Crescimento, hematologia e metabolismo de pacu (Piaractus mesopotamicus) submetido ao exercício aeróbico e alimentado com níveis crescentes de proteínas

Abstract

The composition of the diet, the metabolic adaptations and variations in the activity of the fish are the main factors responsible for seasonal changes in physiological variables. It is known that aerobic exercise can improve the fish growth due to: the enhancement of feed conversion, reduced dominance, increased protein synthesis and lipid and glucose catabolism. The diet must satisfy the nutritional requirements of each species. Knowledge of the appropriate protein level is critical because maximizes feed conversion efficiency, lowers costs and reduces the load of nutrients released to the aquatic ecosystem. In Brazil, the pacu, Piaractus mesopotamicus, is an important fish in aquaculture, especially for hardiness, fast growth, excellent meat quality. This species may respond to exercise with lower levels of protein catabolism and for directing them to growth. Thus, a balanced diet and a well established aerobic exercise protocol could promote better growth for pacu. This study aimed to evaluate the effects of the combination of different levels of crude protein in the diet and sustained exercise in pacu through growth performance, hepatosomatic and viscerosomatic indexes, metabolic and hematological parameters. The experiment followed a completely randomized 2 x 3 factorial arrangement, consisting of two swimming activities (exercised-E, non-exercising) and three levels of dietary protein percentage (24, 28 and 32). The pacu exercised and fed 24 % crude protein (CP) showed better growth. The hematologic variables were responsive to nutritional status and exercise. When comparing the exercised groups all together, it was observed that the high levels of CP in the diet increased protein catabolism and lipogenesis in the liver and white muscle and lipid catabolism in red muscle. High levels of CP in the diet of non-exercised pacu increased protein catabolism in white muscle and lipogenesis in the liver. Sustained swimming activity increased the use of liver glycogen at all levels of protein studied, and protein anabolism and lipogenesis in pacu fed higher-protein diet. Based on the responses obtained in this study we can infer that for exercised pacu, the appropriate level of protein in the diet is 24 % of crude protein and levels above that promote the use of protein as an energy source.