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.

Ana Basto,Susana C Fonseca,Tiago Sá,Lisa Petit,Josep Calduch-Giner,Luisa M P Valente,Margarida R G Maia,Jaume Pérez-Sánchez,Beatriz Oliveira,Elisabete Matos

doi:10.3389/fphys.2021.659567

Ana Basto, Susana C Fonseca + Show 8 more

Open Access

https://doi.org/10.3389/fphys.2021.659567

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Abstract

ObjectiveThis 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 MethodsFish (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.ResultsProtein 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.ConclusionIt 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.

Highlights

The use of insect protein as sustainable alternative to animal and plant protein sources has been encouraged for direct human consumption and incorporation into animal feeds (NogalesMérida et al, 2018; Salter, 2019)
The potential of T. molitor larvae meal (TM) to partially replace fishmeal (FM) in aquafeeds has been previously assessed in various marine fish species, such as European sea bass or sparids (Gasco et al, 2016; Piccolo et al, 2017; Henry et al, 2018; Antonopoulou et al, 2019; Iaconisi et al, 2019; Ido et al, 2019), whilst total replacement was only evaluated in red sea bream (Pargus major) (Ido et al, 2019)
The present study aimed to explore the impact of partial and total replacement of FM by dTM in a comprehensive approach focusing on growth performance and nutrient utilization, and on the underlying mechanisms involved in nutrient metabolism, namely lipid metabolism, in European sea bass

Summary

Introduction

The use of insect protein as sustainable alternative to animal and plant protein sources has been encouraged for direct human consumption and incorporation into animal feeds (NogalesMérida et al, 2018; Salter, 2019). Recent studies showed that insect-based diets modulate fish microbiota and improve the immune system, which may reduce the use of antibiotics in aquaculture (Bruni et al, 2018: Henry et al, 2018; Antonopoulou et al, 2019; Rimoldi et al, 2019; Stenberg et al, 2019; Li et al, 2021). In 2017, European Union (EU) authorized the use of insect meal (IM) from seven species, including yellow mealworm (Tenebrio molitor), in aquafeeds (European Commission, 2017). Basto et al (2020) have recently demonstrated that defatted (d-) T. molitor larvae meal (TM) is a highly digestible protein source able to meet European sea bass (Dicentrarchus labrax) EAA requirements (Basto et al, 2020). Results among authors are controversial, and the maximal replacement level of FM by TM are extremely variable and never exceeding 71% in diets for European sea bass (Gasco et al, 2016)

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