Introduction
The reduction of the environmental footprint of diets for farmed fish that are nutritious but at the same time economically and environmentally sustainable has become a high priority (Naylor et al. 2021, Glencross et al. 2020). Turbot (Scophthalmus maximus), a high-value species in Europe, has a high potential for sustainable production and is suitable for diets with novel ingredients. Although alternative feed ingredients such as insect meal or processed animal protein have no or little effect on growth and feed performance, nutritional status indicators were negatively affected at low inclusion levels (Hoerterer et al. 2022). Using 1H-nuclear magnetic resonance (NMR) spectroscopy, this study examined the diet dependent effects on the metabolic response in muscle tissue of juvenile turbot after the fish were fed with different diets formulations including plant and animal protein sources.
Material and Methods
In a 16-week feeding trials with 750 juvenile turbot (20 ± 0 g), two formulation concepts were tested against a commercial formulation (CTRL). The alternative formulation concepts were based on replacing 20 % of fishmeal with insect meal and fermentation biomass. Furthermore, sustainable terrestrial plant proteins (NoPAP) or processed animal proteins (PAP) replaced the soybean content in the CTRL (see figure 1). The metabolic profile of a perchloric acid extract of the muscle and liver tissue of N = 45 juvenile (n = 15 per diet) was generated using 1H NMR spectroscopy (Rebelein et al., 2018). A Partial Least Squares - Discriminant Analysis (PLS-DA) of the metabolic profiles was performed to identify differences between the formulation concepts using MetaboAnalyst 5.0
Results and Discussion
The comparative approach revealed that metabolites associated with growth and energy allocation showed different levels in the muscle of fish fed with the alternative formulation concepts (NoPAP and PAP) and the commercial formulation (CTRL). Creatine levels were highest in fish from the CTRL group indicating fast energy provision in the body and good muscle growth. Furthermore, taurine levels were highest in muscle tissue of fish from the PAP group indicating that the dietary taurine (supplemented with 0.5 % in NoPAP and PAP) was metabolised better than in fish from the NoPAP group (see figure 2).
In general, the results from the 1H NMR generated metabolic profiles and following PLS-DA indicated that metabolites such as taurine, creatine, acetate and glutamine are diet-dependent in muscle tissue of turbot and that the NoPAP and PAP formulation concepts might affect the taste and consistence of muscle tissue of the final consumable product. More insight on the diet dependent effects on the energy allocation in turbot will bring the analysis of the liver of the juvenile turbots. Sensory analysis of the filets might confirm the NMR-based metabolite findings in the muscle.
References
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Hoerterer C, Petereit J, Lannig G, Johansen J, Pereira GV, Conceição LEC, Pastres R, Buck BH. 2022. Sustainable fish feeds: potential of emerging protein sources in diets for juvenile turbot (Scophthalmus maximus) in RAS. Aquaculture International.10.1007/s10499-022-00859-x.
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