Abstract
The efficacy of a microbial feed additive (Bactocell®) in countering intestinal inflammation in Atlantic salmon was examined in this study. Fish were fed either the additive-coated feed (probiotic) or feed without it (control). After an initial 3-week feeding, an inflammatory condition was induced by anally intubating all the fish with oxazolone. The fish were offered the feeds for 3 more weeks. Distal intestine from the groups was obtained at 4 h, 24 h, and 3 weeks, after oxazolone treatment. Inflammatory responses were prominent in both groups at 24 h, documented by changes in intestinal micromorphology, expression of inflammation-related genes, and intestinal proteome. The control group was characterized by edema, widening of intestinal villi and lamina propria, infiltration of granulocytes and lymphocytes, and higher expression of genes related to inflammatory responses, mul1b, il1b, tnfa, ifng, compared to the probiotic group or other time points of the control group. Further, the protein expression in the probiotic group at 24 h after inducing inflammation revealed five differentially regulated proteins – Calr, Psma5, Trp1, Ctsb, and Naga. At 3 weeks after intubation, the inflammatory responses subsided in the probiotic group. The findings provide evidence that the microbial additive contributes to intestinal homeostasis in Atlantic salmon.
Highlights
Feed ingredients of plant origin have become integral parts of aquafeeds of even carnivorous fish species such as Atlantic salmon
There were more goblet cells, intraepithelial lymphocytes (IELs), and supranuclear vacuoles (Figure S2 in Supplementary Material) in the villi, and more immune cells were evident in the lamina propria
The onset of inflammation was discernible in the control group at 4 h after the induction of inflammation (Figure 1B; Figure S2 in Supplementary Material), characterized by granulocyte(neutrophil) infiltration into the widened lamina propria
Summary
Feed ingredients of plant origin have become integral parts of aquafeeds of even carnivorous fish species such as Atlantic salmon. Soybean-induced enteritis in farmed fish, which has similarities to intestinal enteropathies in human beings [1], has been acknowledged as a major nutritional pathology. Mammalian studies have demonstrated that exogenous immunomodulatory feed components that are intended to improve gut health aid in overcoming feed-induced enteropathy by preventing the destruction of epithelial cells as well as an increase of para- and trans-cellular permeability [5]. Probiotics can improve the intestinal epithelial barrier function by stimulating and stabilizing the Microbial additive abates intestinal inflammation gut mucosal immunological barrier [6]. They have been found to affect the growth of beneficial microorganisms positively and alleviate ulcerative colitis in human beings [7]. Experimental murine models that were used to study colitis revealed the anti-inflammatory properties and proinflammatory cytokine activity blocking function of probiotics [8]
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