Exigências dietéticas de lisina e metionina para fêmeas de lambaris-do-rabo-amarelo (Astyanax altiparanae) na terminação

Abstract

Two studies were carried out to determine the dietary lysine and methionine requirement for finishing "lambari-do-rabo-amarelo" (Astyanax altiparanae) females through growth performance, whole body composition, activity of the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and muscle growth. In both experiments, fish were fed with extruded diets, until apparent satiety, six times per day. In the first experiment, during 95 days, 480 fish (4.96±0.02 g) were distributed into 24 aquaria (70-L each). Six extruded isonitrogenous (345.0 g kg-1 of crude protein) and isoenergetic rations (19.51 MJ kg-1 of gross energy) were elaborated to contain 12.13, 13.31, 15.36, 18.79, 19.92 and 23.02 g kg-1 of lysine. Based on the linear response plateau (LRP) analysis and in the weight gain and specific growth rate parameters, the dietary lysine requirement of finishing "lambari-do-rabo-amarelo" was estimated at 18.72 g kg-1 and 18.46 g kg-1 lysine, respectively. Based on whole body composition, the dietary lysine requirement was estimated at 18.75 g kg-1 lysine (5.42% of dietary protein), through second-order regression analysis, for the lower content of lipids. The activity of ALT and AST enzymes in the blood serum of fish was lower in fish fed with the lowest levels of the dietary lysine. Fish fed graded levels of ditary lysine did not show significant differences in the muscle growth. It was concluded that the dietary lysine requirement of finishing female "lambari-do-rabo-amarelo" is 18.72 g kg-1 (5.41% of the diet protein). In the second study, also with a period of 95 days, 264 finishing females of "lambari-do-rabo-amarelo" (6.10±0,11 g) were distributed into 24 aquaria (70-L each). Six extruded isonitrogenous (310.0 g kg-1 of crude protein) and isoenergetic (19.76 MJ kg-1 of gross energy) diets were elaborate to contain 6.71; 8.31; 11.31; 13.12; 15.59 and 19.74 g kg-1 of methionine + cystine. It was observed a quadratic effect of methionine+ cysteine levels on the weight gain, specific growth rate and protein efficiency ratio, and the dietary methionine + cystine requirements of female finishing "lambari-do-rabo-amarelo" was estimated at 13.66 g kg-1, 13.52 g kg-1 and 13.17 g kg-1, values corresponding to 4.40%, 4.36 and 4.25% of crude protein, respectively. No significant differences on whole body composition, activity of enzymes ALT and AST and muscle growth of fish fed with graded levels of dietary methionine + cystine were observed. It was concluded that the dietary methionine + cystine requirement for finishing female of "lambari-do-rabo-amarelo" is 13.52 g kg-1 (4.36 % of the diet protein).