Two experiments were carried out aiming to compare techniques of digestibility of fish food nutrients, by using external indicators (chromic oxide and barium carbonate), internal indicators (HCl-insoluble ash, acid detergent insoluble ash, crude fiber and acid detergent fiber) and the direct determination technique. Corn meal was used in the first experiment and soybean meal was used in the second one; both used 100 g tambaquis. Chromic oxide and barium carbonate are effective external indicators for estimating the digestibility coefficients of feedstuffs fed to tambaquis. Crude fiber and the acid detergent fiber present a low recovery and do not estimate accurately the digestibility coefficients of feedstuffs for tambaquis and also underestimate them. The insoluble ash in acid and the insoluble ash in detergent acid showed high recovery percentage and accurately estimated the digestibility coefficients of feedstuffs fed to tambaquis, when showed contents higher than 3.8 and 3.1, respectively. The direct determination technique was efficient to estimate the digestibility coefficients of the food given to the tambaquis.
aquaculture; digestibility; nutrition; tambaqui
