This study was conducted to evaluate the influence of ingestion of different sources of starch on enzymatic and metabolic indicators in blood and liver of Rhamdia quelen. The experiment was conducted during 20 days in water recirculation system. Sixty fishes (initial average weight 60g) were used and divided into three treatments composed of the following diets: inclusion of peeled oats, defatted rice bran and control diet, all with 36% crude protein and 3,200 Kcal DE/Kg. There was no significant difference in growth parameters. The analysis demonstrated a reduction in liver glycogen content for the treatment with oats; however, no apparent changes in the activity of the enzymes alanine-aminotransferase and glucose-6-phosphatase were observed, raising the possibility that the fishes did not use gluconeogenesis. The blood analysis, showed no significant differences in the determinations of total cholesterol, HDL cholesterol and albumin; however, serum levels of total protein were higher for treatment with defatted rice bran, and triglyceride levels were lower in animals that received diet containing oat as starch source. It can be concluded that Rhamdia quelen is able to metabolize various sources of carbohydrate, without the need to use either diet or body protein as an energy source.