Effects of dietary soyabean meal, inulin and oxytetracycline on intestinal microbiota and epithelial cell stress, apoptosis and proliferation in the teleost Atlantic salmon (Salmo salar L.)

Abstract

Soyabean meal (SBM)-induced enteritis in the distal intestine of the teleost Atlantic salmon (Salmo salar L.) and other salmonids may be considered a model for diet-related mucosal disorders in other animals and man. The role of the intestinal microbiota in its pathogenesis was explored. Compared to diets containing fishmeal (FM) as the sole protein source, responses to extracted SBM or the prebiotic inulin, with or without oxytetracycline (OTC) inclusion, were studied following a 3-week feeding trial. Intestinal microbiota, organosomatic indices and histology, as well as immunohistochemical detection of proliferating cell nuclear antigen (PCNA), heat shock protein 70 (HSP70) and caspase-3-positive cells in the distal intestine, were studied. Distal intestine somatic indices (DISI) were higher in inulin and lower in SBM compared to FM-fed fish. The low DISI caused by SBM corresponded with histological changes, neither of which was affected by OTC, despite a significant decrease in adherent bacteria count. Image analysis of PCNA-stained sections showed a significant increase in the proliferative compartment length in SBM-fed fish, accompanied by apparent increases in reactivity to HSP70 and caspase-3 along the mucosal folds, indicating induction of cellular repair and apoptosis, respectively. Fish fed the SBM diet had higher total number as well as a more diverse population composition of adherent bacteria in the distal intestine. Thus SBM-induced enteritis is accompanied by induction of distal intestinal epithelial cell protective responses and changes in microbiota. Putative involvement of bacteria in the inflammatory response merits further investigation.

An initial investigation replacing fish meal with a commercial fermented soybean meal product in the diets of juvenile rainbow trout

“…Soybean meal in rainbow trout diets produces welldocumented deleterious effects on the distal intestine, such as morphological changes and subacute enteritis [12][13][14][15][16][17][18][19], as well as changes to intestinal microbial communities [15,16,18], and hepatic morphology [12]. Similar effects have been reported in Atlantic salmon Salmo salar [20][21][22][23].…”

Evaluation of Prebiotic and Probiotic Effects on the Intestinal Gut Microbiota and Histology of Atlantic salmon (Salmo salar L.)

“…To the authors' knowledge there is very little information regarding the effect of prebiotics on carnobacteria within the GI tract of fish. However, some studies suggest that the carnobacteria populations within the GI tract of salmonids are effected by various dietary factors such as krill meal [32] and oxytetracycline [29] in Atlantic salmon and dietary carbohydrates in Arctic charr (Salvelinus alpinus L.) [19,35]. However, it was observed that the presence of dietary inulin (a prebiotic-type carbohydrate) tended to lower culturable autochthonous carnobacteria levels (by ca.…”

“…have often been reported to be components of the gut microbiota of salmonids; indeed, C. maltaromaticum, C. mobile, C. divergens and Carnobacterium spp. have been identified from Atlantic salmon [29][30][31][32][33]. The consistency of isolation of these species indicates that these might be common core components of the GI microbiome of Atlantic salmon and are likely to be of importance to the host.…”

“…and C. divergens were the dominant bacteria isolated. All of these listed bacteria have previously been isolated from the intestine of Atlantic salmon [29,30,34]. The bacterial composition of the PI observed in the prebiotic fed fish exposed to saline (group 5) showed greater bacterial diversity than that observed from control fed fish exposed to saline (groups 1 and 3).…”

“…Psychrobacter, Carnobacterium and Pseudomonas spp. are commonly reported in the GI tract of fish, and these bacteria have previously been isolated and identified from the GI tract of salmonids [3,[25][26][27][28][29][30]. Carnobacterium spp.…”