Effects of dietary protein level on growth and serum parameters in cachama (Piaractus brachypomus)

Blood chemistry parameters are valid and useful indicators to determine the nutritional status and health of farmed fish. These parameters allow establishing normal health, detecting physiological disorders and providing information for diagnosis and prognosis of diseases caused by nutritional and environmental factors. Objective: to analyze the growth and changes in biochemical parameters in plasma of juvenile tambaqui (Piaractus brachypomus) fed two protein levels. Methods: fish were fed diets with 24 and 34% of digestible protein. Experiments were conducted in laboratory tanks, dam cages, and earthen ponds to evaluate weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), as well as serum variables such as glucose, total protein, cholesterol, triglycerides, and urea. Fish were sampled at the beginning and end of the experiments for determining body weight and to draw blood samples. In experiments 2 and 3 fish were monthly sampled for four months (three animals per replicate). Results: no differences were found between treatments (p>0.05) for GP and SGR. The PER values in laboratory tanks and cages showed inverse linear correlation with respect to protein level (p0.05), except cholesterol and urea in the laboratory. The observed initial values differed from those obtained during the course of the experiments (p0.05), porem, os dados de PER em gaiolas e laboratório mostraram uma correlação lineal inversa com relação ao nível de proteína (p0.05) para GP y SGR. Los valores de PER en jaulas y laboratorio mostraron correlación lineal inversa con relación al nivel de proteína (p0.05), excepto colesterol y úrea en laboratorio. Los valores observados al inicio difirieron de los observados durante el desarrollo de los experimentos (p