Feeding high inclusion of whole grain white lupin (Lupinus albus) to rainbow trout (Oncorhynchus mykiss): effects on growth, nutrient digestibility, liver and intestine histology and muscle fatty acid composition Aliro Borquez 1 , Edison Serrano 1,2 , Patricio Dantagnan 1 , Jaime Carrasco 3 & Adrian Hernandez 1 1 Escuela de Acuicultura, Universidad Cato¤ lica deTemuco,Temuco, Chile 2 Department of Animal and Aquacultural Sciences, Aquaculture Protein Centre, Centre of Excellence, Norwegian University of Life Sciences, Aas, Norway 3 BioMar Chile S.A., Puerto Montt, Chile Correspondence: E Serrano, Escuela de Acuicultura, Universidad Cato¤ lica deTemuco, Casilla15-D,Temuco, Chile. E-mail: eserrano@uct.cl Abstract The e¡ect of dietary inclusion of whole grain white lupin ( Lupinus albus ) on growth performance, histol- ogy, muscle fatty acid composition and nutrient di- gestibility was investigated in an 11-week growth and a 4-week digestibility trial with rainbow trout (initial body weight of 54.0 Æ 6.2 and 181.9 Æ 3.4 g respectively). Four experimental extruded diets were formulated to contain 0%, 30%, 40% and 50% of whole grain lupin and fed to triplicate groups of ¢sh twice a day until apparent satiation. Faeces were col- lected daily from each digestibility tank by decanta- tion. No signi¢cant trends were observed with respect to growth, feed utilization, apparent digest- ibility coe/cients or whole-body composition ( P40.05). Conversely, increasing levels of dietary lu- pin led to signi¢cant decreases in the Hepatosomatic index ( R 2 50.75, Po0.05) and slight lipid in¢ltration into hepatocytes and enterocytes. Muscle fatty acid compositions were slightly a¡ected by the dietary treatment. Polynomial regression of dietary inclusion of lupin and muscle fatty acid concentrations showed an increase in C18:1n-9, C18:2n-6 and C18:3n-3 and a decrease in C20:5n-3 with increasing dietary lupin level.These results demonstrated that whole grain lu- pin can be included up to 50% in commercial rain- bow trout diets without negative e¡ects. Keywords: lupin, growth performance, digestibil- ity, fatty acid, histology Introduction Historically, salmonid diets have been formulated to contain ¢sh meal as the most important source of dietary protein, comprising between 20% and 50% of the total ingredients (Watanabe 2002;Tacon & Me- tian 2008). The current production of ¢sh meal is not su/cient to cover increasing demand from the aqua- culture sector (Tveteras & Tveteras 2010). This has led to the partial replacement of ¢sh meal with alter- native sources of protein, primarily of plant origin such as legumes and oilseeds (Hardy1996; Glencross, Booth & Allan 2007). Lupin seeds have been used successfully as a replacement for ¢sh meal in aquaculture feeds of salmonids and other marine ¢sh (De la Higuera, Gar- cia-Gallego, Sanz, Cardenete, Suarez & Moyano 1988; Robaina, Izquierdo, Moyano, Socorro, Vergara, Mon- tero & Fernandezpalacios 1995; Burel, Boujard, Cor- raze, Kaushik, Boeuf, Mol, Van der Geyten & Kuhn 1998; Burel, Boujard, Kaushik, Boeuf,Van der Geyten, Mol, Kuhn, Quinsac, Krouti & Ribaillier 2000; Carter & Hauler 2000; Farhangi & Carter 2001; Aslaksen, Aquaculture Research, 2010, 1^12 doi: 10.1111/j.1365-2109.2010.02690.x r 2010 The Authors Journal Compilation r 2010 Blackwell Publishing Ltd 1 Are 2690