Performance, carcass composition and nutrient utilization of surubim Pseudoplatystoma coruscans (Agassiz) fed diets with varying carbohydrate and lipid levels

Five isonitrogenous diets formulated to contain 470 g kg^?1 of crude protein, five different levels of crude lipids (190, 210, 230, 250 and 270 g kg^?1), five different levels of carbohydrates (178, 155, 158, 125 and 110 g kg^?1) and gross energy (21.2, 21.6, 22.4, 22.8 and 23.2 MJ kg^?1) were used to investigate the effect of dietary lipid levels on performance and carcass composition of the surubim, Pseudoplatystoma coruscans (Agassiz). Triplicate groups of 11 fish with an average individual body weight of 5.1 ± 0.2 g were randomly assigned to 15 net cages and fed each test diet twice a day to apparent satiation for 64 days. At the end of the trial there were no significant differences in feed consumption or fish performance. No differences (P > 0.05) were observed in the lipid content of fish carcass and liver. On the contrary, visceral lipid increased (P < 0.05) with the increase in dietary lipid level. Protein and energy retention efficiencies were not significantly affected (P > 0.05) by the dietary lipid and carbohydrate levels. The results of this trial suggest that increasing dietary lipid levels from 190 to 270 g kg^?1 did not improve growth performance or protein sparing and caused an undesirable increase in the visceral lipid content of surubim fingerlings.