The Use of Defatted Tenebrio molitor Larvae Meal as a Main Protein Source Is Supported in European Sea Bass (Dicentrarchus labrax) by Data on Growth Performance, Lipid Metabolism, and Flesh Quality

© 2021 Basto, Calduch-Giner, Oliveira, Petit, Sá, Maia, Fonseca, Matos, Pérez-Sánchez and Valente.[Objective]: This study aims to determine the maximal inclusion level of defatted (d-) Tenebrio molitor larvae meal (TM) able to replace dietary fishmeal (FM) without compromising growth performance, general metabolism, and flesh quality traits in European sea bass, and to evaluate the major underlying physiological mechanisms. [Materials and Methods]: Fish (55 ± 2 g) were fed with diets containing increasing levels of dTM: 0, 40, 80 and 100% (CTRL, TM40, TM80, and TM100, respectively) to replace FM. After 10 weeks of feeding, the growth performance, nutrient and energy balance, intestinal integrity, plasma metabolites and the expression of genes related to growth and nutrient metabolism, in liver and muscle were determined. The fatty acids (FA) profile, textural properties and color were also evaluated in muscle. [Results]: Protein and lipids digestibility remained unaltered up to 80% dTM inclusion. Growth performance parameters were similar among dietary treatments. The dTM inclusion increased the hepatosomatic index in fish fed TM100. Muscle eicosapentaenoic acid, docosahexaenoic acid and n-3 long-chain polyunsaturated FA levels were maintained up to 80% dTM inclusion, but total cholesterol and non-esterified FA increased with dietary dTM inclusion. In liver, the expression of elongation of very long-chain FA protein 6 (elovl6) and FA desaturase 2 (fads2) did not change in fish fed TM40 and TM80, but elovl6 decreased whilst fads2 increased in fish fed TM100 when compared to those fed CTRL. The expression of cholesterol 7 alpha-monooxygenase (cyp7a1) decreased with dietary dTM inclusion. In muscle, the expression of myoblast determination protein-2 (myod2) decreased in fish fed TM80 and TM100. [Conclusion]: It is feasible to substitute dietary FM by dTM up to 80% in European sea bass without detrimental effects on nutrient digestibility, growth performance and associated genetic pathways, whilst assuring fillet nutritional value for human consumption.This work was funded by the EU H2020 Research Innovation Program under the TNA Program (project AE090027) at IATS-CSIC Research Infrastructure within AQUAEXCEL2020 Project (652831). Additional financial support was received by the structured program of R&D&I ATLANTIDA - Platform for the monitoring of the North Atlantic Ocean and tools for the sustainable exploitation of the marine resources (reference NORTE-01-0145-FEDER-000040), supported by the North Portugal Regional Operational Programme (NORTE2020), through the European Regional Development Fund (ERDF) and by ANIMAL4AQUA Project, funded by Portugal 2020, financed by ERFD through COMPETE – POCI-01-0247-FEDER – 017610. This output reflects only the author’s view and the European Union cannot be held responsible for any use that may be made of the information contained herein. AB and MM were financially supported by FCT, Portugal (SFRH/BD/138593/2018 and DL57 – Norma transitória, respectively). Financial support from FCT – Foundation for Science and Technology within the scope of UIDB/04423/2020 and UIDP/04423/2020 is also acknowledged