ABSTRACT
A 90-day feeding trial was conducted to estimate the dietary lysine requirement of adult lambari ( Astyanax altiparanae ), based on growth performance, whole-body composition, muscle development, and aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. Six isoproteic (345.0 g kg−1) and isoenergetic (19.51 MJ kg−1) diets were formulated, and crystalline L-lysine was added to obtain diets with lysine concentrations of 12.13, 13.31, 15.36, 18.79, 19.92, and 23.02 g kg−1 dry diet. Female adult lambari (n = 480; weight of 4.96±0.02 g) were distributed into 24 (70 L) aquaria and fed the experimental diets six times daily. Fish fed 12.13 to 19.92 g kg−1 lysine showed increased weight gain and percent weight gain, and fish from those treatments also showed improvement in final carcass quality by a decrease in whole-body lipid content. Fish fed 12.13 g kg−1 lysine showed lower ALT and AST activities in blood serum when compared with fish fed the highest lysine levels. No differences were observed in muscle growth in fish fed graded lysine levels. According to the broken-line model analysis of weight gain and dietary lysine levels, the dietary lysine requirement of adult lambari is estimated at 18.72 g kg−1 (5.41% of dietary protein).
Key Words:
aminoacid; carcass quality; fish nutrition; lysine; nutritional requirement
