Odd Helge Romarheim

Bacteria Grown on Natural Gas Prevent Soybean Meal-Induced Enteritis in Atlantic Salmon

Dietary inclusion of solvent extracted soybean meal (SBM) is associated with inflammation in the distal intestine of salmonid fish, commonly referred to as SBM-induced enteritis. The enteritis is linked to alcohol soluble components in SBM, but the mechanisms have not been established. Previous studies show that bacterial meal (BM) containing mainly Methylococcus capsulatus grown on natural gas is a suitable protein source for salmonids. The BM is rich in nucleotides, phospholipids, and small peptides that might be beneficial for intestinal homeostasis. In this study, a fish meal (FM)-based control diet (FM diet) and diets with 200 g/kg SBM (SBM diet), 300 g/kg BM (BM diet), and 300 g/kg BM and 200 g/kg SBM (BM-SBM diet) were fed to juvenile Atlantic salmon (Salmo salar) for 80 d. Dietary inclusion of SBM reduced growth (P = 0.007). Inclusion of BM reduced digestibility of protein (P = 0.002) and lipids (P = 0.011) and increased (P < 0.01) the relative weights (g/kg whole body) of total gut, liver, and stomach, and mid and distal intestine. Fish fed the SBM diet developed enteritis, lacked carbonic anhydrase 12 in the brush border of epithelial cells in distal intestine, and had more epithelial cells reacting for proliferating cell nuclear antigen compared with fish fed the other diets. Fish fed the same amount of SBM combined with BM showed no signs of inflammation in the distal intestine. Our results demonstrate that BM grown on natural gas can be used to prevent SBM-induced enteritis in Atlantic salmon.

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal, soybean meal and white flakes

Abstract The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.

Candida utilis and Chlorella vulgaris counteract intestinal inflammation in Atlantic salmon (Salmo salar L.).

Intestinal inflammation, caused by impaired intestinal homeostasis, is a serious condition in both animals and humans. The use of conventional extracted soybean meal (SBM) in diets for Atlantic salmon and several other fish species is known to induce enteropathy in the distal intestine, a condition often referred to as SBM induced enteropathy (SBMIE). In the present study, we investigated the potential of different microbial ingredients to alleviate SBMIE in Atlantic salmon, as a model of feed-induced inflammation. The dietary treatments consisted of a negative control based on fish meal (FM), a positive control based on 20% SBM, and four experimental diets combining 20% SBM with either one of the three yeasts Candida utilis (CU), Kluyveromyces marxianus (KM), Saccharomyces cerevisiae (SC) or the microalgae Chlorella vulgaris (CV). Histopathological examination of the distal intestine showed that all fish fed the SC or SBM diets developed characteristic signs of SBMIE, while those fed the FM, CV or CU diets showed a healthy intestine. Fish fed the KM diet showed intermediate signs of SBMIE. Corroborating results were obtained when measuring the relative length of PCNA positive cells in the crypts of the distal intestine. Gene set enrichment analysis revealed decreased expression of amino acid, fat and drug metabolism pathways as well as increased expression of the pathways for NOD-like receptor signalling and chemokine signalling in both the SC and SBM groups while CV and CU were similar to FM and KM was intermediate. Gene expression of antimicrobial peptides was reduced in the groups showing SBMIE. The characterisation of microbial communities using PCR-DGGE showed a relative increased abundance of Firmicutes bacteria in fish fed the SC or SBM diets. Overall, our results show that both CU and CV were highly effective to counteract SBMIE, while KM had less effect and SC had no functional effects.

Prevention of soya-induced enteritis in Atlantic salmon ( Salmo salar ) by bacteria grown on natural gas is dose dependent and related to epithelial MHC II reactivity and CD8α + intraepithelial lymphocytes

An experiment was carried out to study the preventive effect of bacterial meal (BM) produced from natural gas against plant-induced enteropathy in Atlantic salmon (Salmo salar). Salmon were fed a diet based on fish meal (FM) or seven diets with 200 g/kg solvent-extracted soyabean meal (SBM) to induce enteritis in combination with increasing levels of BM from 0 to 300 g/kg. Salmon fed a SBM-containing diet without BM developed typical SBM-induced enteritis. The enteritis gradually disappeared with increasing inclusion of BM. By morphometry, no significant (P>0.05) differences in the size of stretches stained for proliferating cell nuclear antigen were found with 150 g/kg BM compared with the FM diet. Increasing BM inclusion caused a gradual decline in the number of cluster of differentiation 8 α positive (CD8α+) intraepithelial lymphocytes, and fish fed BM at 200 g/kg or higher revealed no significant difference from the FM diet. Histological sections stained with antibody for MHC class II (MHC II) showed that fish with intestinal inflammation had more MHC II-reactive cells in the lamina propria and submucosa, but less in the epithelium and brush border, compared with fish without inflammation. There were no significant (P>0.05) differences in growth among the diets, but the highest levels of BM slightly reduced protein digestibility and increased the weight of the distal intestine. In conclusion, the prevention of SBM-induced enteritis by BM is dose dependent and related to intestinal levels of MHC II- and CD8α-reactive cells.

The Noncommensal Bacterium Methylococcus capsulatus (Bath) Ameliorates Dextran Sulfate (Sodium Salt)-Induced Ulcerative Colitis by Influencing Mechanisms Essential for Maintenance of the Colonic Barrier Function

ABSTRACT Dietary inclusion of a bacterial meal has recently been shown to efficiently abolish soybean meal-induced enteritis in Atlantic salmon. The objective of this study was to investigate whether inclusion of this bacterial meal in the diet could abrogate disease development in a murine model of epithelial injury and colitis and thus possibly have therapeutic potential in human inflammatory bowel disease. C57BL/6N mice were fed ad libitum a control diet or an experimental diet containing 254 g/kg of body weight BioProtein, a bacterial meal consisting of Methylococcus capsulatus (Bath), together with the heterogenic bacteria Ralstonia sp., Brevibacillus agri, and Aneurinibacillus sp. At day 8, colitis was induced by 3.5% dextran sulfate sodium (DSS) ad libitum in the drinking water for 6 days. Symptoms of DSS treatment were less profound after prophylactic treatment with the diet containing the BioProtein. Colitis-associated parameters such as reduced body weight, colon shortening, and epithelial damage also showed significant improvement. Levels of acute-phase reactants, proteins whose plasma concentrations increase in response to inflammation, and neutrophil infiltration were reduced. On the other, increased epithelial cell proliferation and enhanced mucin 2 (Muc2) transcription indicated improved integrity of the colonic epithelial layer. BioProtein mainly consists of Methylococcus capsulatus (Bath) (88%). The results that we obtained when using a bacterial meal consisting of M. capsulatus (Bath) were similar to those obtained when using BioProtein in the DSS model. Our results show that a bacterial meal of the noncommensal bacterium M. capsulatus (Bath) has the potential to attenuate DSS-induced colitis in mice by enhancing colonic barrier function, as judged by increased epithelial proliferation and increased Muc2 transcription.

Requirements of n-3 very long-chain PUFA in Atlantic salmon (Salmo salar L): effects of different dietary levels of EPA and DHA on fish performance and tissue composition and integrity.

Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA in the 1990s to the current 70 % plant-based diets with low levels of these fatty acids (FA). The aim of this study was to establish the impacts of low dietary EPA and DHA levels on performance and tissue integrity of Atlantic salmon (Salmo salar). Atlantic salmon (50 g) in seawater were fed fourteen experimental diets, containing five levels (0, 0·5, 1·0, 1·5 and 2·0 %) of EPA, DHA or a 1:1 EPA+DHA plus control close to a commercial diet, to a final weight of 400 g. Lack of EPA and DHA did not influence mortality, but the n-3-deficient group exhibited moderately slower growth than those fed levels above 0·5 %. The heart and brain conserved EPA and DHA levels better than skeletal muscle, liver, skin and intestine. Decreased EPA and DHA favoured deposition of pro-inflammatory 20 : 4n-6 and 20 : 3n-6 FA in membrane phospholipids in all tissues. When DHA was excluded from diets, 18 : 3n-3 and EPA were to a large extent converted to DHA. Liver, skeletal and cardiac muscle morphology was normal in all groups, with the exception of cytoplasm packed with large or foamy vacuoles and sometimes swollen enterocytes of intestine in both deficient and EPA groups. DHA supplementation supported normal intestinal structure, and 2·0 % EPA+DHA alleviated deficiency symptoms. Thus, EPA and DHA dietary requirements cannot be based exclusively on growth; tissue integrity and fish health also need to be considered.