Exercício aeróbico e suas implicações no crescimento e metabolismo de pacu (Piaractus mesopotamicus)
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Fishes as well as other group of species can accrue benefits from adapting to aerobic exercises. Examples of these benefits are: higher growth and feed conversion rates, less aggressive behavior, and optimization of non-nitrogenous nutrient as source of metabolic energy. The aim of this work was to evaluate growth and metabolic responses of pacu (Piaractus mesopotamicus) to aerobic swimming speeds and diets, varying in proportions of carbohydrates and lipids. Two experiments were carried out. One of it aimed to determining the ideal aerobic swimming speed for pacu; three speeds were compared: 1 body-length per second (BL/sec), 2 BL/sec, and 3 BL/sec besides a control treatment (non-exercised). In the second experiment the fish were kept at non-exercising or swimming at the ideal speed determined in the previous experiment, and submitted to different feeding regimes, in which the diets presented varying proportions (%) of carbohydrate and lipid, respectively: 27/15, 36/10 and 45/5. In both experiments, treatment effects were evaluated in terms of zootechnical parameters, several hematological variables, and intermediary plasmatic, hepatic and muscle tissue (white and red) intermediary metabolites and several metabolic enzyme activities. It was concluded from the first experiment that swimming at 2 BL/sec was ideal for pacu, considering the comparatively higher rate of growth and a metabolic response indicative of a higher utilization of non-protein sources for energy production. The spare-protein effect was also observed under the 1 and 2 BL/sec treatments while higher levels of protein oxidation, possibly for the maintenance of energy levels, and adequate levels of glycemia were observed in the individuals kept swimming at 3 BL/seg. In the second experiment, the best growth rates were presented by swimming fishes kept under the 36/10 feeding regime; a higher participation of lipids as metabolic energy supplier was also noted under this regime. It was concluded that pacu submitted to aerobic swimming at 2 BL/sec and fed with diet containing 36% lipids and 10% carbohydrates presented better growth performance and higher efficiency in directing non-protein sources for metabolic energy production.