Despite a long history of rearing Atlantic salmon in hatcheries in Norway, knowledge of molecular... more Despite a long history of rearing Atlantic salmon in hatcheries in Norway, knowledge of molecular and physiological aspects of juvenile development is still limited. To facilitate introduction of alternative feed ingredients and feed additives during early phases, increased knowledge regarding the ontogeny of the digestive apparatus in salmon is needed. In this study, we characterized the development of the gastrointestinal tract and accessory digestive organs for five months following hatch by using histological, biochemical and molecular methods. Furthermore, the effects of a diet containing 16.7% soybean meal (SBM) introduced at start-feeding were investigated, as compared to a fishmeal based control diet. Salmon yolk sac alevins and fry were sampled at 18 time points from hatch until 144 days post hatch (dph). Histomorphological development was investigated at 7, 27, 46, 54 and 144 dph. Ontogenetic expression patterns of genes encoding key digestive enzymes, nutrient transporters, gastrointestinal peptide hormones and T-cell markers were analyzed from 13 time points by qPCR. At 7 dph, the digestive system of Atlantic salmon alevins was morphologically distinct with an early stomach, liver, pancreas, anterior and posterior intestine. About one week before the yolk sac was internalized and exogenous feeding was started, gastric glands and developing pyloric caeca were observed, which coincided with an increase in gene expression of gastric and pancreatic enzymes and nutrient transporters. Thus, the observed organs seemed ready to digest external feed well before the yolk sac was absorbed into the abdominal cavity. In contrast to post-smolt Atlantic salmon, inclusion of SBM did not induce intestinal inflammation in the juveniles. This indicates that SBM can be used in compound feeds for salmon fry from start-feeding to at least 144 dph and/or 4-5 g body weight.
Journal of agricultural and food chemistry, Jan 23, 2015
Soybean meal-induced enteritis (SBMIE) is a well-described condition in the distal intestine of s... more Soybean meal-induced enteritis (SBMIE) is a well-described condition in the distal intestine of salmonids, and saponins have been implicated as the causal agent. However, the question remains whether saponins alone cause SBMIE. Moreover, the dose response relationship has not been described. In a 10-week feeding trial with Atlantic salmon, a highly purified (95%) soya saponin preparation was supplemented (0, 2, 4, 6 or 10 g/kg) to two basal diets, one containing fishmeal as the major protein source (FM), and the other 25% lupin meal (LP). Saponins caused dose-dependent increases in the severity of inflammation independent of basal diet, with concomitant alterations in digestive functions and immunological marker expression. Thus saponins induced inflammation whether the diet contained other legume components or not. However, responses were often the same or stronger in fish fed the corresponding saponin-supplemented LP diets despite lower saponin exposure, suggesting potentiation by...
Responses in Atlantic salmon (Salmo salar L.) juveniles (fry) fed diets containing genetically mo... more Responses in Atlantic salmon (Salmo salar L.) juveniles (fry) fed diets containing genetically modified maize (Bt-maize, MON810) expressing Cry1Ab protein from first-feeding were investigated during a 99-day feeding trial. Four experimental diets were made; each diet contained ,20% maize, either Bt-maize or its near-isogenic maternal line (non-GM maize). One pair was fishmeal-based while the other pair included standard (extracted) soybean meal (SBM; 16.7% inclusion level), with the intention of investigating responses to the maize varieties in healthy fish as well as in immunologically challenged fish with SBM-induced distal intestinal inflammation, respectively. Three replicate tanks of fry (0.1760.01 g; initial mean weight 6 SEM) were fed one of the four diets and samples were taken on days 15, 36, 48 and 99. Survival, growth performance, whole body composition, digestive function, morphology of intestine, liver and skeleton, and mRNA expression of some immune and stress response parameters in the distal intestine were evaluated. After 99 days of feeding, survival was enhanced and the intended SBM-induced inflammatory response in the distal intestine of the two groups of SBM-fed fish was absent, indicating that the juvenile salmon were tolerant to SBM. Mortality, growth performance and body composition were similar in fish fed the two maize varieties. The Bt-maize fed fish, however, displayed minor but significantly decreased digestive enzyme activities of leucine aminopeptidase and maltase, as well as decreased concentration of gut bile salts, but significantly increased amylase activity at some sampling points. Histomorphological, radiographic and mRNA expression evaluations did not reveal any biologically relevant effects of Bt-maize in the gastrointestinal tract, liver or skeleton. The results suggest that the Cry1Ab protein or other compositional differences in GM Bt-maize may cause minor alterations in intestinal responses in juvenile salmon, but without affecting overall survival, growth performance, development or health.
The main function of the alimentary tract of any animal is the acquisition of food with subsequen... more The main function of the alimentary tract of any animal is the acquisition of food with subsequent assimiliation of vital nutrients. The natural diet of fishes varies tremendously between fish species and their natural habitats. Likewise, the structure of the digestive tract varies in the vastly ...
Soyabean meal (SBM)-induced enteritis in the distal intestine of the teleost Atlantic salmon (Sal... more 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.
Inclusion of plant protein sources such as soyabean meal (SBM) in aquafeeds is associated with de... more Inclusion of plant protein sources such as soyabean meal (SBM) in aquafeeds is associated with decreased lipid digestibility, reduced bile acid levels and hypocholesterolaemia. The mechanism for these metabolic abnormalities is unknown. The present study aimed at gaining further insight into how cholesterol and bile acid metabolism is modulated by SBM feeding by quantifying a number of mRNA species corresponding to key proteins involved in cholesterol and bile acid metabolism using quantitative real-time PCR. A 21 d feeding trial with sequential sampling at ten time points following initiation of 20% SBM exposure was conducted on Atlantic salmon. A histological evaluation confirmed distal intestinal enteritis after 5 d of dietary exposure to the SBM, whereas diminished glycogen/lipid deposition was the only relevant finding observed in the liver. SBM inclusion resulted in reduced body pools of cholesterol and bile acids. Hepatic gene expression profiles revealed up-regulation of genes encoding rate-limiting enzymes in cholesterol (3-hydroxy-3-methyl-glutaryl-CoA reductase; HMGCR) and bile acid (cytochrome P4507A1 (CYP7A1)) biosynthesis, as well as up-regulation of their associated transcription factors (sterol regulatory element binding proteins 1 and 2, liver X receptor, farnesoid X receptor and PPAR isoforms). Hepatic gene expressions of cholesterol (ATP binding cassette G5 (ABCG5)) and bile acid (ATP binding cassette B11 (ABCB11)) transporters were, by and large, not influenced by the SBM, but distal intestinal expression patterns of ABCG5 and apical Na-dependent bile acid transporter indicated impaired cholesterol and bile acid reabsorption. In conclusion, hepatic gene expression profiles indicated that the capacity for cholesterol and bile acid synthesis was up-regulated, whereas the indicated impaired cholesterol and bile acid reabsorption probably occurred as a direct result of distal intestinal inflammation.
Physiological and health related responses to dietary inclusion of genetically modified (GM) full... more Physiological and health related responses to dietary inclusion of genetically modified (GM) full-fat soybean meal (Roundup Ready Ò ; GM-soy) and maize (MON810 Ò Bt-maize; GM-maize), as well as non-parental, untransformed lines (nGM-soy and nGM-maize D2), were evaluated in farmed Atlantic salmon (Salmo salar L.) parr during the first 8 months of feeding. Significant effects of dietary GM presence were only found in intestinal Na + -dependent D-glucose uptake and SGLT1 protein level in the region pyloric caeca in which the highest values were found in the GM-soy, intermediate in the nGM-soy, and lowest in the standard FM fed groups. Data from this study confirm that GM soybeans (RRS Ò ) and maize (MON810 Ò ) at inclusion levels of about 6% appear to be as safe as commercially available nGM soy and maize in diets for Atlantic salmon parr. Results from studies with higher inclusion levels and with nonmodified, isogenic or near-isogenic parental lines as control groups are pending.
This study was conducted to investigate the longterm effects of feeding plant products from both ... more This study was conducted to investigate the longterm effects of feeding plant products from both traditional breeding and from biotechnology on intestinal somatic indices, histology and cell proliferation in first-feeding Atlantic salmon, Salmo salar L. (initial weight 0.21 AE 0.02 g). A standard fishmeal diet (standard fishmeal) was formulated to contain fishmeal as the sole protein source and suprex maize as the main starch source. Six experimental diets were then developed: two in which some of the fishmeal was replaced with commercially available, genetically modified Roundup Ready Ò full-fat soybean meal (GM-soy) or commercially available, non-GM full-fat soybean meal (nGM-soy) at a level of 12.5% of the total diet, and four diets in which the suprex maize was replaced with two lines of GM-maize (Dekalb 1; D1 and Pioneer 1; P1), both products of event MON810, and their half-sibling non-GM counterparts (Dekalb 2; D2 and Pioneer 2; P2), at a level of 12.1% of total diet. Each diet was fed to fish in triplicate tanks and the experiment lasted for 8 months, during which the fish reached a final weight of 101-116 g. There was no significant effect of diet on the intestinal indices, nor were histological changes observed in the pyloric caeca or mid intestine. In the distal intestine, one of nine sampled fish fed nGM-soy showed moderate changes, two of nine sampled fish fed GM-soy showed changes, one with moderate and one with logical parameters of the Atlantic salmon intestinal tract.
The paper reports the second and final part of an experiment aiming to study physiological and he... more The paper reports the second and final part of an experiment aiming to study physiological and health-related effects of genetically modified (GM) soybean meal (SBM) type Roundup Ready Ò soybean (RRS) in diets for post-smolt Atlantic salmon. For 3 months salmon were fed diets containing 172 g kg )1 full-fat SBM from RRS (GM-soy) or an unmodified, non-isogenic line (nGM-soy), or a reference diet with fishmeal as the sole protein source (FM). Slight differences in anti-nutrient levels were observed between the GM and nGMsoy. Histological changes were observed only in the distal intestine of the soy-fed fish. The incidence of moderate inflammation was higher in the GM-soy group (9 of 10 sampled fish) compared with the nGM-soy group (7 of 10). However, no differences in the concomitant decreases in activities of digestive enzymes located in the brush border (leucine aminopeptidase and maltase) and apical cytoplasm (acid phosphatase) of enterocytes or in the number of major histocompatibility complex class II+ cells, lysozyme activity, or total IgM of the distal intestine were observed. GM compared with nGMsoy fed fish had higher head kidney lysozyme (11 856 vs. 10 456 units g )1 tissue) and a tendency towards higher acid phosphatase (0.45 vs. 0.39 lmol h )1 kg )1 body mass in whole tissue) activities, respectively. Plasma insulin and thyroxin levels, and hepatic fructose-1,6-bisphosphatase and ethoxyresorufin-O-deethylase activities were not significantly affected. It is not possible, however, to conclude whether the differences in responses to GM-soy were due to the genetic modification or to differences in soy cultivars in the soy-containing diets. Results from studies using non-modified, parental line soybeans as the control group are necessary to evaluate whether genetic modification of soybeans in diets poses any risk to farmed Atlantic salmon.
T-cell-mediated hypersensitivity could be central in soybean meal (SBM)-induced intestinal change... more T-cell-mediated hypersensitivity could be central in soybean meal (SBM)-induced intestinal changes in salmon. However, tools for immunohistochemical detection of T cells have been lacking in teleosts, including Atlantic salmon. Application of a specific histochemical protocol allowed demonstration of T-cell-like reactivities in formalin-fixed, paraffinembedded tissues using an antibody reacting to a conserved region of human CD3e (Dako A0452). Characteristic staining was observed in cells of the thymus as well as distal intestine, skin, gills and spleen. These cells were negative for immunoglobulin M (IgM). Intestinal intraepithelial leucocytes were CD3e positive. During the SBM-induced enteropathy, the mixed inflammatory infiltrate in the lamina propria of the distal intestine included many lymphocytes with a T-cell-like reactivity. Real-time polymerase chain reaction revealed significantly increased expression of a complex polypeptide (CD3pp), CD4 and CD8b (P < 0.05) in the distal intestine of SBM-fed fish compared to fish meal-fed reference fish. Increased reactivity for extracellular IgM in the lamina propria and a positive material between the epithelial cells at the tips of the folds was observed, possibly due to leakage of IgM through an abrogated epithelial barrier. In conclusion, a T-cell-like response appears to be involved in this example of a food-sensitive enteropathy.
This review presents an overview of antinutritive factors (ANFs) relevant for ¢sh nutrition. The ... more This review presents an overview of antinutritive factors (ANFs) relevant for ¢sh nutrition. The sources of ANFs and the possibilities of reducing the impact of ANFs are brie£y mentioned. Proteinase inhibitors, lectins, saponins and oligosaccharides are given a more thorough presentation regarding mechanisms of action and the state of knowledge regarding e¡ects on gut function in ¢sh and upper safe dietary levels. Thereafter, selected results from recent works addressing the involvement of T cells and proteinaseactivated receptors in soybean-induced enteritis are summarized. Our conclusions are as follows: we are only beginning to understand e¡ects of ANFs in ¢sh; strengthening of the knowledge base is urgently needed to understand the e¡ects and to ¢nd the means to overcome or modify these e¡ects; interactions between the e¡ects of ANFs appear to be very important; the microbiota may modify the e¡ects of ANFs; not only salmonids are a¡ected; not only soybeans contain ANFs of biological importance in ¢sh; and with increased knowledge, we can develop better diets for optimal nutrition, health and economy in aquaculture.
The present experiment was conducted to study the possible effects of genetically modified (GM), ... more The present experiment was conducted to study the possible effects of genetically modified (GM), full-fat soybean meal (FFSBM) from Round-up Ready Ò soybeans compared to its parental, and closest near-isogenic, non-modified (nGM) soybean variety, added at moderate (150 g kg )1 ) and high (300 g kg )1 ) inclusion levels. The fish showed a high specific growth rate (SGR 1.27-1.52), and nearly doubled their body weight (BW), with final weights varying from 1009 to 1110 g. Increased levels of dietary FFSBM, independent of the soy being GM or not, significantly decreased mean values of SGR, thermal growth rate, condition factor, final BW, liver somatic index, lipid efficiency ratio, apparent digestibility coefficients (ADC) of protein and gross energy, liver lipid content and plasma cholesterol, and significantly increased ADC of starch and muscle fatty acid levels of 18:3n-3, 20:4n-6, 20:5n-3 and total n-3. Increasing dietary GM FFSBM significantly increased feed conversion ratio, and significantly decreased protein efficiency ratio, ADC of lipid and dry matter and plasma triacylglycerol (TAG) levels. Spleen somatic index was significantly larger in fish groups fed GM FFSBM compared to groups fed nGM FFSBM, which might indicate a possible immune response exerted by the GM soybeans. Mean normalized expression of heat shock protein 70 mRNA in distal intestine was significantly up-regulated while normalized expression of catalase in liver was down-regulated, in fish fed FFSBM compared to fish fed FM. In conclusion, substituting moderate to high levels of GM Round-up Ready Ò FFSBM in diets for Atlantic salmon and compared to the closest nearisogenic counterpart available, resulted in many effects independent of the soy being GM or not, but with the notable exceptions of enlarged spleen and lowered plasma TAG.
Although the inclusion of genetically modified (GM) plants in diets fed to fish is a contentious ... more Although the inclusion of genetically modified (GM) plants in diets fed to fish is a contentious issue, there are few empirical data. The present study addressed nutritional value and potential risks of four maize types (two traditional and two GM maize varieties) and two soy types (one traditional and one Roundup Ready Ò soy) included at moderate levels in diets fed to Atlantic salmon parr (initial mean weight ± SD; 0.21 ± 0.02 g) during the first 8 months of feeding (March to October), which included the parr-smolt transformation. The GM-maize varieties [Dekalb 1 (D1) and Pioneer 1 (P1)] were hybrids of traditional maize variants [Dekalb 2 (D2) and Pioneer 2 (P2)] and the GM maize MON810 Ò . Four maize diets, two soy diets and one Standard fishmeal-based diet were formulated and fed to fish in triplicate. The maize diets were formulated with 121 g kg )1 GM maize (P1 and D1) or 121 g kg )1 of the traditional untransformed line (nGM-maize, P2 and D2) and the soy diets were formulated with 125 g kg )1 GM soy or 125 g kg )1 of the traditional untransformed line (nGM-soy), all of equivalent nutrient composition. All diets supported good growth and showed no evidence of diet-related mortality. Based on samplings every 6th week, growth was within the normal range and at conclusion of the study body weight did not differ among any of the treatments (range 101-116 g). Besides minor differences on heptatosomatic index (HSI), plasma triacylglycerol (TAG) values and thermal growth coefficient (TGC), body composition, relative organ weights, plasma nutrient concentrations and enzyme activities did not vary among treatments at any sampling. The present findings indicate that the inclusion of GM plants at the given level in salmonid diets poses little, or no, adverse risk to the health of first feeding Atlantic salmon parr and promote normal growth. The paper presents the production related data of this feeding study. Results regarding structure and function of intestinal segments and intestinal organs are presented in Sanden et al.
A prebiotic is a non-digestible food ingredient that beneficially affects the host by selectively... more A prebiotic is a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or the activity of one or a limited number of bacteria in the colon. Despite the potential benefits to health and performance as noted in various terrestrial animals, the use of prebiotics in the farming of fish and shellfish has been less investigated. The studies of prebiotics in fish and shellfish have investigated the following parameters: effect on growth, feed conversion, gut microbiota, cell damage/morphology, resistance against pathogenic bacteria and innate immune parameters such as alternative complement activity (ACH50), lysozyme activity, natural haemagglutination activity, respiratory burst, superoxide dismutase activity and phagocytic activity. This review discusses the results from these studies and the methods used. If the use of prebiotics leads to health responses becoming more clearly manifested in fish and shellfish, then prebiotics might have the potential to increase the efficiency and sustainability of aquaculture production. However, large gaps of knowledge exist. To fully conclude on the effects of adding prebiotics in fish diets, more research efforts are needed to provide the aquaculture industry, the scientific community, the regulatory bodies and the general public with the necessary information and tools.
A seven-month feeding trial with genetically modified (GM) Roundup Ready® (RRS®) soybeans was con... more A seven-month feeding trial with genetically modified (GM) Roundup Ready® (RRS®) soybeans was conducted on Atlantic salmon (initial weight 40 g) going through the parr–smolt transformation. The maternal near-isogenic soybean line was used as a non-modified control (non-GM), and the two diets were compositionally similar in all analysed nutrients. The performance and health of the fish were assessed by growth, body
Gastrointestinal lipid absorption in Atlantic salmon was studied following force-feeding with a s... more Gastrointestinal lipid absorption in Atlantic salmon was studied following force-feeding with a standard grower diet to which isotope-labelled free fatty acid (FFA) [1-14 C]-decanoic acid ( 14 C-10:0) and triacylglycerol (TAG) [9,10-3 H(N)]-triolein (trioleic acid; 3 H-18:1) were added. Following force-feeding, the 15 fish, with an average weight of 704 g, were kept in five circular tanks, three fish per tank, supplied with seawater (salinity, 32 g l À1 ). At 3, 6, 12, 18 and 48 h, the fish from one tank were killed, and the gastrointestinal (GI) tract was removed and divided into six 0044-8486/$ -see front matter D
This study was conducted to investigate potential differences between genetically modified (GM) R... more This study was conducted to investigate potential differences between genetically modified (GM) Roundup Ready ® soy and its near-isogenic maternal line as feed ingredients for Atlantic salmon, with focus on intestinal changes commonly caused by soybean meal, histomorphology of other organs and stress response. A 7-month feeding trial was conducted with an inclusion level of 25% GM soy in the diet. Samples for histology were collected after 4 months, after 6 months, when a cross-over of the diet groups was conducted, and at the end of the trial of the crossed-over groups. Histomorphology of spleen, head kidney and mid intestine exhibited no differences between the diet groups, while glycogen deposits in liver were decreased in the GM fed fish at the final sampling. Common soybean meal-induced changes of the distal intestine in Atlantic salmon were observed in both diet groups at all sampling points, within levels expected at the current inclusion level of soy in the diets. However, mucosal fold height in the distal intestine was lower in the GM fed group at one of the three sampling points, and mucosal fold fusion was more pronounced in this group overall in the trial. A stress test conducted at the end of the trial gave responses in haematological parameters, plasma nutrients and mRNA transcription of heat shock protein (HSP) 27 in both liver and distal intestine, but responses were similar between the two diet groups, indicating similar ability to handle stress. The cross-over design, implemented to look at reversibility of potential GM-effects, proved to be inadequate as the crossing of diet groups in itself caused responses that would obscure possible minor diet effects. In conclusion, minor differences were observed between the diet groups; however, GM soy did not appear to cause any adverse effects on organ morphology or stress response compared to non-GM soy.
This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiot... more This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiotic) on the capacity for digestive hydrolysis and amino acid absorption by Atlantic salmon, and how a dietary supplement of the broad-spectrum antibiotic oxytetracycline (OTC) modulated these responses. A control diet (FM) was made from fish meal, fish oil and extruded wheat. Two similar diets were made with 250 g soybean meal (SBM) or 75 g inulin kg − 1 . Each diet was made with or without a supplement of 3 g OTC kg − 1 . All six diets contained yttrium oxide for estimation of apparent nutrient absorption. Each diet was fed to two groups of 172 g salmon kept in 1 m 2 tanks with 9°C saltwater for 3 weeks. Intestinal organs were then sampled and weighed. Gastrointestinal tracts (GIT) were sectioned for analyses of brush border alkaline phosphatase (ALP) and leucine aminopeptidase (LAP) activities. Tissue from the distal intestine (DI) was also fixed for histological examination. Digesta from the different sections were freeze dried for estimation of trypsin and amylase activities, and of apparent absorption of amino acids (AA), nitrogen (N), and sulphur (S). About 85% of the trypsin activity, 70% of the amylase activity, 85% of the ALP activity, and 82% of the LAP activity were found in the proximal (PI) and mid (MI) intestine of fish with functional DI, and the absorption of AA, N, and S was quantitatively completed in the MI. Dietary OTC resulted in lower relative liver weight, but apart from increased ALP and LAP activities in DI when feeding OTC in combination with inulin, OTC did not modify the responses to dietary SBM or inulin. Dietary SBM resulted in lower relative liver weight, and induced pathomorphological changes in the DI mucosa, thus lower the ALP and LAP activities in the DI. SBM also stimulated absorption of AA, N, and S in the PI, but at the same time increased the activities of trypsin and amylase in the DI, indicating reduced re-absorption and increased faecal losses of these endogenous enzymes. Dietary inulin did not damage the DI, and stimulated intestinal growth and higher relative mass of the GIT. Inulin without OTC did not affect the hydrolytic and absorptive capacity of the salmon GIT. Crown
The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by... more The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by bioprocessing the SBM (BPSBM) to remove anti-nutritional factors affected hydrolytic capacity, amino acid absorption, intestinal morphology, and microflora along the intestinal tract of Atlantic cod at two life stages. Three fish meal based standard cod diets were formulated to contain no soy (FM control), 25% SBM, or 22% BPSBM. Prior to sampling the diets were fed to duplicate groups of 0.5 kg (1-year old) and 1.7 kg (2-year old) cod for a period of 3 months, and the groups reached 0.9 and 2.5 kg, respectively. Digesta was then sampled from different intestinal sections for analyses of trypsin and amylase activity as well as absorption of amino acids, nitrogen, and sulphur. Gastrointestinal sections were sampled for measurements of relative weight (kg − 1 body weight), and tissues from these sections were sampled for analyses of brush border enzyme (alkaline phosphatase (ALP), leucine aminopeptidase (LAP), and maltase) activity and histological examination. Microflora was sampled from both digesta and the intestinal wall. The SBM diet stimulated relative growth of all gastrointestinal sections except the distal intestine in both age classes. Relative growth of the pyloric intestine was also stimulated by BPSBM. The pyloric caeca and the upper mid intestine were found to be the major sites for enzymatic hydrolysis of protein and starch and for amino acid absorption. Dietary SBM and BPSBM did not alter the activity of trypsin and LAP, but the activity of these enzymes in the proximal intestine was affected by age, being higher in 1-year old than in 2-year old cod. The rate of amino acid, nitrogen, and sulphur absorption along the gastrointestinal tract was not affected by SBM, but was slowed by BPSBM. Dietary SBM or BPSBM did not alter the morphology of the intestinal mucosa in any sections of the cod intestine. The distal-most structure of the intestine, a compartment with inlet and outlet (anus) valves, showed very high microbial colonisation in the mucosal brush border. Inclusion of SBM in the diet changed the intestinal microflora, increasing the population level of transient bacteria in the pyloric and mid intestine, but reducing the population level of adherent bacteria throughout the intestine. To conclude, Atlantic cod appeared to have a robust and flexible digestive system able to adjust to high dietary levels of soy protein meals.
Antinutritional factors (ANFs) can disrupt digestive and other intestinal functions. ANFs in soyb... more Antinutritional factors (ANFs) can disrupt digestive and other intestinal functions. ANFs in soybean meal (SBM) are implicated in proliferative and inflammatory responses in the intestine of various (functionally) monogastric animals, including Atlantic salmon (Salmo salar L.). The goal of the current study was to investigate the effect of ex vivo exposure of mid and distal intestinal tissue of salmon to soybean saponins (SAP), lectin (LEC) and Kunitz' trypsin inhibitor (KTI), singly and in combination, on epithelial function, as assessed by measuring in vitro glucose uptake pathways along a glucose concentration gradient. As solubilization of SAP in the calciumcontaining Ringer's solution was problematic but resolved with the addition of a physiological concentration of bile collected from the gall bladder of salmon, an evaluation of bile effects became an added element. Results indicated that bile increased baseline glucose absorption and possibly transport, and also had a protective effect on the epithelial barrier, at least partially due to taurocholate. Compared to controls, tissues exposed to LEC + bile, KTI + bile and LEC + KTI + bile exhibited increased glucose uptake at the higher glucose concentrations, apparently due to markedly increased tissue permeability. Addition of SAP, however, attenuated the response, possibly by binding bile components. SAP + bile, also in combination with LEC and/or KTI, as well as LEC, KTI and LEC + KTI without bile often reduced transcellular glucose uptake pathways, while maintaining low tissue permeability. SAP + LEC + KTI + bile, LEC and KTI caused the most marked reductions. The distal intestine was more affected, reflecting the restriction of in vivo SBM-induced inflammatory changes to this region.
Despite a long history of rearing Atlantic salmon in hatcheries in Norway, knowledge of molecular... more Despite a long history of rearing Atlantic salmon in hatcheries in Norway, knowledge of molecular and physiological aspects of juvenile development is still limited. To facilitate introduction of alternative feed ingredients and feed additives during early phases, increased knowledge regarding the ontogeny of the digestive apparatus in salmon is needed. In this study, we characterized the development of the gastrointestinal tract and accessory digestive organs for five months following hatch by using histological, biochemical and molecular methods. Furthermore, the effects of a diet containing 16.7% soybean meal (SBM) introduced at start-feeding were investigated, as compared to a fishmeal based control diet. Salmon yolk sac alevins and fry were sampled at 18 time points from hatch until 144 days post hatch (dph). Histomorphological development was investigated at 7, 27, 46, 54 and 144 dph. Ontogenetic expression patterns of genes encoding key digestive enzymes, nutrient transporters, gastrointestinal peptide hormones and T-cell markers were analyzed from 13 time points by qPCR. At 7 dph, the digestive system of Atlantic salmon alevins was morphologically distinct with an early stomach, liver, pancreas, anterior and posterior intestine. About one week before the yolk sac was internalized and exogenous feeding was started, gastric glands and developing pyloric caeca were observed, which coincided with an increase in gene expression of gastric and pancreatic enzymes and nutrient transporters. Thus, the observed organs seemed ready to digest external feed well before the yolk sac was absorbed into the abdominal cavity. In contrast to post-smolt Atlantic salmon, inclusion of SBM did not induce intestinal inflammation in the juveniles. This indicates that SBM can be used in compound feeds for salmon fry from start-feeding to at least 144 dph and/or 4-5 g body weight.
Journal of agricultural and food chemistry, Jan 23, 2015
Soybean meal-induced enteritis (SBMIE) is a well-described condition in the distal intestine of s... more Soybean meal-induced enteritis (SBMIE) is a well-described condition in the distal intestine of salmonids, and saponins have been implicated as the causal agent. However, the question remains whether saponins alone cause SBMIE. Moreover, the dose response relationship has not been described. In a 10-week feeding trial with Atlantic salmon, a highly purified (95%) soya saponin preparation was supplemented (0, 2, 4, 6 or 10 g/kg) to two basal diets, one containing fishmeal as the major protein source (FM), and the other 25% lupin meal (LP). Saponins caused dose-dependent increases in the severity of inflammation independent of basal diet, with concomitant alterations in digestive functions and immunological marker expression. Thus saponins induced inflammation whether the diet contained other legume components or not. However, responses were often the same or stronger in fish fed the corresponding saponin-supplemented LP diets despite lower saponin exposure, suggesting potentiation by...
Responses in Atlantic salmon (Salmo salar L.) juveniles (fry) fed diets containing genetically mo... more Responses in Atlantic salmon (Salmo salar L.) juveniles (fry) fed diets containing genetically modified maize (Bt-maize, MON810) expressing Cry1Ab protein from first-feeding were investigated during a 99-day feeding trial. Four experimental diets were made; each diet contained ,20% maize, either Bt-maize or its near-isogenic maternal line (non-GM maize). One pair was fishmeal-based while the other pair included standard (extracted) soybean meal (SBM; 16.7% inclusion level), with the intention of investigating responses to the maize varieties in healthy fish as well as in immunologically challenged fish with SBM-induced distal intestinal inflammation, respectively. Three replicate tanks of fry (0.1760.01 g; initial mean weight 6 SEM) were fed one of the four diets and samples were taken on days 15, 36, 48 and 99. Survival, growth performance, whole body composition, digestive function, morphology of intestine, liver and skeleton, and mRNA expression of some immune and stress response parameters in the distal intestine were evaluated. After 99 days of feeding, survival was enhanced and the intended SBM-induced inflammatory response in the distal intestine of the two groups of SBM-fed fish was absent, indicating that the juvenile salmon were tolerant to SBM. Mortality, growth performance and body composition were similar in fish fed the two maize varieties. The Bt-maize fed fish, however, displayed minor but significantly decreased digestive enzyme activities of leucine aminopeptidase and maltase, as well as decreased concentration of gut bile salts, but significantly increased amylase activity at some sampling points. Histomorphological, radiographic and mRNA expression evaluations did not reveal any biologically relevant effects of Bt-maize in the gastrointestinal tract, liver or skeleton. The results suggest that the Cry1Ab protein or other compositional differences in GM Bt-maize may cause minor alterations in intestinal responses in juvenile salmon, but without affecting overall survival, growth performance, development or health.
The main function of the alimentary tract of any animal is the acquisition of food with subsequen... more The main function of the alimentary tract of any animal is the acquisition of food with subsequent assimiliation of vital nutrients. The natural diet of fishes varies tremendously between fish species and their natural habitats. Likewise, the structure of the digestive tract varies in the vastly ...
Soyabean meal (SBM)-induced enteritis in the distal intestine of the teleost Atlantic salmon (Sal... more 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.
Inclusion of plant protein sources such as soyabean meal (SBM) in aquafeeds is associated with de... more Inclusion of plant protein sources such as soyabean meal (SBM) in aquafeeds is associated with decreased lipid digestibility, reduced bile acid levels and hypocholesterolaemia. The mechanism for these metabolic abnormalities is unknown. The present study aimed at gaining further insight into how cholesterol and bile acid metabolism is modulated by SBM feeding by quantifying a number of mRNA species corresponding to key proteins involved in cholesterol and bile acid metabolism using quantitative real-time PCR. A 21 d feeding trial with sequential sampling at ten time points following initiation of 20% SBM exposure was conducted on Atlantic salmon. A histological evaluation confirmed distal intestinal enteritis after 5 d of dietary exposure to the SBM, whereas diminished glycogen/lipid deposition was the only relevant finding observed in the liver. SBM inclusion resulted in reduced body pools of cholesterol and bile acids. Hepatic gene expression profiles revealed up-regulation of genes encoding rate-limiting enzymes in cholesterol (3-hydroxy-3-methyl-glutaryl-CoA reductase; HMGCR) and bile acid (cytochrome P4507A1 (CYP7A1)) biosynthesis, as well as up-regulation of their associated transcription factors (sterol regulatory element binding proteins 1 and 2, liver X receptor, farnesoid X receptor and PPAR isoforms). Hepatic gene expressions of cholesterol (ATP binding cassette G5 (ABCG5)) and bile acid (ATP binding cassette B11 (ABCB11)) transporters were, by and large, not influenced by the SBM, but distal intestinal expression patterns of ABCG5 and apical Na-dependent bile acid transporter indicated impaired cholesterol and bile acid reabsorption. In conclusion, hepatic gene expression profiles indicated that the capacity for cholesterol and bile acid synthesis was up-regulated, whereas the indicated impaired cholesterol and bile acid reabsorption probably occurred as a direct result of distal intestinal inflammation.
Physiological and health related responses to dietary inclusion of genetically modified (GM) full... more Physiological and health related responses to dietary inclusion of genetically modified (GM) full-fat soybean meal (Roundup Ready Ò ; GM-soy) and maize (MON810 Ò Bt-maize; GM-maize), as well as non-parental, untransformed lines (nGM-soy and nGM-maize D2), were evaluated in farmed Atlantic salmon (Salmo salar L.) parr during the first 8 months of feeding. Significant effects of dietary GM presence were only found in intestinal Na + -dependent D-glucose uptake and SGLT1 protein level in the region pyloric caeca in which the highest values were found in the GM-soy, intermediate in the nGM-soy, and lowest in the standard FM fed groups. Data from this study confirm that GM soybeans (RRS Ò ) and maize (MON810 Ò ) at inclusion levels of about 6% appear to be as safe as commercially available nGM soy and maize in diets for Atlantic salmon parr. Results from studies with higher inclusion levels and with nonmodified, isogenic or near-isogenic parental lines as control groups are pending.
This study was conducted to investigate the longterm effects of feeding plant products from both ... more This study was conducted to investigate the longterm effects of feeding plant products from both traditional breeding and from biotechnology on intestinal somatic indices, histology and cell proliferation in first-feeding Atlantic salmon, Salmo salar L. (initial weight 0.21 AE 0.02 g). A standard fishmeal diet (standard fishmeal) was formulated to contain fishmeal as the sole protein source and suprex maize as the main starch source. Six experimental diets were then developed: two in which some of the fishmeal was replaced with commercially available, genetically modified Roundup Ready Ò full-fat soybean meal (GM-soy) or commercially available, non-GM full-fat soybean meal (nGM-soy) at a level of 12.5% of the total diet, and four diets in which the suprex maize was replaced with two lines of GM-maize (Dekalb 1; D1 and Pioneer 1; P1), both products of event MON810, and their half-sibling non-GM counterparts (Dekalb 2; D2 and Pioneer 2; P2), at a level of 12.1% of total diet. Each diet was fed to fish in triplicate tanks and the experiment lasted for 8 months, during which the fish reached a final weight of 101-116 g. There was no significant effect of diet on the intestinal indices, nor were histological changes observed in the pyloric caeca or mid intestine. In the distal intestine, one of nine sampled fish fed nGM-soy showed moderate changes, two of nine sampled fish fed GM-soy showed changes, one with moderate and one with logical parameters of the Atlantic salmon intestinal tract.
The paper reports the second and final part of an experiment aiming to study physiological and he... more The paper reports the second and final part of an experiment aiming to study physiological and health-related effects of genetically modified (GM) soybean meal (SBM) type Roundup Ready Ò soybean (RRS) in diets for post-smolt Atlantic salmon. For 3 months salmon were fed diets containing 172 g kg )1 full-fat SBM from RRS (GM-soy) or an unmodified, non-isogenic line (nGM-soy), or a reference diet with fishmeal as the sole protein source (FM). Slight differences in anti-nutrient levels were observed between the GM and nGMsoy. Histological changes were observed only in the distal intestine of the soy-fed fish. The incidence of moderate inflammation was higher in the GM-soy group (9 of 10 sampled fish) compared with the nGM-soy group (7 of 10). However, no differences in the concomitant decreases in activities of digestive enzymes located in the brush border (leucine aminopeptidase and maltase) and apical cytoplasm (acid phosphatase) of enterocytes or in the number of major histocompatibility complex class II+ cells, lysozyme activity, or total IgM of the distal intestine were observed. GM compared with nGMsoy fed fish had higher head kidney lysozyme (11 856 vs. 10 456 units g )1 tissue) and a tendency towards higher acid phosphatase (0.45 vs. 0.39 lmol h )1 kg )1 body mass in whole tissue) activities, respectively. Plasma insulin and thyroxin levels, and hepatic fructose-1,6-bisphosphatase and ethoxyresorufin-O-deethylase activities were not significantly affected. It is not possible, however, to conclude whether the differences in responses to GM-soy were due to the genetic modification or to differences in soy cultivars in the soy-containing diets. Results from studies using non-modified, parental line soybeans as the control group are necessary to evaluate whether genetic modification of soybeans in diets poses any risk to farmed Atlantic salmon.
T-cell-mediated hypersensitivity could be central in soybean meal (SBM)-induced intestinal change... more T-cell-mediated hypersensitivity could be central in soybean meal (SBM)-induced intestinal changes in salmon. However, tools for immunohistochemical detection of T cells have been lacking in teleosts, including Atlantic salmon. Application of a specific histochemical protocol allowed demonstration of T-cell-like reactivities in formalin-fixed, paraffinembedded tissues using an antibody reacting to a conserved region of human CD3e (Dako A0452). Characteristic staining was observed in cells of the thymus as well as distal intestine, skin, gills and spleen. These cells were negative for immunoglobulin M (IgM). Intestinal intraepithelial leucocytes were CD3e positive. During the SBM-induced enteropathy, the mixed inflammatory infiltrate in the lamina propria of the distal intestine included many lymphocytes with a T-cell-like reactivity. Real-time polymerase chain reaction revealed significantly increased expression of a complex polypeptide (CD3pp), CD4 and CD8b (P < 0.05) in the distal intestine of SBM-fed fish compared to fish meal-fed reference fish. Increased reactivity for extracellular IgM in the lamina propria and a positive material between the epithelial cells at the tips of the folds was observed, possibly due to leakage of IgM through an abrogated epithelial barrier. In conclusion, a T-cell-like response appears to be involved in this example of a food-sensitive enteropathy.
This review presents an overview of antinutritive factors (ANFs) relevant for ¢sh nutrition. The ... more This review presents an overview of antinutritive factors (ANFs) relevant for ¢sh nutrition. The sources of ANFs and the possibilities of reducing the impact of ANFs are brie£y mentioned. Proteinase inhibitors, lectins, saponins and oligosaccharides are given a more thorough presentation regarding mechanisms of action and the state of knowledge regarding e¡ects on gut function in ¢sh and upper safe dietary levels. Thereafter, selected results from recent works addressing the involvement of T cells and proteinaseactivated receptors in soybean-induced enteritis are summarized. Our conclusions are as follows: we are only beginning to understand e¡ects of ANFs in ¢sh; strengthening of the knowledge base is urgently needed to understand the e¡ects and to ¢nd the means to overcome or modify these e¡ects; interactions between the e¡ects of ANFs appear to be very important; the microbiota may modify the e¡ects of ANFs; not only salmonids are a¡ected; not only soybeans contain ANFs of biological importance in ¢sh; and with increased knowledge, we can develop better diets for optimal nutrition, health and economy in aquaculture.
The present experiment was conducted to study the possible effects of genetically modified (GM), ... more The present experiment was conducted to study the possible effects of genetically modified (GM), full-fat soybean meal (FFSBM) from Round-up Ready Ò soybeans compared to its parental, and closest near-isogenic, non-modified (nGM) soybean variety, added at moderate (150 g kg )1 ) and high (300 g kg )1 ) inclusion levels. The fish showed a high specific growth rate (SGR 1.27-1.52), and nearly doubled their body weight (BW), with final weights varying from 1009 to 1110 g. Increased levels of dietary FFSBM, independent of the soy being GM or not, significantly decreased mean values of SGR, thermal growth rate, condition factor, final BW, liver somatic index, lipid efficiency ratio, apparent digestibility coefficients (ADC) of protein and gross energy, liver lipid content and plasma cholesterol, and significantly increased ADC of starch and muscle fatty acid levels of 18:3n-3, 20:4n-6, 20:5n-3 and total n-3. Increasing dietary GM FFSBM significantly increased feed conversion ratio, and significantly decreased protein efficiency ratio, ADC of lipid and dry matter and plasma triacylglycerol (TAG) levels. Spleen somatic index was significantly larger in fish groups fed GM FFSBM compared to groups fed nGM FFSBM, which might indicate a possible immune response exerted by the GM soybeans. Mean normalized expression of heat shock protein 70 mRNA in distal intestine was significantly up-regulated while normalized expression of catalase in liver was down-regulated, in fish fed FFSBM compared to fish fed FM. In conclusion, substituting moderate to high levels of GM Round-up Ready Ò FFSBM in diets for Atlantic salmon and compared to the closest nearisogenic counterpart available, resulted in many effects independent of the soy being GM or not, but with the notable exceptions of enlarged spleen and lowered plasma TAG.
Although the inclusion of genetically modified (GM) plants in diets fed to fish is a contentious ... more Although the inclusion of genetically modified (GM) plants in diets fed to fish is a contentious issue, there are few empirical data. The present study addressed nutritional value and potential risks of four maize types (two traditional and two GM maize varieties) and two soy types (one traditional and one Roundup Ready Ò soy) included at moderate levels in diets fed to Atlantic salmon parr (initial mean weight ± SD; 0.21 ± 0.02 g) during the first 8 months of feeding (March to October), which included the parr-smolt transformation. The GM-maize varieties [Dekalb 1 (D1) and Pioneer 1 (P1)] were hybrids of traditional maize variants [Dekalb 2 (D2) and Pioneer 2 (P2)] and the GM maize MON810 Ò . Four maize diets, two soy diets and one Standard fishmeal-based diet were formulated and fed to fish in triplicate. The maize diets were formulated with 121 g kg )1 GM maize (P1 and D1) or 121 g kg )1 of the traditional untransformed line (nGM-maize, P2 and D2) and the soy diets were formulated with 125 g kg )1 GM soy or 125 g kg )1 of the traditional untransformed line (nGM-soy), all of equivalent nutrient composition. All diets supported good growth and showed no evidence of diet-related mortality. Based on samplings every 6th week, growth was within the normal range and at conclusion of the study body weight did not differ among any of the treatments (range 101-116 g). Besides minor differences on heptatosomatic index (HSI), plasma triacylglycerol (TAG) values and thermal growth coefficient (TGC), body composition, relative organ weights, plasma nutrient concentrations and enzyme activities did not vary among treatments at any sampling. The present findings indicate that the inclusion of GM plants at the given level in salmonid diets poses little, or no, adverse risk to the health of first feeding Atlantic salmon parr and promote normal growth. The paper presents the production related data of this feeding study. Results regarding structure and function of intestinal segments and intestinal organs are presented in Sanden et al.
A prebiotic is a non-digestible food ingredient that beneficially affects the host by selectively... more A prebiotic is a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or the activity of one or a limited number of bacteria in the colon. Despite the potential benefits to health and performance as noted in various terrestrial animals, the use of prebiotics in the farming of fish and shellfish has been less investigated. The studies of prebiotics in fish and shellfish have investigated the following parameters: effect on growth, feed conversion, gut microbiota, cell damage/morphology, resistance against pathogenic bacteria and innate immune parameters such as alternative complement activity (ACH50), lysozyme activity, natural haemagglutination activity, respiratory burst, superoxide dismutase activity and phagocytic activity. This review discusses the results from these studies and the methods used. If the use of prebiotics leads to health responses becoming more clearly manifested in fish and shellfish, then prebiotics might have the potential to increase the efficiency and sustainability of aquaculture production. However, large gaps of knowledge exist. To fully conclude on the effects of adding prebiotics in fish diets, more research efforts are needed to provide the aquaculture industry, the scientific community, the regulatory bodies and the general public with the necessary information and tools.
A seven-month feeding trial with genetically modified (GM) Roundup Ready® (RRS®) soybeans was con... more A seven-month feeding trial with genetically modified (GM) Roundup Ready® (RRS®) soybeans was conducted on Atlantic salmon (initial weight 40 g) going through the parr–smolt transformation. The maternal near-isogenic soybean line was used as a non-modified control (non-GM), and the two diets were compositionally similar in all analysed nutrients. The performance and health of the fish were assessed by growth, body
Gastrointestinal lipid absorption in Atlantic salmon was studied following force-feeding with a s... more Gastrointestinal lipid absorption in Atlantic salmon was studied following force-feeding with a standard grower diet to which isotope-labelled free fatty acid (FFA) [1-14 C]-decanoic acid ( 14 C-10:0) and triacylglycerol (TAG) [9,10-3 H(N)]-triolein (trioleic acid; 3 H-18:1) were added. Following force-feeding, the 15 fish, with an average weight of 704 g, were kept in five circular tanks, three fish per tank, supplied with seawater (salinity, 32 g l À1 ). At 3, 6, 12, 18 and 48 h, the fish from one tank were killed, and the gastrointestinal (GI) tract was removed and divided into six 0044-8486/$ -see front matter D
This study was conducted to investigate potential differences between genetically modified (GM) R... more This study was conducted to investigate potential differences between genetically modified (GM) Roundup Ready ® soy and its near-isogenic maternal line as feed ingredients for Atlantic salmon, with focus on intestinal changes commonly caused by soybean meal, histomorphology of other organs and stress response. A 7-month feeding trial was conducted with an inclusion level of 25% GM soy in the diet. Samples for histology were collected after 4 months, after 6 months, when a cross-over of the diet groups was conducted, and at the end of the trial of the crossed-over groups. Histomorphology of spleen, head kidney and mid intestine exhibited no differences between the diet groups, while glycogen deposits in liver were decreased in the GM fed fish at the final sampling. Common soybean meal-induced changes of the distal intestine in Atlantic salmon were observed in both diet groups at all sampling points, within levels expected at the current inclusion level of soy in the diets. However, mucosal fold height in the distal intestine was lower in the GM fed group at one of the three sampling points, and mucosal fold fusion was more pronounced in this group overall in the trial. A stress test conducted at the end of the trial gave responses in haematological parameters, plasma nutrients and mRNA transcription of heat shock protein (HSP) 27 in both liver and distal intestine, but responses were similar between the two diet groups, indicating similar ability to handle stress. The cross-over design, implemented to look at reversibility of potential GM-effects, proved to be inadequate as the crossing of diet groups in itself caused responses that would obscure possible minor diet effects. In conclusion, minor differences were observed between the diet groups; however, GM soy did not appear to cause any adverse effects on organ morphology or stress response compared to non-GM soy.
This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiot... more This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiotic) on the capacity for digestive hydrolysis and amino acid absorption by Atlantic salmon, and how a dietary supplement of the broad-spectrum antibiotic oxytetracycline (OTC) modulated these responses. A control diet (FM) was made from fish meal, fish oil and extruded wheat. Two similar diets were made with 250 g soybean meal (SBM) or 75 g inulin kg − 1 . Each diet was made with or without a supplement of 3 g OTC kg − 1 . All six diets contained yttrium oxide for estimation of apparent nutrient absorption. Each diet was fed to two groups of 172 g salmon kept in 1 m 2 tanks with 9°C saltwater for 3 weeks. Intestinal organs were then sampled and weighed. Gastrointestinal tracts (GIT) were sectioned for analyses of brush border alkaline phosphatase (ALP) and leucine aminopeptidase (LAP) activities. Tissue from the distal intestine (DI) was also fixed for histological examination. Digesta from the different sections were freeze dried for estimation of trypsin and amylase activities, and of apparent absorption of amino acids (AA), nitrogen (N), and sulphur (S). About 85% of the trypsin activity, 70% of the amylase activity, 85% of the ALP activity, and 82% of the LAP activity were found in the proximal (PI) and mid (MI) intestine of fish with functional DI, and the absorption of AA, N, and S was quantitatively completed in the MI. Dietary OTC resulted in lower relative liver weight, but apart from increased ALP and LAP activities in DI when feeding OTC in combination with inulin, OTC did not modify the responses to dietary SBM or inulin. Dietary SBM resulted in lower relative liver weight, and induced pathomorphological changes in the DI mucosa, thus lower the ALP and LAP activities in the DI. SBM also stimulated absorption of AA, N, and S in the PI, but at the same time increased the activities of trypsin and amylase in the DI, indicating reduced re-absorption and increased faecal losses of these endogenous enzymes. Dietary inulin did not damage the DI, and stimulated intestinal growth and higher relative mass of the GIT. Inulin without OTC did not affect the hydrolytic and absorptive capacity of the salmon GIT. Crown
The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by... more The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by bioprocessing the SBM (BPSBM) to remove anti-nutritional factors affected hydrolytic capacity, amino acid absorption, intestinal morphology, and microflora along the intestinal tract of Atlantic cod at two life stages. Three fish meal based standard cod diets were formulated to contain no soy (FM control), 25% SBM, or 22% BPSBM. Prior to sampling the diets were fed to duplicate groups of 0.5 kg (1-year old) and 1.7 kg (2-year old) cod for a period of 3 months, and the groups reached 0.9 and 2.5 kg, respectively. Digesta was then sampled from different intestinal sections for analyses of trypsin and amylase activity as well as absorption of amino acids, nitrogen, and sulphur. Gastrointestinal sections were sampled for measurements of relative weight (kg − 1 body weight), and tissues from these sections were sampled for analyses of brush border enzyme (alkaline phosphatase (ALP), leucine aminopeptidase (LAP), and maltase) activity and histological examination. Microflora was sampled from both digesta and the intestinal wall. The SBM diet stimulated relative growth of all gastrointestinal sections except the distal intestine in both age classes. Relative growth of the pyloric intestine was also stimulated by BPSBM. The pyloric caeca and the upper mid intestine were found to be the major sites for enzymatic hydrolysis of protein and starch and for amino acid absorption. Dietary SBM and BPSBM did not alter the activity of trypsin and LAP, but the activity of these enzymes in the proximal intestine was affected by age, being higher in 1-year old than in 2-year old cod. The rate of amino acid, nitrogen, and sulphur absorption along the gastrointestinal tract was not affected by SBM, but was slowed by BPSBM. Dietary SBM or BPSBM did not alter the morphology of the intestinal mucosa in any sections of the cod intestine. The distal-most structure of the intestine, a compartment with inlet and outlet (anus) valves, showed very high microbial colonisation in the mucosal brush border. Inclusion of SBM in the diet changed the intestinal microflora, increasing the population level of transient bacteria in the pyloric and mid intestine, but reducing the population level of adherent bacteria throughout the intestine. To conclude, Atlantic cod appeared to have a robust and flexible digestive system able to adjust to high dietary levels of soy protein meals.
Antinutritional factors (ANFs) can disrupt digestive and other intestinal functions. ANFs in soyb... more Antinutritional factors (ANFs) can disrupt digestive and other intestinal functions. ANFs in soybean meal (SBM) are implicated in proliferative and inflammatory responses in the intestine of various (functionally) monogastric animals, including Atlantic salmon (Salmo salar L.). The goal of the current study was to investigate the effect of ex vivo exposure of mid and distal intestinal tissue of salmon to soybean saponins (SAP), lectin (LEC) and Kunitz' trypsin inhibitor (KTI), singly and in combination, on epithelial function, as assessed by measuring in vitro glucose uptake pathways along a glucose concentration gradient. As solubilization of SAP in the calciumcontaining Ringer's solution was problematic but resolved with the addition of a physiological concentration of bile collected from the gall bladder of salmon, an evaluation of bile effects became an added element. Results indicated that bile increased baseline glucose absorption and possibly transport, and also had a protective effect on the epithelial barrier, at least partially due to taurocholate. Compared to controls, tissues exposed to LEC + bile, KTI + bile and LEC + KTI + bile exhibited increased glucose uptake at the higher glucose concentrations, apparently due to markedly increased tissue permeability. Addition of SAP, however, attenuated the response, possibly by binding bile components. SAP + bile, also in combination with LEC and/or KTI, as well as LEC, KTI and LEC + KTI without bile often reduced transcellular glucose uptake pathways, while maintaining low tissue permeability. SAP + LEC + KTI + bile, LEC and KTI caused the most marked reductions. The distal intestine was more affected, reflecting the restriction of in vivo SBM-induced inflammatory changes to this region.
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Papers by Anne Bakke