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Plant-based diet supplemented with Hermetia Illucens in combination with poultry by-product meal - a step closer to sustainable aquafeeds for European sea bass

Within the ongoing Interreg AdriAquaNet project, new feeds were designed and tested at a laboratory scale on sub-adult European sea bass, aiming to enhance the innovation and sustainability of Adriatic aquaculture. For the present study, three tested diet formulations were selected for a comprehensive analysis of transcriptomic profiles of sub-adult European sea bass intestines after performed feeding trial. Selected formulations included two control diets, one rich in fish-derived ingredients (CF) and one rich in plant-derived ingredients (CV). Test diet (VH10P30) contained the same vegetable: fish lipid ratio as the CV diet, replacing crude proteins from the plant- based sources with 10 % of crude proteins from a commercial defatted Hermetia illucens pupae meal and 30 % of poultry by-product meal. Based on quality, 24 samples of total RNA were selected for cDNA library preparation, comprising 4 biological replicates per feeding treatment of two selected intestinal parts, pyloric caeca, and distal intestine (pyloric caeca and distal intestine were paired as subsamples). Single-end 3'UTR sequencing was performed using NextSeq 500 System. Two analyses were performed for differential expression analysis, comparing the VH10P30 test treatment to CF treatment as positive control, and comparing the VH10P30 test treatment to CV treatment as negative control. In total, 1, 963 (915 up and 1048 down) differentially expressed (DE) genes were found in the distal intestine of European sea bass in the VH10P30 treatment vs. CF treatment. Using CV treatment as the negative control, there were 711 (439 up and 272 down) DE genes in the distal intestine of European sea bass in the VH10P30 treatment. In contrast to the distal intestine, no clear differences were detected between the diet treatments in the pyloric caeca of the experimentally fed European sea bass. Possible explanation for these results could be the occurrence of functional specialization along the intestinal tract of European sea bass (Calduch-Giner et al., 2016). Taking into account growth performance and overall fitness of the European sea bass in the VH10P30 treatment, H. illucens larval meal and poultry by-product meal demonstrated great potential as alternative protein sources for European sea bass aquaculture.

insect meal, black soldier fly, transcriptome, sustainable aquaculture

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