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The objective of this work was to evaluate different feeding rates on the productive performance of cobia (Rachycentron canadum) grown in brackish waters. For the experiment, 1,600 juveniles were distributed in 16 enclosures installed in an estuarine pond. Four different feeding rates were evaluated: 1, 3, 5, and 7% live weight (LW) per day. The following performance parameters were assessed: survival, final biomass, specific growth rate, daily weight gain, apparent feed conversion, protein efficiency rate, lipid efficiency rate, and hepatosomatic index. Survival was greater than 80% at all feeding rates. The most efficient feed conversion rate was obtained with the feeding rate of 5% LW per day, which also resulted in better values for the hepatosomatic index. The rate of 5% LW per day provides a better productive performance for cobia in brackish waters. Resumo: O objetivo deste trabalho foi avaliar diferentes taxas de arraçoamento no desempenho produtivo de bijupirá (Rachycentron canadum) criado em águas salobras. Para o experimento, 1.600 juvenis foram distribuídos em 16 cercados instalados em viveiro, em área estuarina. Foram avaliados quatro diferentes níveis de arraçoamento: 1, 3, 5 e 7% do peso vivo (PV) por dia. Avaliaram-se os seguintes parâmetros de desempenho: sobrevivência, biomassa final, taxa de crescimento específico, ganho de peso diário, conversão alimentar aparente, taxa de eficiência proteica, taxa de eficiência lipídica e índice hepatossomático. A sobrevivência foi superior a 80% em todos os níveis de arraçoamento. A conversão alimentar aparente mais eficiente foi obtida com a taxa de arraçoamento de 5% do PV por dia, que também resultou em melhores valores para o índice hepatossomático. A taxa de 5% do PV por dia proporciona melhor desempenho produtivo para o bijupirá em águas salobras.

USE OF TWO DIFFERENT MEGADOSES OF VITAMIN C IN THE FEED FOR FINGERLINGS NILE TILAPIA (OREOCHROMIS NILOTICUS) SUBMITTED TO EXPERIMENTAL INFECTION BY EDWARDSIELLA TARDA. Aiming to evaluate the effect of supplementation with megadoses of vitamin C on the diet of fingerlings from Nile Tilapia (Oreochromis niloticus), at the experimental infection by Edwardsiella tarda, two experiments were performed. Each experiment was composed by four distinct groups: those belonging to groups 1 and 4 received only commercial diet featuring about 300 mg of vitamin C per kilogram of feed, while the animals belonging to groups 2 and 3 received the same diet supplemented with 1,500 mg and 3,000 mg, respectively, of vitamin C (Lutavit® C Monophosphate – BASF) per kilogram of feed. In the first experiment the animals received the diet for 14 consecutive days, being infected on the 15th day, while in the second experiment the animals were infected by the bacterial suspension after an interval of more 14 days after the same period of supplementation with vitamin C. The results showed that although there isn’t a significant difference (p > 0,05) with respect to the concentrations of vitamin C, however the interval between the end of supplementati on with megadoses of vitamin C in the diet (Nutripeixe AL55 - PURINA) and bacterial exposure showed significant difference (p < 0,05) on the experimental infection with E. tarda in fingerlings of Nile Tilapia (O. niloticus).