Digestibility of extruded peas, extruded lupin, and rapeseed meal in rainbow trout (Oncorhynchus mykiss) and turbot (Psetta maxima)

Apparent digestibility coefficients (ADC) of nutrients and energy of extrud ed peas, extruded lupin and rapeseed meals were determined in juvenile rain bow trout and turbot. Extruded lupin was found to be a promising substitute for fish meal in the diets of trout and turbot, with an acceptable digesti bility of its dry matter (70% in trout and 81% in turbot) and a high digest ibility of its protein (96% in trout and 98% in turbot) and its energy (77% in trout and 85% in turbot). Extruded peas had a lower digestibility of it s protein in trout (88%) than in turbot (92%), and the ADC of energy, mainl y supplied as starch, was relatively low (69% in trout and 78% in turbot). The digestibility of rapeseed meal was improved by a thermal treatment. Wit hout thermal treatment, rapeseed meal had a low digestibility of its dry ma tter (57%) and energy (69%) in turbot. The availability of phosphorus was h igher for extruded lupin (62% in trout and 100% in turbot) compared to the other plant-ingredients. When compared to a solvent-extracted meal, the ava ilability of phosphorus from rapeseed meal was improved by heat treatment i n both species (42% vs. 26% in trout and 65% vs. 49% in turbot). (C) 2000 E lsevier Science B.V. All rights reserved.