Aquaculture nutrition is at a cross-road : the usage of finite marine resources is a major sustainability challenge while high dietary inclusion of plant proteins has been associated to detrimental effects on growth , promoting inflammation and intestinal dysbiosis. Feed additives enhancing digestive and metabolic processes are of paramount interest and for this reason this study aims to evaluate the effect of a microencapsulated blend of thymol, vanillin and organic acids (AviPlus®Aqua ) on the Atlantic salmon ( Salmo salar L.) mucosal microbiota.
Three hundred Atlantic salmon parrs (average weight of 5.4 g) were distributed into 6 tanks at SPAROS Lda (Portugal). Two diets were manufactured and one of them was enriched with the test additive. Then they were tested in triplicate as Control and D1500. Fish were fed for 13 weeks and then 3 fish per tank were sampled (n=9 per diet) and DNA extracted from the mucosa using QIAmp® Fast DNA Stool Mini Kit. The DNA was sent to an external laboratory for generation of the raw sequence data through Next-generation Sequencing of DNA molecules. All means are described in table 1 and comparison was performed using Student’s-Newman-Keuls test (p value <0.05) in IBM SPSS Statistics V18 software.
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Results strongly highlight that, in the intestinal mucosa at the genus level, D1500 influenced marked changes on the microbiome profile. F ish fed the treated diet showed the appearance of several genera (Nostocaceae , Acutedesmus , Leuconostoc , Bradyrhizobiaceae , Gammaproteobacteria) affecting biodiversity of the bacterial population . It is particularly interesting the appearance of Leuconostoc , since several species of this genera have been associated to beneficial effects towards intestinal dysbiosis. Moreover, the intestinal mucosa of fish fed treated diet showed a significantly lower relative abundance of Sphingomonas , Enterobacteriaceae and Fusobacteriaceae . An increased relative abundance of both genera Sphingomonas and Enterobacteriaceae have been associated to intestinal inflammatory events.
In conclusion this study proved, according with literature on functional additives, that the addition of the botanical based additive (AviPlus® Aqua) at 1.5 kg/MT (D1500) modulated the adherent microbiota in the mucosa of distal intestine, with several of these changes being associated to a preventive role towards dysbiosis.