal in the feed (20, 30, 40 and 50 %) and the reduction of protein levels (38, 33, 28 and 23 %). To this study, 240 fish were used, separated in 12 equal groups, in four treatments and three replications in a randomized system. Initial weight was 5,21; 5,24; 5,19 and 4,99 g respectively. The trial lasted 56 days and fish were periodically weight. Fish were fed daily ad libitum. The following performance parameters were analyzed: specific growth, biomass gain; apparent fed conversion, survival, metabolic profile and digestives enzymes activity. All data show positive polynomial regression for the diet with 50 % mango meal and 23 % protein (R50). Performance parameters had a significant effect with higher results in the groups were mango meal was higher and protein level was lower. Final average weigh was R20: 8,65; R30: 8,81; R40: 8,68 and R50: 11,39 g. From metabolic profile analyzes: glucose, hepatic glycogen, total amino acids and cholesterol it was observed that there are a mobilization from these metabolites in order to keep energy process for tambaqui growth. It was concluded that the best tambaqui performance occured in the diet with 50 % of mango meal inclusion and 23 % of protein. Fish metabolic profile is positively affected by the replacement of protein by mango meal.