Apparent digestibility coefficients of feedstuff used in tambaqui diets

Abstract

Quality of fish diet can be evaluated by quantifying the ability of fish to digest food. Therefore, this study aimed to determine the apparent digestibility coefficients (ADC) for crude protein (CP), ether extract (EE) and gross energy (GE) in nine protein ingredients and seven energy ingredients most commonly used in commercial diets for tambaqui. In total, 510 tambaqui juveniles were fed test diets containing a reference diet supplemented with an inert digestibility marker (Cr₂O₃) and each ingredient tested. Digestibility analyses showed that corn gluten had the highest ADC_CP (98.09%) and ADC_GE (96.91%), whereas alcohol yeast had the lowest ADCCP (63.17%) and ADC_GE (46.24%). Protein ingredients were revealed to be excellent sources of lipids (ADC_EE > 85.0%), with the exception of wheat gluten (ADC_EE: 63.73%). Corn (94.50%) and wheat bran (86.08%) showed the highest ADC_CP of all energy ingredients. No significant differences in ADC_EE were observed across the energy ingredients tested. Of the energy ingredients tested, corn oil (95.70%), fish oil (93.61%), soybean oil (93.31%) and corn (88.70%) had the highest ADC_GE. The use of protein ingredients and energy ingredients with high digestibility coefficients, such as the ones reported, can guide the formulation of top quality diets for tambaqui.