Aimed to evaluate the growth performance and body composition of juvenile tambacu fed diets containing increasing levels of cellulose. 128 juveniles (29.0±6.0g) were distributed into 16 tanks (150 L), at a density of eight fish per tank, in a completely randomized design with four treatments (increasing levels of cellulose: 0, 20, 40 and 60 g kg-1) and four replications. For the growth performance parameters it was evaluated: final weight (FW), feed intake (FI), weight gain (WG), feed conversion rate (FCR), protein efficiency rate (PER) and survival (SUR). For the analysis of body composition, dry matter (DM), crude protein (CP), ether extract (EE), gross energy (GE) and mineral matter (MM) were analyzed. There was a quadratic response (P<0.05) to the FW, FI, WG and FCR variables with the best results obtained, respectively, to levels of 19.95, 11.22, 19.87 and 23.86 g kg-1 of inclusion of cellulose in the rations. There was no effect (P>0.05) of levels of inclusion of cellulose on the PER, SUR and on the parameters of body composition in DM, CP, EE, GE and MM. Diets with high inclusion levels of cellulose adversely affected the performance of juvenile tambacu. However, the physiological and metabolic changes caused by these rations were not sufficient to affect body composition.
body composition; Colossoma macropomum; dietary fiber; growth performance; Piaractus mesopotamicus