Effect of Dietary Energy Sources on the Utilization of Protein by Colossoma macropomum Fingerlings

Abstract

The effects of dietary energy sources on protein utilization by Colossoma macropomum fingerlings were studied. The fish were fed to satiation seven experimental isocaloric semi-purified casein diets with increasing dietary protein levels (from 0 to 48%). The energy content was adjusted with carbohydrates in four diets (11, 20, 31 and 48% protein) and with lipids in two diets (28 and 36% protein). Daily feed consumption decreased and percent gain and feed efficiency increased with an increase in dietary protein. Dietary protein requirement was found to be more than 31% when carbohydrates were used as the energy source. Protein efficiency ratio and net protein utilization were inversely proportional to the dietary protein content and no negative effect of carbohydrates on protein utilization was observed. In terms of feed efficiency and protein efficiency ratio, the lipid and carbohydrate groups responded in a similar way to the dietary protein levels. Carbohydrates seemed to be effective as a dietary energy source for this species. The whole body lipid content was inversely proportional to the dietary protein level and was higher in fish fed the lipid diets than in those fed the carbohydrate diets. © 1995, The Japanese Society of Fisheries Science. All rights reserved.