Apparent digestibility of nutrients and energy from selected protein sources for tambaqui (Colossoma macropomum)

Abstract

This research aimed to evaluate the chemical composition and apparent digestibility coefficients (ADC) of dry matter (DM), gross energy (GE), crude protein (CP), and amino acids (AA) in plant and animal protein sources used in aquafeeds for tambaqui (Colossoma macropomum). Tested ingredients were soybean meal (SBM), cottonseed meal (CSM), corn gluten meal (CGM), fish meal (FM), meat and bone meal (MBM), and poultry by-product meal (PBM). A reference diet was formulated to contain 287 g kg−1 CP and 18.5 MJ GE kg diet−1, and test diets were produced by incorporating test ingredients in a 70:30 ratio. Chromic oxide (Cr2O3) was used as an inert marker at 2 g kg−1, and feces were collected by sedimentation. High variation in the ADC of DM (0.577 to 0.958) and GE (0.506 to 0.953) was observed between protein sources, while the ADC of CP was higher and showed less variation between the ingredients (between 0.834 and 0.978). The CGM, FM, and PBM treatments had the highest ADC values and appeared adequate for compounding aquafeeds for tambaqui, while CSM and MBM showed the lowest ADC values. Interestingly, the ADC of AA was variable among ingredients (from 0.272 to 0.989) and did not show the same trend as the other nutrients (mainly the CP). The present study demonstrates that tambaqui can efficiently digest both plant and animal protein sources. However, overall digestibility of plant protein sources appeared lower when extrusion was used to manufacture the diets.