Abstract
Simple SummaryIn a world dramatically harassed by climate changes and overexploitation of resources, the aquaculture expansion poses several challenges. Among the others, aquafeed formulations need to be rethought in a circular economy vision, avoiding food-feed competition, and possibly valorizing one or more ingredients for their functionality. In this context, the present trial showed that Hermetia illucens prepupae, poultry-by products, and red swamp crayfish meals can effectively replace a substantial proportion of vegetable proteins in the diet for gilthead seabream (Sparus aurata) without impairing fish growth and fillet quality. On the contrary, a blend of Tisochrysis lutea and Tetraselmis suecica negatively impacted fish growth and further studies are thus necessary to better valorize their natural content in pigments in fish farming.By answering the need for increasing sustainability in aquaculture, the present study aimed to compare growth, gene expression involved in appetite regulation, physical characteristics, and chemical composition of Sparus aurata fed alternative protein sources. Fish were fed ten iso-proteic, iso-lipidic, and isoenergetic diets: a vegetable-based (CV) and a marine ingredient-rich (CF) diet were set as control diets. The others were prepared by replacing graded levels (10, 20 or 40%) of the vegetable proteins in the CV with proteins from a commercial defatted Hermetia illucens pupae meal (H), poultry by-product meal (PBM) singly (H10, H20, H40, P20, P40) or in combination (H10P30), red swamp crayfish meal (RC10) and from a blend (2:1, w:w) of Tisochrysis lutea and Tetraselmis suecica (MA10) dried biomasses. The increase in ghre gene expression observed in MA10 fed fish matched with increased feed intake and increased feed conversion ratio. Besides, the MA10 diet conferred a lighter aspect to the fish skin (p < 0.05) than the others. Overall, no detrimental effects of H, PBM, and RC meal included in the diets were observed, and fish fatty acid profile resulted as comparable among these groups and CV, thus demonstrating the possibility to introduce H, PBM, and RC in partial replacement of vegetable proteins in the diet for Sparus aurata.
Highlights
To date, aquaculture is the fastest growing farming sector in the world, answering the demand for safe and healthy food for a world population that will reach nearly 10 billion people by 2050 [1]
The remaining diets were prepared replacing graded levels (10, 20 or 40%) of crude protein from the mixture of vegetable protein sources of the CV diet by crude protein from a commercial defatted Hermetia illucens pupae meal (H10, H20, H40), poultry by-product meal (P20, P40) singly or in combination (H10P30, plant proteins were replaced by 10% protein from H meals and 30% protein from PBM), red swamp crayfish meal (RC10) and from a blend (2:1 w:w) of the dried biomass of two marine microalgae (MA-Tisochrysis lutea and Tetraselmis suecica, MA10), respectively, while maintaining the same 67:33 vegetable to fish lipid ratio as in the CV diet
Fish fed diet MA10 resulted in the highest feed intake and in the worst growth performance when compared to both control diets and the other dietary treatments (p < 0.05)
Summary
Aquaculture is the fastest growing farming sector in the world, answering the demand for safe and healthy food for a world population that will reach nearly 10 billion people by 2050 [1]. 39% of the total calculated aquaculture emissions derives from crop feed materials, and another 18% from fishmeal production, feed manufacturing and transport In this regard, a challenge could be to turn this sector in a virtuous cycle, possibly using more sustainable and bioactive ingredients rather than conventional fish and soybean meals. It is widely established that the use of insects as a protein source has a number of advantages (high feed conversion efficiency, reduced land space and water consumption for their production), the most notable being the environmental benefits brought by the possibility to farm insects on bio-waste [3]. Evidence on rainbow trout showed that moderate to high dietary levels of defatted H or PBM, replacing or complementing vegetable protein-rich ingredients in diets completely deprived of fish meal (FM), resulted in improved fish growth and gut health [6]
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