Effects of dietary levels of protein on nitrogenous metabolism of Rhamdia quelen (Teleostei: Pimelodidae).

This manuscript reports changes in key enzymes and metabolites related to protein metabolism and nitrogen excretion in the liver of juveniles jundiá (Rhamdia quelen) fed on isocaloric diets containing 20%, 27%, 34% and 41% of crude protein. The hepatic activity of alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GDH), and arginase (ARG) increased with the content of protein in the diet, and the ratios among the aminotransferases and GDH allowed evaluating metabolic preference. The concentration of free amino acids, ammonia and urea also rose with the dietary protein content.