Effect of fishmeal and fish oil replacement by vegetable meals and oils on gut health of European sea bass (Dicentrarchus labrax)

The main objective of this study was to assess the effects of graded levels of replacement of fishmeal (FM) and fish oil (FO) by terrestrial meals (TM) and vegetable oils (VO) on gut health of European sea bass (Dicentrarchus labrax) based on gut morphology, gut-associated immune system (GALT) and gut microbiota composition. Reducing the dietary FM and FO levels down to 10 and 3%, respectively did not affect the growth of European sea bass. Increase in TM and VO markedly affected anterior and posterior gut morphology and fatty acid composition, which mirrored the dietary fatty acid profile. FO replacement by VO increased lipid deposition in anterior gut lamina propria, denoting an effect in lipid metabolism and lipoprotein synthesis. In posterior gut, FM replacements by TM induced an engrossment of the submucosa, an up-regulation of the proinflammatory cytokines IL-1β and TNFα genes, a relatively high mucus production and changes in mucosal microbiota profiles. Finally, supplementation of 0%FM-0%FO diets with LC-PUFA contributed to maintain gut homeostasis in terms of GALT response and microbiota profiles alterations. Statement of relevance FM and FO appropriate dietary levels for European seabass