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Article

Redesigning Aquafeeds: Insect, Algae, and By-Product Blends Sustain Growth and Nutritional Value in European Sea Bass Under Feeding Constraints

by
Daniel Montero
1,*,
Marta Carvalho
1,
Silvia Torrecillas
1,2,
Luís E. C. Conceição
3,
Filipe Soares
3,
Félix Acosta
1 and
Rafael Ginés
1
1
Grupo de Investigación en Acuicultura (GIA), Instituto Universitario ECOAQUA, Universidad de Las Palmas de Gran Canaria, 35001 Las Palmas, Canary Islands, Spain
2
Aquaculture Program, Institut de Recerca i Tecnología Agroalimentaries (IRTA), 43540 La Rápita, Tarragona, Spain
3
SPAROS Lda., Área Empresarial de Marim, 8700-221 Olhão, Portugal
*
Author to whom correspondence should be addressed.
Fishes 2026, 11(2), 75; https://doi.org/10.3390/fishes11020075
Submission received: 26 November 2025 / Revised: 9 January 2026 / Accepted: 19 January 2026 / Published: 23 January 2026
(This article belongs to the Section Nutrition and Feeding)
Versions Notes

Abstract

Background: Adopting novel feed ingredients and aligning feeding strategies with these formulations are key to improving aquaculture sustainability. This study assessed the combined effects of alternative protein and lipid sources and feeding regime on growth, nutrient utilization, and body composition of European sea bass (Dicentrarchus labrax) juveniles. Methods: Two isoenergetic and identical digestible protein diets (39%) were formulated: a control (conventional fishmeal/fish oil (FM/FO) and plant proteins, containing 20% FM and 6% FO) and an alternative diet replacing 50% of FM and 25% of vegetable proteins with a blend of poultry by-products, insect meal, and single-cell protein (Corynebacterium glutamicum) and totally replacing fish oil with alternative lipid sources (microalgae and by-product oils). Fish (28 g of initial body weight) were fed for 210 days either to apparent satiety (AS) or under moderate restriction (85% and 65% of AS). The number of fish used was 65 fish per 500 L tank (triplicate for each experimental group). Growth performance, feed conversion, nutrient efficiency ratios, protein retention, and proximate and fatty acid composition were measured. Results: The alternative diet significantly improved growth, feed and nutrient efficiency, and protein retention compared with the control. Whole-body fatty acid profiles of fish fed the alternative diet showed higher contents of nutritionally important fatty acids, including DHA. Restricted feeding at 65% of AS enhanced nutrient efficiency ratios and protein retention relative to 85% and AS, but reduced growth. Feeding to AS produced the highest feed intake and growth but poorer feed conversion and nutrient efficiency. No significant interaction between diet and feeding strategy was observed. Conclusions: Incorporating novel protein and lipid sources can improve sea bass performance and product nutritional value while supporting sustainability. Feeding at ~85% of AS may offer a practical compromise between growth and efficient nutrient utilization.
Keywords:
feeding strategy; novel feed; nutrient efficiency; sea bass
Key Contribution: This study demonstrates that alternative diets incorporating novel protein (poultry by-products; insect meal and single-cell protein) and lipid sources (microalgae; poultry and salmon by-products) can enhance growth, feeding efficiency, and DHA content in European sea bass juveniles compared to conventional formulations. Moreover, feeding at 85% of apparent satiety optimized the trade-off between growth and nutrient utilization, supporting sustainable aquaculture practices without compromising fish performance or product quality.

1. Introduction

As global aquaculture continues to expand rapidly, the reliance on finite resources such as fish meal (FM) and fish oil (FO) derived from wild stocks within sustainability thresholds defined by responsible fishery management and ecosystem productivity limits remains a major challenge, even at the substantially reduced inclusion levels currently employed commercially across species, particularly in marine fish. The finite availability of FM and FO raises critical concerns regarding the long-term sustainability of aquaculture production [1]. In addition, fluctuations in the availability and market prices of these raw materials impose economic pressures on producers and, consequently, consumers [2]. In response, over the past decades, the aquafeed industry has progressively shifted towards more sustainable feed ingredients, with plant-derived raw materials initially occupying a predominant role [3]. Nevertheless, fish species differ in their capacity to digest and utilize plant-based ingredients efficiently, and in marine carnivorous species in particular, the use of plant-based diets can lead to potential nutritional deficiencies and compromised growth performance and/or health, as well as decreasing the nutritional value of aquaculture products for the consumers [3]. To counterbalance these limitations and to reinforce both the sustainability and the integrity of the aquaculture sector, several novel ingredients have been widely studied in recent years [4,5,6].
Insect meals (IM), such as those derived from black soldier fly (Hermetia illucens) or yellow mealworm (Tenebrio molitor) meals, have been positioned as a suitable alternative to FM due to their high protein content, balanced essential amino acid profile, efficient production, low resource dependency, and contribution to a circular economy [7,8,9]. Likewise, microalgae, particularly in oil forms (MO), offer promising benefits due to their high n-3 LC-PUFA content and simple nutritional requirements. Their low carbon footprint enhances their potential to reduce dependence on FM and, especially, FO in aquafeeds [10,11]. Despite these advantages, the widespread adoption of such novel ingredients remains constrained by high production costs and limited production volumes. Consequently, a diversified strategy incorporating a broad variety of raw materials is recommended to achieve cost-effective and sustainable feeds [12,13,14,15]. Therefore, the combination of novel ingredients with other already used conventional low-cost alternatives, such as animal by-products like poultry meal (PM), poultry oil (PO), and salmon oil (SO), can enhance flexibility in aquafeed formulations. This strategy also permits preserving the nutritional quality and sustainability requirements of the feeds, and thus contributing to the productive, environmental and economic goals of the industry [3,16,17].
Moreover, to fully assess the potential of alternative and novel ingredients, it is also crucial to implement appropriate feeding strategies [18], which can vary between species and may range from feeding ad libitum until apparent satiation to a restricted ration based on a proportion of body weight or on feed input to a culture system [19,20]. Restricted feeding strategies, which involve carefully controlling the amount of feed provided to fish, can be of great interest for environmental and economic reasons, as they reduce the environmental impact associated with feed waste as well as the production costs associated with feeding [21,22]. In theory, for most species, optimized feed utilization, and thus optimal feed and nutrient efficiency, occurs at a feeding rate above the maintenance feeding level but below the satiation level [22,23,24,25]. However, when using feeds with alternative ingredients of different composition and digestibility, different feeding strategies are hypothesized to significantly affect nutrient intake and utilization, and consequently fish metabolic processes, growth performance and body composition of the farmed species. Furthermore, tailoring the feeding strategy to specific dietary conditions could potentially help mitigate nutritional imbalances and negative metabolic consequences often associated with alternative feed formulations [18]. Despite this, existing data on the long-term effects of different feeding strategies and moderate levels of dietary restriction of ration size on fish growing on different dietary treatments are scarce [18], and, to our knowledge, no studies have been conducted in this regard on European sea bass (Dicentrarchus labrax).
In this context, adopting a holistic approach that integrates novel feed formulations with tailored feeding strategies is essential to improve productivity in aquaculture. Such integration also supports environmental and economic sustainability across production systems. Therefore, the present study investigated the combined long-term effects of innovative feed formulations—characterized by high FM and FO replacement using alternative ingredients—and different feeding regimes (two moderately restricted rations vs. apparent satiation) in European sea bass. The assessment encompassed growth performance, feed utilization, nutrient retention, proximate composition, fatty acid profiles, and whole-body fatty acid retention.

2. Materials and Methods

2.1. Experimental Diets

Two isoenergetic diets were formulated and used in the study: a control diet (C) containing 20% fish meal (FM) and 6% fish oil (FO) and an alternative diet (ALT) in which 50% of FM and 25% of vegetable proteins (particularly those derived from soy) were substituted with a blend of poultry by-product meal (PBM), insect meal (IM) and a single-cell protein from Corynebacterium glutamicum, while FO was entirely replaced by a mixture of microalgae oil (MO), poultry by-products oil (PO), and salmon by-product oil (SO). Feeds were manufactured by Sparos Lda. (Olhão, Portugal) and analyzed at UI-ECOAQUA laboratory (Telde, Las Palmas, Spain) following the methodology described in Section 2.4. Formulation of the diets, proximal composition and amino acid and fatty acid profiles of the diets are shown in Table 1 and Table 2.

2.2. Experimental Conditions and Fish

In total, 1170 European sea bass juveniles from a local farm (Aquanaria, Gran Canaria, Spain) were acclimated to the aquaculture facilities of Universidad de Las Palmas de Gran Canaria (ULPGC) (Telde, Canary Islands, Spain) for 3 weeks under the same environmental parameters as those used during the feeding trial and fed the same commercial diet for this species that was feeding on the farm. After the acclimation period, fish (initial body weight of 28.25 ± 0.71 g) were allocated to 18 tanks each with a capacity of 500 L and provided with a flow-through system with a renovation rate of one tank per hour. The initial stocking density was set at 65 fish per tank (triplicate tanks per each experimental group). Fish were manually fed three times daily, and the amount of feed supplied, as well as uneaten feed, was weighed daily to calculate the amount of ingested feed. Three different feeding strategies were employed: feeding until apparent satiety (AS) (based on visual apparent satiety), feeding at 85% of AS (85%), and feeding at 65% of AS (65%). Diet rations were adjusted daily considering the amount fed by the AS group. Each experimental group (diet x feeding dose) was tested in triplicate. Fish were fed the experimental diets for 210 days. Throughout the experiment, the experimental conditions were maintained under a natural photoperiod (12 h light/12 h dark); the average water temperature was 21 ± 0.31 °C, and the dissolved oxygen level was measured between 6.5 and 7.1 ppm. All parameters were measured continuously at the facilities using the Miranda® system (Innovaqua, Seville, Spain).
Fish were sampled at the beginning (three pools of 6 fish from the initial population) and at the end (6 fish per tank) of the trial for whole-body composition analysis. Before sampling, all fish were euthanized with an excess of anesthesia (clove oil: 5 mL/L).

2.3. Zootechnical Parameters

All fish were individually weighed and measured in monthly samplings after fasting for 24 h. Fish were anesthetized with natural clove oil (0.2 mL/L). Productive parameters were calculated following the respective equations:
SGR, Specific Growth Rate (SGR) = [(Ln (final weight − Ln (initial weight))/days of feeding];
Weight Gain (WG) = final weight − initial weight;
Feed Conversion Ratio (FCR) = feed intake/weight gain;
K index = weight/length3 × 100;
Furthermore, nutrient efficiency ratios and retentions were estimated based on the following formulae:
Protein Efficiency Ratio (PER) = weight gain/protein intake;
Lipid Efficiency Ratio (LER) = weight gain/lipid intake;
Protein retention (%) = ((Protein content in final body × final body weight) − (Protein content in initial body × initial body weight))/(Protein content in diet × feed intake) × 100;
Lipid retention (%) = ((Lipid content in final body × final body weight) − (Lipid content in initial body × initial body weight))/(Lipid content in diet × feed intake) × 100;
Fatty acid retention (% fatty acid intake) = ((final weight × FA in final whole-body × final whole-body lipids) − (initial weight × FA in initial whole-body × initial whole-body lipids))/(feed intake × dietary lipids × dietary FA) × 100.
Apparent digestibility coefficients (ADCs) for protein were used to calculate digestible protein in the two diets. This was based on the ADCs proposed by IAFFD Database (v4.1.2) for each of the protein sources used in each diet, and assuming additivity of the protein digestibility for each ingredient. Yttrium was included in the diets, but no in vivo fecal analysis was performed for this specific study.

2.4. Proximate Composition and Fatty Acid Analysis

The proximate composition analysis of feeds and whole-body fish samples followed the procedures described by AOAC [26]. Crude protein content (Nx6.25) was determined using the Kjeldahl method. Ash content was calculated through incineration at 600 °C for 12 h in a muffle furnace, while moisture content was determined by drying samples in an oven at 110 °C until reaching a constant weight. The total lipid content of the samples was extracted with chloroform/methanol (2:1 v/v) [27]. Then, fatty acid methyl esters were obtained by transmethylation of total lipids [28] and separated by gas chromatography following the conditions described by Izquierdo and co-authors [29]. Fatty acid methyl esters were quantified (in % of total fatty acids) by a flame ionization detector and identified by comparison with external and well-characterized FO standards (EPA 28, Nippai, Ltd., Tokyo, Japan). The amino acid profile of the diets was determined by EUROFINS food testing (Lisbon, Portugal).

2.5. Statistical Analysis

Data are expressed as mean ± SD and were tested for normality and homogeneity of variances through Shapiro–Wilk and Levene’s tests, respectively. To assess the impact of diet and feeding strategy, along with potential interactions, a two-way ANOVA was conducted. Significance was considered at p < 0.05. When significant interactions (p < 0.05) were detected between factors, a one-way ANOVA was employed, and Tukey’s post hoc test was applied to detect differences between groups. All statistical analyses were carried out using the SPSS Statistical Software System v24.0 (SPSS, Chicago, IL, USA).

3. Results

3.1. Zootechnical Performance

Diet had a significant effect on SGR of fish, with those fed the alternative diet displaying higher growth when compared to those fed the control diet (p < 0.05; Table 3). Furthermore, the alternative diet significantly increased PER, LER and protein retention in whole bodies of fish, and showed a tendency to also increase lipid retention, when compared with the control diet (p < 0.05; Table 4). In addition, feeding sea bass to apparent satiety (AS) led to higher growth due to the inherent increase in feed intake (p < 0.05; Table 3). However, AS led to the highest FCR and the lowest PER, LER and protein retention (p < 0.05; Table 4). The effects of diet and feeding strategy were independent since no significant interactions were found between the two factors for any productive parameter. In contrast, feeding restricted to 65% of apparent satiety led to lower feed conversion (p < 0.05; Table 3) and higher PER and LER (p < 0.05; Table 4) as well as higher protein retention, but also to lower growth (p < 0.05; Table 3), compared with 85% of apparent satiety.

3.2. Whole-Body Proximate Composition and Fatty Acid Profile

The whole-body proximate composition at the end of the feeding trial was similar among fish fed the different diets and the different feeding strategies (Table 5).
Fatty acid composition of fish whole bodies was mostly affected by the dietary treatment (Table 6). Fish fed the control diet showed significantly higher contents of 16:0, 16:1n-7, 16:1n-5, 16:2n-4, 17:0, 16:3n-4, 16:4n-3, 18:1n-7, 18:1n-5, 18:2n-9, 18:2n-4, 18:4n-3, 18:4n-1, 20:1n-5, 20:2n-9, 20:3n-9, 20:4n-3, 20:5n-3 and 22:5n-3, compared with those fed the alternative diet (p < 0.05; Table 6). In contrast, fish fed the alternative diet showed higher contents of 18:2n-6, 18:3n-3, 20:2n-6, 20:3n-3, 20:4n-6, 22:5n-6, 22:6n-3, n-6 and n-6 PUFA (p < 0.05; Table 6). Feeding strategy only significantly affected the contents of 20:1n-9, with feeding fish to 65% of apparent satiety leading to higher contents of this fatty acid compared to feeding at AS (p < 0.05; Table 6). No major significant diet × feeding interactions were observed.
The retentions of the different whole-body fatty acids were affected only by the dietary treatment (Table 7). Specifically, the control diet led to increased retention of certain fatty acids such as 14:1n-7, 15:1n-5, and 20:2n-6, while the alternative diet promoted higher retention of the fatty acids 16:1n-5, 17:0, 16:3n-4, 16:3n-16:4n-3, 18:2n-9, 18:3n-6, 18:4n-3, 20:2n-9, and 22:5n-3. No effects of feeding strategy or diet × feeding interactions were observed on the retention of the different fatty acids (Table 7).

4. Discussion

The adoption of novel feed formulations in aquaculture and optimizing feeding strategies to align with the composition of these novel feeds represent an important step to improve the performance as well as the environmental and economic sustainability of the industry [1,4,6]. The alternative diet, based on FM/FO substitution, significantly improved fish growth. These results suggest the effectiveness of the alternative diet formulation in promoting the growth performance of European sea bass juveniles, highlighting the potential of poultry by-products and novel feed ingredients such as IM and SCP as high-quality protein sources for this species. Indeed, although the higher growth rates observed in fish fed the alternative diet could be partially related to the higher crude protein content achieved in this diet, it should be noted that the digestible protein of the two diets is very similar. Although the diets were formulated to be iso-digestible (39% DP) based on established databases, the alternative diet contained a higher crude protein content (44.1% vs. 40.8%). While this was intended to compensate for the lower digestibility of alternative ingredients, we cannot exclude the possibility that a higher total protein intake contributed to the enhanced growth performance observed in the ALT group. Future studies should include in vivo digestibility trials to confirm if the observed benefits stem solely from the ingredient synergy or also from a higher-than-predicted protein availability. Still, in silico estimation of ADC-based IAFFD values is sound, and such an approach has been previously evaluated and validated in other studies [30]. In any case, these results clearly indicate that these novel sources can effectively meet the protein requirements of sea bass juveniles, even without essential amino acid supplementation to the diet. Moreover, it is noteworthy that the enhanced growth of fish with this alternative diet was not related to a higher feed intake, but rather an enhanced PER, which may also be related to a better-balanced amino acid profile. Such a better-balanced amino acid profile normally leads to a protein-sparing effect in fish [31]. It is likely that the alternative diet ultimately promoted a faster growth rate due to the higher availability of amino acids for protein synthesis [32].
These results also point out the high quality of the alternative lipid sources incorporated in this diet, including MO, PO and SO in replacement of FO. Indeed, these lipid sources might have also facilitated a better utilization of the dietary lipids by sea bass, contributing to further explaining the better LER and ultimately the growth in sea bass fed the alternative diet. It is also noteworthy that the alternative diet contained higher levels of some important fatty acids, such as DHA, probably associated with the dietary incorporation of the MO, which is rich in this essential fatty acid for marine carnivorous species like European sea bass [33]. DHA plays a key role in enhancing lipid metabolism and utilization, supporting various physiological functions such as membrane structure [34,35], and acting as a growth promoter in fish [33]. In agreement with our results, several studies have previously reported adequate growth in marine fish fed diets with the alternative and novel ingredients used in the alternative diet of the present study, with no adverse effects on growth performance of fish and feed utilization, namely poultry by-products [35,36,37,38] (reviewed by Galkanda-Arachchige and Davis [16]), insect meal (T. molitor) (reviewed by Shafique and co-authors [39]; Tran and co-authors [40]), bacterial single-cell protein meal (C. glutamicum) [41], or microalgae oils [42,43,44]. The simultaneous inclusion of such diverse novel alternatives in European sea bass diets was shown to bring similar performance for some of the feed formulations tested by Petereit and co-authors [15], but no clear benefits. Similar findings have been reported in turbot, where diets incorporating poultry meal, insect meal (Hermetia), salmon oil, and algae oil yielded comparable results [12], and in gilthead seabream, where insect (Hermetia) and C. glutamicum meals were tested [13]. In contrast, Pereira et al. [14] observed improved growth in rainbow trout under some alternative formulations.
Therefore, the present results reinforce the potential of those alternatives and novel ingredients in replacing the conventional marine ingredients (FM and FO) or soy protein sources, although the results may depend on fish species, inclusion levels in the diet, quality of the ingredient batches used, and the reference diet used for comparison in the studies.
In addition, the feeding strategy also significantly influenced the growth performance of fish. In this regard, feeding European sea bass to AS led to the highest feed intake and, consequently, the highest growth rate, but also negatively affected FCR, nutrient efficiency ratios (PER and LER) and protein retention compared to restricted feeding strategies. Therefore, these results suggest that, although an AS-feeding strategy can enhance growth, it is likely to increase feed needs and costs and reduce nutrient utilization and retention due to higher metabolic costs associated with an excessive feed intake [45] and generate higher waste of the dietary nutrients. Consequently, this may elevate production costs for farmers, as aquafeeds represent 40–70% of total production expenditures [46]. In agreement, Eroldoğan and co-authors [19] also observed that European sea bass grew more when fed at their full satiation level (100%), compared with lower daily satiation levels, namely 36%, 45%, 54%, 63%, and 71%. Moreover, these authors suggested an optimal daily feeding ratio falling between 54% and 63% of satiation level for improved feed conversion. Similarly, in our study, restricted feeding at 65% of satiation level led to lower FCR and higher nutrient efficiency ratios and protein retention, compared with AS or 85%, suggesting a more efficient utilization of the dietary nutrients. These results further agree with previous studies in other fish species that reported best feed efficiencies below the satiation point [24,47,48]. Indeed, the higher PER and protein retention observed in fish fed 65% might be indicative of a protein-sparing effect caused by restricted feeding ration. This is a compensatory mechanism in which fish tend to retain the protein by increasing the efficiency of protein utilization when energy intake is limited to ensure that the dietary protein is efficiently utilized for essential metabolic purposes rather than being used for energy production or wasted [49], explaining the observed higher protein retentions. However, in the present study, growth of fish fed at 65% was significantly reduced after 210 days, indicating that despite the higher protein efficiency and retention, this restricted feeding regimen failed at providing the necessary energy and nutrients for maintaining fish growth close to its maximum potential. In addition, PER, LER and protein retention were similar between fish fed at 85% and 65%, while higher growth was observed in those fed at 85% compared with 65%. Therefore, based on the present results, adopting an 85% strategy might be an intermediate reasonable strategy to optimize the balance between feed intake, growth, and nutrient utilization for European sea bass by improving nutrient efficiencies and protein retention without greatly compromising fish growth performance. However, due to other time-dependent costs in addition to feed (e.g., personnel, utilities, cage/tank maintenance), it cannot be said that this solution is the one that brings the most profitability to aquaculture operations. Hence, further studies aiming to compare a wide number of feeding strategies could be interesting to fine-tune the most cost-effective feeding strategies to ensure greater profitability of aquaculture operations in sea bass, as suggested for Nile tilapia [50].
It is noteworthy that, in the present study, the effects of diet and feeding strategy seemed to be independent, since no significant interactions were found between the two factors for any productive parameter, indicating that the observed effects of the diet on growth performance of sea bass were consistent regardless the different feeding strategies. This result is important because it further highlights the effectiveness of the alternative diet in promoting fish growth even under different feeding regimes. Furthermore, it also suggests that there were no interactions between the dietary protein level and feeding regimes, since control and alternative diets presented different crude protein contents. This is in line with what has been suggested in previous studies in fish [32,51]. Further research is needed to understand the individual response of this species, as some individuals are better adapted to periods of feed abundance, whereas others exhibit greater resilience to feed deprivation [52].
Despite the differences in some nutrient retentions and efficiencies, whole-body proximal composition of fish was similar among fish fed the different diets and fed at different feeding strategies, although a tendency to reduce whole-body lipid content when feeding restriction increases could be seen in either diet assayed, as the feeding restriction induced lower lipid levels [53]. However, whilst feeding strategy showed no significant effect on the fatty acid composition of sea bass whole bodies, the alternative diet notably favored the fatty acid profile of fish, increasing the contents of some important fatty acids for human health like alpha-linolenic acid (18:3n-3) and DHA, although it decreased those of EPA. These results suggests that the alternative diet, which incorporates alternative novel lipid sources like microalgae oil, effectively enriched the fish with these important fatty acids and thus could bring a higher nutritional value of fish final products to consumers. Conversely, fish fed the control diet showed higher levels of some saturated (16 and 17:0) and monounsaturated fatty acids (16:1n-7, 16:1n-5, 18:1n-7, 18:1n-5), which are fatty acids with lower nutritional value for consumers. In agreement with the present results, recently, other studies in Mediterranean farmed fish, including European sea bass [17,54], gilthead sea bream [42,55] and meagre [43], have also reported a beneficial effect of incorporating DHA-rich microalgal oils in the diet for enriching the fatty acid profile of fish tissues.
Furthermore, the observed differences in fatty acid retentions in whole bodies between fish fed the control and alternative diets highlight the significant impact of dietary composition on the fatty acid profile of fish whole bodies. These results suggest that the dietary fatty acid profile can influence the incorporation and retention of fatty acids in fish tissues, probably related to the different availability and metabolism of the dietary lipids, although diet did not significantly impact the retention of the most bioactive and essential fatty acids like ARA, EPA or DHA. In addition, although not statistically significant, a tendency towards increased retention of certain n-3 PUFAs such as 18:3n-3, 18:4n-3, 20:5n-3, and 22:6n-3, as well as some n-6 PUFAs like 20:4n-6, was observed with increasing feeding restriction. This suggests a selective retention of those essential fatty acids with important biological functions for fish, in response to the lower dietary availability due to the lower fatty acid intake in the restricted feeding strategies. Similarly, previous studies also found a selective retention of those essential fatty acids like EPA and DHA in several fish species, including in European sea bass [56], gilthead sea bream [57,58], turbot [59], Atlantic salmon [60], rainbow trout [61], Senegalese sole [62,63] and meagre [64].

5. Conclusions

The novel alternative diet evaluated in this study, formulated with a combination of poultry by-products, insect meal, and single-cell protein from Corynebacterium glutamicum as partial replacements for FM and soy proteins, together with a blend of alternative lipid sources (microalgal oil, salmon by-product oil, and poultry oil) substituting FO, resulted in significantly improved growth performance, nutrient utilization, and nutrient retention in European sea bass relative to a control diet composed of conventional ingredients (FM, FO, and soy products). In addition, the alternative diet positively influenced the whole-body fatty acid profile, particularly by increasing the levels of key fatty acids such as docosahexaenoic acid (DHA), thereby enhancing the nutritional quality of fish products for human consumption.

Author Contributions

Conceptualization, D.M., S.T. and L.E.C.C.; methodology, D.M. and R.G.; software, F.S.; validation, D.M.; formal analysis, M.C., F.S. and F.A.; investigation, D.M., M.C. and S.T.; resources, D.M., L.E.C.C. and R.G.; data curation, D.M., M.C., F.S. and R.G.; writing—original draft preparation, D.M. and M.C.; writing—review and editing, D.M., M.C., S.T., L.E.C.C., F.S. and R.G.; visualization, M.C.; supervision, D.M. and S.T.; project administration, D.M. and L.E.C.C.; funding acquisition, D.M. and L.E.C.C. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the European Union’s Horizon 2020 research and innovation program under grant agreement no. 818367; AquaIMPACT—Genomic and nutritional innovations for genetically superior farmed fish to improve efficiency in European aquaculture.

Institutional Review Board Statement

The animal experiments comply with the guidelines of the European Union Council (2010/63/EU) for the use of experimental animals. The Bioethical Committee of the University of Las Palmas de Gran Canaria approved all the protocols used in the present study (approval no OEBA-ULPGC-17-2021), approval date: 17 September 2021.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
ALTAlternative
ASApparent satiety
CControl
DHADocosahexaenoic acid (22:6-n3)
EPAEicosapentaenoic acid (20:5n-3)
FCRFeed conversion ratio
FMFishmeal
FOFish oil
IMInsect meal
LC-PUFALong-chain polyunsaturated fatty acid
LERLipid efficiency ratio
MOMicroalgae
PBMPoultry by-product meal
PERProtein efficiency ratio
PMPoultry meal
POPoultry oil
SOSalmon oil
SGRSpecific growth rate
WGWeight gain

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Table 1. Feed formulation (%) and proximate composition (% dry matter) of experimental diets for European sea bass.
Table 1. Feed formulation (%) and proximate composition (% dry matter) of experimental diets for European sea bass.
Ingredients (%)Control (C)
4 mm		Alternative (ALT) 4 mm
Fishmeal Super Prime 120.0010.00
Porcine blood meal 20.002.00
Poultry meal 30.0015.00
Worm meal (Tenebrio) 40.007.00
Aminopro NT70-C. glutamicum 50.004.00
Soy protein concentrate 615.0010.60
Wheat gluten 710.304.40
Corn gluten meal 85.005.00
Soybean meal 48 96.004.50
Wheat meal 1016.4810.98
Faba beans (low tannins) 118.008.00
Vit and Min Premix *1.001.00
Antioxidant 120.200.20
MCP 130.520.52
Rapeseed lecithin liquid 142.002.50
Fish oil 157.500.00
Salmon oil 160.002.50
Algae oil 170.003.00
Rapeseed oil 188.006.80
Poultry fat0.002.00
Yttrium Oxide0.020.02
Proximate composition (% dry matter)
Crude protein40.844.1
Digestible Protein 1938.739.3
Crude fat20.020.0
Ash6.87.6
Gross Energy (MJ/kg feed)22.022.3
1—Diamante, Pesquera Diamante, San Isidro, Peru. 2—SONAC BV, Eindhoven, The Netherlands. 3—SAVINOR UTS, Covelas, Portugal. 4—Entomo, Bourgon, France. 5—MAZZOLENI SPA, Bergamo, Italy. 6—ADM, Amsterdam, The Netherlands. 7—Roquette, Lestrem, France. 8—COPAM, São João da Talha, Portugal. 9—Ribeiro & Sousa Lda, Paredes, Portugal. 10—Molisur, Malaga, Spain. 11—Ribeiro & Sousa Lda, Portugal. 12—VERDILOX, Kemin Europe NV, Herentals, Belgium. 13—ALIPHOS, Ottignies-Louvain-la-Neuve, Belgium. 14—Novastell, Vernon, France. 15—Sopropêche, Wimille, France. 16—Sopropêche, France. 17—Allmicroalgae, Pataias, Portugal. 18—JC Coimbra, Setúbal, Portugal. *—Vitamins (IU or mg/Kg diet): DL-alphatocopherol acetate, 100 mg; sodium menadione bisulphate, 25 mg; retinyl acetate, 20,000 IU; DL-cholecalciferol, 2000 IU; thiamine, 30 mg; riboflavin, 30 mg; pyridoxine, 20 mg; cyanocobalamin, 0.1 mg; nicotidin acid, 200 mg; folic acid, 15 mg; ascorbic acid, 1000 mg; inositol, 500 mg; biotin, 3 mg; calcium panthotenate, 100 mg; choline chloride, 1000 mg, betaine, 500 mg. Minerals (g or mg/kg diet): cobalt carbonate, 0.65 mg; copper sulphate, 9 mg; ferric sulphate, 6 mg; potassium iodide, 0.5 mg; manganese oxide, 9.6 mg; sodium selenite, 0.01 mg; zinc sulphate, 7.5 mg; sodium chloride, 400 mg; calcium carbonate, 1.86 g; excipient wheat middling. 19—Using apparent digestibility coefficients (ADCs) proposed by IAFFD Database (v4.1.2) for each of the protein sources, and assuming additivity of the protein digestibility for each ingredient.
Table 2. Amino acid (in g/100 g) and fatty acid (in % total identified fatty acids) profiles of the experimental diets for European sea bass.
Table 2. Amino acid (in g/100 g) and fatty acid (in % total identified fatty acids) profiles of the experimental diets for European sea bass.
Amino Acids
(g/100 g)		C 4 mmALT 4 mmFatty Acids
(g/100 g FA Identified)		C 4 mmALT 4 mm
Alanine1.93 ± 0.272.47 ± 0.3514:00.620.45
Arginine2.20 ± 0.312.63 ± 0.3714:1n-70.000.01
Aspartic acid3.35 ± 0.473.71 ± 0.5214:1n-50.020.01
Glutamic acid8.60 ± 1.207.69 ± 1.0815:000.090.18
Glycine1.78 ± 0.252.83 ± 0.4015:1n-50.000.01
Histidine1.03 ± 0.141.01 ± 0.1416:0ISO0.020.01
Hydroxyproline0.20 ± 0.020.44 ± 0.0916:07.4810.24
Isoleucine1.60 ± 0.221.71 ± 0.2416:1n-72.471.27
Leucine3.15 ± 0.443.56 ± 0.5016:1n-50.120.03
Lysine2.59 ± 0.362.55 ± 0.3616:2n-60.010.00
Phenylalanine1.86 ± 0.261.95 ±0.2716:2n-40.300.05
Proline2.67 ± 0.372.77 ± 0.3917:00.300.05
Serine1.83 ± 0.262.04 ± 0.2916:3n-40.110.07
Threonine1.47 ± 0.212.02 ± 0.2816:3n-30.070.03
Tyrosine1.35 ± 0.191.43 ± 0.2016:3n-10.030.03
Valine1.83 ± 0.262.07 ± 0.2916:4n-30.550.06
Cysteine 0.57 ± 0.080.61 ± 00816:4n-10.010.01
Methionine0.71 ± 0.090.75 ± 0.1118:03.153.32
Tryptophane0.47 ± 0.050.49 ± 0.0518:1n-932.7433.99
18:1n-73.302.25
18:1n-50.060.05
18:2n-90.090.02
18:2n-615.0617.68
18:2n-40.220.05
18:3n-60.120.08
18:3n-40.090.05
18:3n-34.083.75
18:3n-10.090.05
18:4n-31.060.25
18:4n-10.140.04
20:000.740.53
20:1n-90.100.11
20:1n-71.931.67
20:1n-50.230.11
20:2n-90.170.04
20:2n-60.160.37
20:3n-90.040.01
20:3n-60.110.14
20:4n-60.820.93
20:3n-30.070.17
20:4n-30.560.40
20:5n-311.935.30
22:1n-110.510.69
22:1n-90.650.49
22:4n-60.070.14
22:5n-60.220.70
22:5n-31.550.91
22:6n-37.7213.19
SFA12.4014.78
MUFA42.1340.68
n-3 PUFA27.0424.00
n-6 PUFA16.5720.05
EPA + DHA 19.6618.49
C, control diet; ALT, alternative diet; SFA, Saturated fatty acids.
Table 3. Performance parameters of European sea bass fed the experimental diets and different feeding strategies for 210 days.
Table 3. Performance parameters of European sea bass fed the experimental diets and different feeding strategies for 210 days.
DietFeedingWeight (g)T. Length (cm)KWG (g)SGRFCRFI (g Fish −1)
CAS230.13 ± 7.8826.06 ± 0.211.30 ± 0.02201.66 ± 7.820.99 ± 0.021.28 ± 0.02257.15 ± 9.83
85%210.35 ± 2.4925.31 ± 0.211.30 ± 0.05181.88 ± 3.030.95 ± 0.021.17 ± 0.04212.95 ± 9.35
65%179.10 ± 8.7524.39 ± 0.531.23 ± 0.04151.41 ± 8.510.89 ± 0.021.11 ± 0.05167.88 ± 6.15
ALTAS240.16 ± 11.5426.57 ± 0.701.28 ± 0.05211.45 ± 10.621.01 ± 0.011.26 ± 0.02265.18 ± 9.45
85%223.34 ± 10.3325.95 ± 0.301.28 ± 0.04195.32 ± 9.620.99 ± 0.011.16 ± 0.02225.85 ± 10.53
65%182.15 ± 4.7224.54 ± 0.241.23 ± 0.02154.03 ± 4.640.89 ± 0.011.10 ± 0.04169.88 ± 3.99
Dietp = 0.03
ALT > C		n.s.n.s.n.s.p = 0.04
ALT > C		n.s.n.s.
Two-way ANOVAFeeding strategyp < 0.001
AS > 85% > 65%		p < 0.001
AS = 85% > 65%		n.s.p < 0.001
AS > 85% > 65%		p < 0.001
AS > 85% > 65%		p < 0.001
AS > 85% > 65%		p < 0.001
AS > 85% > 65%
DxFn.s.n.s.n.s.n.s.n.s.n.s.n.s.
C, control diet; ALT, alternative diet; AS, apparent satiety; 85%, 85% of apparent satiety; 65%, 65% of apparent satiety; n.s., not significant.
Table 4. Nutrient efficiency ratios and retentions of European sea bass fed the experimental diets and different feeding strategies.
Table 4. Nutrient efficiency ratios and retentions of European sea bass fed the experimental diets and different feeding strategies.
DietFeedingPERLERProtein Retention (%)Lipid Retention (%)
CAS1.50 ± 0.025.09 ± 0.0824.18 ± 0.3592.01 ± 11.38
85%1.63 ± 0.035.53 ± 0.1225.20 ± 0.5094.60 ± 12.49
65%1.71 ± 0.065.80 ± 0.2227.24 ± 1.1994.59 ± 2.86
ALTAS1.64 ± 0.024.70 ± 0.0625.84 ± 1.0580.66 ± 6.90
85%1.79 ± 0.065.12 ± 0.01727.97 ± 0.7991.52 ± 15.90
65%1.89 ± 0.085.40 ± 0.2328.99 ± 0.7998.22 ± 14.73
Two-way ANOVADietp = 0.000
ALT > C		p = 0.000
ALT > C		p = 0.019
ALT > C		n.s.
Feeding strategyp < 0.001
65% > AS		p < 0.001
65% > AS		p = 0.048
65% > AS		n.s.
DxFn.s.n.s.n.s.n.s.
C, control diet; ALT, alternative diet; AS, apparent satiety; 85%, 85% of apparent satiety; 65%, 65% of apparent satiety; n.s., not significant.
Table 5. Biochemical composition (% wet weight) of whole body of European sea bass fed the experimental diets and different feeding strategies.
Table 5. Biochemical composition (% wet weight) of whole body of European sea bass fed the experimental diets and different feeding strategies.
DietFeeding StrategyProteinAshLipidsMoisture
AS15.39 ± 0.391.25 ± 0.1316.44 ± 1.4265.86 ± 0.76
Control85%15.27 ± 0.611.19 ± 0.0916.99 ± 2.7065.40 ± 1.56
65%14.98 ± 0.231.10 ± 0.1315.44 ± 1.7666.32 ± 1.20
AS15.72 ± 0.121.22 ± 0.1017.25 ± 2.0165.52 ± 0.89
ALT85%15.14 ± 0.291.18 ± 0.0316.34 ± 1.6765.73 ± 0.94
65%15.47 ± 0.491.09 ± 0.2215.54 ± 0.7466.93 ± 0.61
Control, control diet; ALT, alternative diet; AS, apparent satiety; 85%, 85% of apparent satiety; 65%, 65% of apparent satiety.
Table 6. Fatty acid (% total fatty acids) of whole bodies of European sea bass fed the experimental diets and different feeding strategies.
Table 6. Fatty acid (% total fatty acids) of whole bodies of European sea bass fed the experimental diets and different feeding strategies.
Fatty AcidsC-ASC-85%C-65%ALT-ASALT-85%ALT-65%Two-Way ANOVA
(p-Value)
DietFDxF
14:00.36 ± 0.290.78 ± 0.950.46 ± 0.220.39 ± 0.130.29 ± 0.340.33 ± 0.34n.s.n.s.n.s.
14:1n-70.01 ± 0.000.02 ± 0.010.01 ± 0.000.01 ± 0.000.01 ± 0.000.02 ± 0.00n.s.n.s.n.s.
14:1n-50.02 ± 0.000.04 ± 0.030.02 ± 0.000.01 ± 0.000.01 ± 0.000.02 ± 0.01n.s.n.s.n.s.
15:00.06 ± 0.050.12 ± 0.080.10 ± 0.050.14 ± 0.050.11 ± 0.090.13 ± 0.10n.s.n.s.n.s.
15:1n-50.01 ± 0.000.02 ± 0.000.02 ± 0.000.01 ± 0.000.01 ± 0.000.02 ± 0.00n.s.n.s.n.s.
16:0ISO0.02 ± 0.000.02 ± 0.010.02 ± 0.000.01 ± 0.000.01 ± 0.000.02 ± 0.00p < 0.01
C > ALT		n.s.n.s.
16:07.62 ± 2.4811.16 ± 2.6510.10 ± 2.7010.77 ± 2.749.31 ± 3.539.30 ± 3.68n.s.n.s.n.s.
16:1n-71.98 ± 0.793.31 ± 1.092.71 ± 0.861.78 ± 0.521.59 ± 0.721.55 ± 0.71p < 0.01
C > ALT		n.s.n.s.
16:1n-50.06 ± 0.010.09 ± 0.020.08 ± 0.020.04 ± 0.010.04 ± 0.010.04 ± 0.01p <0.01
C > ALT		n.s.n.s.
16:2n-60.01 ± 0.000.10 ± 0.120.02 ± 0.010.02 ± 0.010.02 ± 0.000.01 ± 0.00n.s.n.s.n.s.
16:2n-40.15 ± 0.060.35 ± 0.170.22 ± 0.070.06 ± 0.020.07 ± 0.040.06 ± 0.02p < 0.01
C > ALT		n.s.n.s.
17:00.12 ± 0.060.22 ± 0.090.17 ± 0.060.04 ± 0.010.05 ± 0.020.04 ± 0.01p < 0.01
C > ALT		n.s.n.s.
16:3n-40.13 ± 0.020.16 ± 0.010.16 ± 0.010.12 ± 0.020.12 ± 0.020.12 ± 0.03p = 0.02
C > ALT		n.s.n.s.
16:3n-30.07 ± 0.02 a0.05 ± 0.00 a0.06 ± 0.01 a0.02 ± 0.00 b0.03 ± 0.00 b0.03 ± 0.00 bp < 0.01
C > ALT		n.s.p = 0.03
16:3n-10.03 ± 0.010.03 ± 0.020.04 ± 0.000.03 ± 0.010.03 ± 0.000.03 ± 0.01n.s.n.s.n.s.
16:4n-30.15 ± 0.080.27 ± 0.110.20 ± 0.080.04 ± 0.010.06 ± 0.020.06 ± 0.01p < 0.01
C > ALT		n.s.n.s.
16:4n-10.02 ± 0.010.17 ± 0.170.02 ± 0.010.03 ± 0.020.02 ± 0.010.02 ± 0.01n.s.n.s.n.s.
18:03.84 ± 0.425.79 ± 4.063.63 ± 0.455.40 ± 3.605.36 ± 3.294.82 ± 2.60n.s.n.s.n.s.
18:1n-939.10 ± 1.5335.76 ± 5.7338.26 ± 1.3537.75 ± 2.7138.11 ± 3.6737.02 ± 2.85n.s.n.s.n.s.
18:1n-73.22 ± 0.482.55 ± 1.103.20 ± 0.791.91 ± 0.932.00 ± 0.941.86 ± 0.56p = 0.02
C > ALT		n.s.n.s.
18:1n-50.11 ± 0.040.10 ± 0.020.13 ± 0.040.09 ± 0.030.07 ± 0.010.07 ± 0.01p = 0.02
C > ALT		n.s.n.s.
18:2n-90.47 ± 0.040.52 ± 0.050.46 ± 0.050.35 ± 0.000.33 ± 0.030.27 ± 0.09p < 0.01
C > ALT		n.s.n.s.
18:2n-613.26 ± 0.4813.32 ± 0.2713.78 ± 0.3915.37 ± 0.3515.59 ± 0.2515.90 ± 0.53p < 0.01
ALT > C		n.s.n.s.
18:2n-40.19 ± 0.000.19 ± 0.020.19 ± 0.030.06 ± 0.010.07 ± 0.000.06 ± 0.01p < 0.01
C > ALT		n.s.n.s.
18:3n-60.19 ± 0.020.22 ± 0.030.22 ± 0.020.20 ± 0.010.20 ± 0.020.20 ± 0.02n.s.n.s.n.s.
18:3n-40.11 ± 0.010.12 ± 0.070.17 ± 0.090.05 ± 0.020.07 ± 0.010.08 ± 0.03n.s.n.s.n.s.
18:3n-33.58 ± 0.083.57 ± 0.163.67 ± 0.083.70 ± 0.073.73 ± 0.033.81 ± 0.13p < 0.01
ALT > C		n.s.n.s.
18:3n-10.08 ± 0.000.09 ± 0.030.13 ± 0.080.07 ± 0.000.07 ± 0.000.07 ± 0.00n.s.n.s.n.s.
18:4n-30.76 ± 0.010.80 ± 0.040.82 ± 0.050.27 ± 0.020.30 ± 0.040.31 ± 0.03p < 0.01
C > ALT		n.s.n.s.
18:4n-10.10 ± 0.000.12 ± 0.010.14 ± 0.040.03 ± 0.000.04 ± 0.010.03 ± 0.00p < 0.01
C > ALT		n.s.n.s.
20:00.44 ± 0.060.36 ± 0.070.37 ± 0.060.33 ± 0.050.36 ± 0.070.36 ± 0.07n.s.n.s.n.s.
20:1n-90.09 ± 0.010.15 ± 0.090.18 ± 0.030.09 ± 0.020.13 ± 0.010.15 ± 0.05n.s.p = 0.04
65% > AS		n.s.
20:1n-72.56 ± 0.302.03 ± 0.432.07 ± 0.282.20 ± 0.302.29 ± 0.392.40 ± 0.40n.s.n.s.n.s.
20:1n-50.19 ± 0.030.18 ± 0.070.19 ± 0.050.10 ± 0.020.11 ± 0.030.11 ± 0.02p < 0.01
C > ALT		n.s.n.s.
20:2n-90.15 ± 0.020.15 ± 0.030.16 ± 0.030.06 ± 0.010.07 ± 0.010.07 ± 0.01p < 0.01
C > ALT		n.s.n.s.
20:2n-60.71 ± 0.070.56 ± 0.120.62 ± 0.040.75 ± 0.100.78 ± 0.120.82 ± 0.11p < 0.01
ALT > C		n.s.n.s.
20:3n-90.06 ± 0.030.04 ± 0.020.08 ± 0.030.02 ± 0.000.02 ± 0.000.03 ± 0.02p < 0.01
C > ALT		n.s.n.s.
20:3n-60.14 ± 0.040.12 ± 0.020.17 ± 0.060.14 ± 0.020.14 ± 0.020.16 ± 0.04n.s.n.s.n.s.
20:4n-60.68 ± 0.040.57 ± 0.080.59 ± 0.060.72 ± 0.090.73 ± 0.110.77 ± 0.11p < 0.01
p < 0.01
ALT > C		n.s.n.s.
20:3n-30.09 ± 0.010.07 ± 0.010.14 ± 0.070.13 ± 0.020.16 ± 0.040.16 ± 0.03p < 0.01
ALT > C		n.s.n.s.
20:4n-30.47 ± 0.050.40 ± 0.060.45 ± 0.110.32 ± 0.050.34 ± 0.050.36 ± 0.07p < 0.01
C > ALT		n.s.n.s.
20:5n-38.70 ± 0.957.46 ± 1.167.31 ± 0.853.98 ± 0.514.39 ± 0.534.33 ± 0.75p < 0.01
C > ALT		n.s.n.s.
22:1n-110.32 ± 0.030.27 ± 0.050.32 ± 0.000.33 ± 0.080.37 ± 0.070.44 ± 0.10p = 0.03n.s.n.s.
22:1n-90.49 ± 0.060.41 ± 0.060.49 ± 0.080.39 ± 0.090.43 ± 0.080.45 ± 0.13n.s.n.s.n.s.
22:4n-60.07 ± 0.010.06 ± 0.010.14 ± 0.100.11 ± 0.020.12 ± 0.030.12 ± 0.03n.s.n.s.n.s.
22:5n-60.22 ± 0.010.19 ± 0.040.29 ± 0.060.60 ± 0.260.53 ± 0.130.58 ± 0.15p < 0.01
ALT > C		n.s.n.s.
22:5n-31.43 ± 0.241.16 ± 0.251.29 ± 0.080.90 ± 0.170.98 ± 0.171.05 ± 0.30p < 0.01
C > ALT		n.s.n.s.
22:6n-37.34 ± 0.665.75 ± 1.205.92 ± 0.7510.08 ± 2.1310.32 ± 2.0411.37 ± 2.68p < 0.01
ALT > C		n.s.n.s.
SFA12.44 ± 2.4718.42 ± 7.6214.83 ± 2.5517.08 ± 6.3215.49 ± 7.2114.98 ± 6.65n.s.n.s.n.s.
MUFA48.16 ± 1.5244.93 ± 6.0447.67 ± 1.2644.72 ± 3.5545.17 ± 4.4044.14 ± 3.18n.s.n.s.n.s.
n-940.36 ± 1.6037.03 ± 5.8039.64 ± 1.4138.66 ± 2.7639.08 ± 3.7837.99 ± 3.08n.s.n.s.n.s.
n-615.29 ± 0.4215.14 ± 0.3415.83 ± 0.5117.89 ± 0.5818.11 ± 0.5318.56 ± 0.35p < 0.01
ALT > C		n.s.n.s.
n-322.60 ± 1.6919.54 ± 2.6919.87 ± 1.4619.43 ± 2.8220.32 ± 2.8021.48 ± 3.75n.s.n.s.n.s.
n-6 PUFA15.29 ± 0.4215.14 ± 0.3415.83 ± 0.5117.89 ± 0.5818.11 ± 0.5318.56 ± 0.35p < 0.01
ALT > C		n.s.n.s.
n-3 PUFA22.53 ± 1.7119.49 ± 2.6919.81 ± 1.4619.41 ± 2.8220.29 ± 2.8021.45 ± 3.75n.s.n.s.n.s.
EPA + DHA16.05 ± 1.5213.22 ± 2.2913.23 ± 1.5314.05 ± 2.6314.72 ± 2.5615.71 ± 3.41n.s.n.s.n.s.
EPA/ARA12.76 ± 0.6913.04 ± 0.5112.33 ± 0.365.56 ± 0.055.99 ± 0.165.61 ± 0.23p < 0.01
C > ALT		n.s.n.s.
EPA/DHA1.18 ± 0.081.31 ± 0.141.24 ± 0.080.40 ± 0.030.43 ± 0.030.38 ± 0.03p < 0.01
C > ALT		n.s.n.s.
Different letters denote significant differences among the treatments for a specific interaction (p < 0.05). AS, apparent satiety; 85%, 85% of apparent satiety; 65%, 65% of apparent satiety; C, control diet; ALT, alternative diet; n.s., not significant.
Table 7. Fatty acid retentions (% fatty acid intake) of whole bodies of European sea bass fed the experimental diets and different feeding strategies.
Table 7. Fatty acid retentions (% fatty acid intake) of whole bodies of European sea bass fed the experimental diets and different feeding strategies.
Fatty AcidsC-ASC-85%C-65%ALT-ASALT-85%ALT-65%Two-Way ANOVA (p-Value)
DietFDxF
14:032.6 ± 34.894.2 ± 125.056.5 ± 36.159.9 ± 17.038.8 ± 73.640.8 ± 77.1n.s.n.s.n.s.
14:1n-7165.8 ± 40.7324.7 ± 114.9265.5 ± 144.075.9 ± 8.290.7 ± 27.8135.1 ± 30.2p = 0.002
C > ALT		n.s.n.s.
14:1n-532.8 ± 1.2128.8 ± 109.167.4 ± 25.021.1 ± 7.042.5 ± 20.165.4 ± 53.6n.s.n.s.n.s.
15:035.7 ± 35.799.1 ± 64.381.5 ± 49.367.6 ± 20.552.3 ± 48.759.7 ± 57.7n.s.n.s.n.s.
15:1n-5189.6 ± 46.9329.9 ± 42.7314.6 ± 130.588.9 ± 12.5106.8 ± 24.0143.9 ± 19.3p < 0.001
C > ALT		n.s.n.s.
16:0ISO50.9 ± 16.599.2 ± 58.292.5 ± 35.741.0 ± 6.759.2 ± 5.764.4 ± 33.5n.s.n.s.n.s.
16:072.5 ± 20.2129.6 ± 34.6121.3 ± 28.691.8 ± 21.879.8 ± 33.177.7 ± 34.3n.s.n.s.n.s.
16:1n-755.1 ± 20.8115.0 ± 33.696.0 ± 29.5109.3 ± 28.995.5 ± 53.185.4 ± 54.1n.s.n.s.n.s.
16:1n-534.6 ± 3.863.3 ± 13.754.8 ± 9.1109.6 ± 51.389.6 ± 46.776.1 ± 40.4p = 0.024
ALT > C		n.s.n.s.
16:2n-440.6 ± 13.1106.3 ± 38.172.0 ± 17.282.4 ± 27.6104.6 ± 65.988.5 ± 39.3n.s.n.s.n.s.
17:032.9 ± 13.566.5 ± 19.255.7 ± 16.380.2 ± 20.892.0 ± 48.079.1 ± 29.9p = 0.028
ALT > C		n.s.n.s.
16:3n-481.9 ± 9.0116.0 ± 22.7124.4 ± 19.8150.0 ± 29.8142.3 ± 43.8142.6 ± 35.4p = 0.018
ALT > C		n.s.n.s.
16:3n-372.8 ± 12.759.6 ± 15.683.1 ± 17.943.3 ± 16.570.9 ± 7.656.6 ± 14.4n.s.n.s.n.s.
16:3n-159.6 ± 27.366.4 ± 46.974.4 ± 17.152.3 ± 28.865.3 ± 19.830.2 ± 42.5n.s.n.s.n.s.
16:4n-322.5 ± 10.245.6 ± 12.037.4 ± 10.756.4 ± 6.782.0 ± 36.479.1 ± 12.9p < 0.001
ALT > C		n.s.n.s.
16:4n-1146.7 ± 90.81438.2 ± 1324.6219.4 ± 64.6241.7 ± 162.0190.9 ± 52.1170.5 ± 63.2n.s.n.s.n.s.
18:0097.2 ± 19.5160.5 ± 95.1110.7 ± 31.5143.6 ± 82.2152.8 ± 95.3136.8 ± 76.8n.s.n.s.n.s.
18:1n-998.0 ± 13.1102.5 ± 35.6117.0 ± 24.4104.1 ± 22.9108.1 ± 25.3104.8 ± 12.4n.s.n.s.n.s.
18:1n-781.4 ± 19.575.6 ± 50.8100.8 ± 43.680.3 ± 51.185.0 ± 54.776.2 ± 28.6n.s.n.s.n.s.
18:1n-5136.3 ± 48.4161.1 ± 72.3227.0 ± 115.8170.9 ± 94.9116.8 ± 36.1100.5 ± 30.6n.s.n.s.n.s.
18:2n-9418.0 ± 81.4527.1 ± 106.2506.8 ± 156.71668.3 ± 266.81615.8 ± 396.41216.7 ± 559.2p < 0.001
ALT > C		n.s.n.s.
18:2n-670.0 ± 5.280.2 ± 18.989.3 ± 19.480.3 ± 14.183.9 ± 14.985.6 ± 3.2n.s.n.s.n.s.
18:2n-472.4 ± 6.782.9 ± 21.690.3 ± 27.599.2 ± 35.1112.8 ± 23.095.0 ± 21.7n.s.n.s.n.s.
18:3n-6105.5 ± 7.0140.9 ± 11.6149.1 ± 51.3191.5 ± 17.5194.9 ± 24.7193.1 ± 23.5p < 0.001
ALT > C		n.s.n.s.
18:3n-4100.2 ± 2.1122.2 ± 53.9197.3 ± 110.783.3 ±
43.6		112.0 ± 28.2138.8 ± 65.4n.s.n.s.n.s.
18:3n-372.6 ± 7.582.4 ± 18.191.3 ± 17.793.0 ± 15.496.7 ± 15.099.9 ± 5.8n.s.n.s.n.s.
18:3n-173.6 ± 9.099.9 ± 33.3157.3 ± 87.9119.9 ± 19.3127.4 ± 24.7127.8 ± 6.2n.s.n.s.n.s.
18:4n-360.0 ± 6.672.4 ± 18.579.4 ± 14.487.5 ± 7.2101.4 ± 11.1106.9 ± 13.8p < 0.001
ALT > C		n.s.n.s.
18:4n-162.3 ± 8.182.0 ± 24.1105.8 ± 36.960.4 ± 6.997.7 ± 41.771.4 ± 5.8n.s.n.s.n.s.
20:0050.0 ± 11.145.6 ± 14.050.6 ± 16.659.2 ± 13.765.7 ± 16.266.0 ± 16.7n.s.n.s.n.s.
20:1n-958.5 ± 19.7128.2 ± 125.1159.3 ± 55.061.7 ± 11.196.9 ± 26.4120.2 ± 49.9n.s.n.s.n.s.
20:1n-7107.0 ± 24.192.9 ± 30.8101.2 ± 27.5119.4 ± 30.9127.4 ± 33.0133.7 ± 29.6n.s.n.s.n.s.
20:1n-565.5 ± 19.172.9 ± 45.680.0 ± 38.381.7 ± 27.087.4 ± 43.189.2 ± 25.2n.s.n.s.n.s.
20:2n-970.1 ± 16.580.6 ± 35.488.6 ± 25.9118.3 ± 36.2138.2 ± 37.8133.0 ± 42.8p = 0.008
ALT > C		n.s.n.s.
20:2n-6346.1 ± 72.5302.3 ± 108.7363.8 ± 91.2183.8 ± 47.8197.1 ± 49.3207.2 ± 37.3p = 0.001
C > ALT		n.s.n.s.
20:3n-9106.9 ± 54.296.9 ± 60.7197.9 ± 99.3123.9 ± 46.0111.6 ± 41.0196.6 ± 160.0n.s.n.s.n.s.
20:3n-698.3 ± 22.589.3 ± 44.1152.2 ± 76.283.5 ± 23.585.4 ± 22.5100.6 ± 32.4n.s.n.s.n.s.
20:4n-666.6 ± 11.061.9 ± 15.569.2 ± 17.170.9 ± 16.174.5 ± 15.579.0 ± 15.4n.s.n.s.n.s.
20:3n-387.4 ± 18.576.1 ± 24.3184.6 ± 100.671.3 ± 18.789.8 ± 37.786.0 ± 21.0n.s.n.s.n.s.
20:4n-370.0 ± 15.166.6 ± 17.382.3 ± 36.771.6 ± 17.279.9 ± 17.184.3 ± 20.0n.s.n.s.n.s.
20:5n-362.6 ± 12.660.6 ± 15.664.3 ± 16.670.5 ± 15.680.3 ± 15.680.1 ± 17.5n.s.n.s.n.s.
22:1n-1141.2 ± 9.836.4 ± 12.047.4 ± 12.036.6 ± 12.643.1 ± 11.950.8 ± 17.8n.s.n.s.n.s.
22:1n-962.3 ± 14.557.6 ± 18.376.0 ± 27.771.8 ± 22.283.1 ± 24.286.2 ± 30.0n.s.n.s.n.s.
22:4n-681.7 ± 21.476.0 ± 28.2203.9 ± 154.972.7 ± 21.185.2 ± 33.082.9 ± 24.0n.s.n.s.n.s.
22:5n-679.8 ± 12.176.6 ± 23.7130.0 ± 39.282.6 ± 37.874.2 ± 18.383.7 ± 24.4n.s.n.s.n.s.
22:5n-378.4 ± 19.870.5 ± 17.586.5 ± 17.194.4 ± 29.5104.7 ± 23.7114.8 ± 37.8p = 0.049
ALT > C		n.s.n.s.
22:6n-378.3 ± 14.667.2 ± 16.474.9 ± 16.673.0 ± 20.076.4 ± 16.386.7 ± 23.9n.s.n.s.n.s.
AS, apparent satiety; 85%, 85% of apparent satiety; 65%, 65% of apparent satiety; C, control diet; ALT, alternative diet; n.s., not significant.
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Montero, D.; Carvalho, M.; Torrecillas, S.; Conceição, L.E.C.; Soares, F.; Acosta, F.; Ginés, R. Redesigning Aquafeeds: Insect, Algae, and By-Product Blends Sustain Growth and Nutritional Value in European Sea Bass Under Feeding Constraints. Fishes 2026, 11, 75. https://doi.org/10.3390/fishes11020075

AMA Style

Montero D, Carvalho M, Torrecillas S, Conceição LEC, Soares F, Acosta F, Ginés R. Redesigning Aquafeeds: Insect, Algae, and By-Product Blends Sustain Growth and Nutritional Value in European Sea Bass Under Feeding Constraints. Fishes. 2026; 11(2):75. https://doi.org/10.3390/fishes11020075

Chicago/Turabian Style

Montero, Daniel, Marta Carvalho, Silvia Torrecillas, Luís E. C. Conceição, Filipe Soares, Félix Acosta, and Rafael Ginés. 2026. "Redesigning Aquafeeds: Insect, Algae, and By-Product Blends Sustain Growth and Nutritional Value in European Sea Bass Under Feeding Constraints" Fishes 11, no. 2: 75. https://doi.org/10.3390/fishes11020075

APA Style

Montero, D., Carvalho, M., Torrecillas, S., Conceição, L. E. C., Soares, F., Acosta, F., & Ginés, R. (2026). Redesigning Aquafeeds: Insect, Algae, and By-Product Blends Sustain Growth and Nutritional Value in European Sea Bass Under Feeding Constraints. Fishes, 11(2), 75. https://doi.org/10.3390/fishes11020075

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