Desempenho produtivo, perfil de aminoácidos plasmáticos em tilápias do Nilo alimentadas com dietas com diferentes concentrações de aminoácidos cristalinos

Abstract

Crystalline amino acids have been emerging in plant-based diets for tilapias to improve the nutritive value and consequently optimize feed efficiency and growth of fish. The present study aimed to evaluate the productive performance and plasma amino acid profile of Nile tilapia juveniles fed different concentrations of crystalline amino acids. Three diets with 423 g kg-1 of crude protein and 3600 kcal kg-1 of digestible energy were designed to meet the requirements of juvenile Nile tilapia, based on fishmeal protein without crystalline amino acid (ALP) supplementation, 12% crude protein (CP) of crystalline amino acids (AC12) and 24% of CP of crystalline amino acids (AC24). Sodium bicarbonate was added to the AC12 and AC24 diets to adjust the pH to 7.0. 360 (initial weight 4.3 ± 0.1g) juveniles of Nile tilapia were distributed in a recirculation system, with 24 aquariums of 70 L, with 15 fish each. The fish were fed manually, six times a day, for eight weeks. In a completely randomized design, with three treatments and eight repetitions. For the plasma amino acid profile, data were analyzed using a 3 x 6 factorial design, with three diets (ALP, AC12 and AC24) and six times (0; 60; 120; 240; 480 and 960 min post-feeding) collection. Fish fed the ALP and AC12 diet had higher final weight, weight gain, growth rate, protein efficiency rate and feed conversion, compared to fish that consumed the AC24 diet. There was an interaction between diet and time for the plasma level of methionine and threonine. Fish fed the AC24 diet showed plasma methionine peak at 240 min post-feed, while the methionine peak in fish fed the ALP and AC12 diets occurred later at 480 min. Fish that received the AC24 diet showed a threonine peak 120 min after feeding, while the plasma threonine peak occurred at 240 min in fish fed the ALP and AC12 diets. The level of lysine was higher in fish fed the AC24 diet, compared to the plasma level in fish fed the ALP and AC12 diets. Using post-feeding time as a response criterion, the quadratic regression analysis estimated the peaks of plasma arginine and lysine at 532 and 527.5 min, respectively. It was concluded that supplementation of crystalline amino acids in up to 12% of CP is equivalent to productive performance, and retention of amino acids to the performance of Nile tilapia juveniles fed the diet without the addition of crystalline amino acids. The diet with 24% protein derived from crystalline amino acids results in asynchrony in the use of amino acids, impairing the retention of amino acids and, consequently, the productive performance of the fish.