A plant-based diet supplemented with Hermetia illucens alone or in combination with poultry by-product meal: one step closer to sustainable aquafeeds for European seabass

Abstract

Background Increasing demand for high-value fish species and pressure on forage fish is challenging aquaculture to ensure sustainable growth by replacing protein sources in aquafeeds with plant and terrestrial animal proteins, without compromising the economic value and quality of the final fish product. In the present study, the effects of a plant protein-based diet (CV), two plant-based diets in which graded amounts of plan protein mixtures were replaced with Hermetia illucens meal alone (VH10) or in combination with poultry by-product meal (PBM) (VH10P30), a fishmeal (FM) diet (CF) and an FM diet supplemented with H. illucens (FH10) on growth performance, gut health and homeostasis of farmed subadult European seabass were tested and compared. Results Fish fed the VH10 and VH10P30 diets showed the highest specific growth rates and lowest feed conversion ratios among the tested groups. Expectedly, the best preservation of PI morphology was observed in fish fed the CF or FH10 diets, while fish fed the CV diet exhibited significant degenerative changes in the proximal and distal intestines. However, PBM supplementation mitigated these effects and significantly improved all gut morphometric parameters in the VH10P30 group. Partial substitution of the plant mixture with insect meal alone or PBM also induced most BBM genes and activated BBM enzymes, suggesting a beneficial effect on intestinal digestive/absorption functions. Regarding intestinal microbiota, fish fed diets containing H. illucens meal (FH10, VH10, VH10P30) had the highest richness of bacterial communities and abundance of beneficial genera such as Lactobacillus and Bacillus. On the other hand, fish fed CV had the highest microbial diversity but lost a significant component of fish intestinal microbiota, the phylum Bacteroidetes. Finally, skin pigmentation most similar to that of farmed or even wild seabass was also observed in the fish groups fed CF, FH10 or VH10P30. Conclusion Plant-based diets supplemented with PBM and H. illucens pupae meal have great potential as alternative diets for European seabass, without affecting growth performance, gut homeostasis, or overall fitness. This also highlights the importance of animal proteins in diets of European seabass, as the addition of a small amount of these alternative animal protein sources significantly improved all measured parameters.

Effects of Phytase and Microalgae Supplementation on the Utilization of Aquafeeds for European Seabass (Dicentrarchus labrax) Formulated with a High Inclusion Level of Plant Protein

“…Several authors have reported that lipid peroxidation affects long-chain PUFAs [23,51,52]; however, in the present study, the different dietary treatments had not effect on this parameter, since low levels of lipid oxidation were measured in fish muscle (0.7 mg MDA/kg) in all the experimental groups, values that were within the range of perfect quality fish for human consumption [53]. In addition, skin coloration plays an important role in consumer acceptance of farmed fish, with intense skin coloration usually associated with high-quality products [54]. Skin pigmentation is influenced by a wide variety of factors such as genetic, environmental, physiological, dietary, and others [54,55].…”

“…In addition, skin coloration plays an important role in consumer acceptance of farmed fish, with intense skin coloration usually associated with high-quality products [54]. Skin pigmentation is influenced by a wide variety of factors such as genetic, environmental, physiological, dietary, and others [54,55]. In the present study, significant differences were obtained in the parameter a * in fish fed the 2,000F compared to control, though a general trend to show a greenish skin appeared in all the group fed diets supplemented with phytase and microalgae.…”

Enhancing Rearing of European Seabass (Dicentrarchus labrax) in Aquaponic Systems: Investigating the Effects of Enriched Black Soldier Fly (Hermetia illucens) Prepupae Meal on Fish Welfare and Quality Traits

“…Similarly, up to 45% of HPM can successfully replace FM in diets for European seabass juveniles without impairing growth, feed utilization, and digestibility [ 65 ]. Furthermore, Pleic et al [ 26 ] recently demonstrated that, in diets deprived of FM, the replacement of plant-derived ingredients with defatted HPM, alone or in combination with poultry by-product meal, significantly improved the growth performance and led to positive effects on intestinal digestive/absorptive functions and microbial communities in European seabass subadults.…”

“…Furthermore, HPM is rich in bioactive molecules such as chitin, lauric acid, and antimicrobial peptides, which have been reported to have immunostimulatory and anti-inflammatory effects on fish gut [ 16 ]. Nevertheless, the HPM fatty acid profile does not meet the fish nutritional requirements, lacking in long-chain polyunsaturated fatty acids (PUFA), such as EPA and DHA, which raises serious concerns about the use of full-fat HPM in feed formulations, especially for marine fish species [ 25 , 26 ]. For this reason, several studies have been conducted with defatted HPM in both marine and freshwater fish species [ 27 , 28 , 29 , 30 ].…”

Effects of Dietary Plant Protein Replacement with Insect and Poultry By-Product Meals on the Liver Health and Serum Metabolites of Sea Bream (Sparus aurata) and Sea Bass (Dicentrarchus labrax)

“…On the other hand, only a few research studies have evaluated the partial replacement of plant protein-rich feeds with insect and poultry by-product meals, singly or combined, in low-fish meal diets for sea bream [42,43] and sea bass [44]. These studies mostly investigated the dietary effects on appetite, growth performance, gut health, and fish quality, while fish response in terms of liver health status has received limited attention.…”