Lesions of the biliary system in Atlantic salmon (Salmo salar L.)

Gallbladders with mucosal outpouchings (diverticula) were found in a population of Atlantic salmon farmed in sea water. Soft tissue calcification affected the skin, skeletal muscle and gut, as identified by histological observations. In addition, inflammation of muscle and intestinal tissue and lymphocytic and fibrous reaction were present in the liver. The general fish population was characterized by poor growth and unspecified mortalities. Here we describe the observed lesions and discuss them in the light of the general health status of the population.Lesions of the biliary system in Atlantic salmon (Salmo salar L.)publishedVersio

Effects of functional ingredients on gut inflammation in Atlantic salmon (Salmo salar L)

publishedVersio

Soya saponins and prebiotics alter intestinal functions in Ballan wrasse (Labrus bergylta)

A 5-week feeding trial was conducted in the cleaner fish Ballan wrasse (Labrus bergylta) for a better understanding of the basic biology of the intestinal functions and health in this stomach less species. During the trial, Ballan wrasse was fed either a reference diet, the reference diet supplemented with (i) a commercial prebiotic (Aquate™ SG, 0·4 %) expected to have beneficial effects, (ii) soya saponins (0·7 %) expected to induce inflammation or (iii) a combination of the prebiotics and the soya saponins to find a remedy for gut inflammation. Blood, intestinal tissue and gut content from four consecutive intestinal segments (IN1 – IN4) were collected. No significant differences in fish growth were observed between the four dietary groups. Saponin supplementation, both alone and in combination with prebiotics, increased weight index of IN2 and IN3 and decreased blood plasma glucose, cholesterol and total protein. Dry matter of intestinal content and activity of digestive enzymes were not affected by diet. Histomorphological analyses revealed a progressing inflammation with increased infiltration by immune cells particularly into the distal parts of the intestine in fish fed diets with saponins, both alone and in combination with prebiotics. Gene expression profiles obtained by RNA sequencing and quantitative PCR mirrored the histological and biochemical changes induced by the saponin load. The study demonstrated that Ballan wrasse gut health and digestive function may be markedly affected by feed ingredients containing antinutrients.publishedVersio

A Screening Study on Effects Varying Dietary Macronutrient Composition on Gut Functions in Lumpfish (Cyclopterus lumpus)

publishedVersio

Technical feed quality influences health, digestion patterns, body mineralization and bone development in farming of the stomachless cleaner fish ballan wrasse (Labrus bergylta)

Farmed ballan wrasse (Labrus bergylta) is an efficient cleaner fish used for non-medicinal delicing of Atlantic salmon in sea cages replacing to an increasing degree wild wrasse due to considerations for biodiversity and risk of overfishing local wrasse populations. Farming of ballan wrasse has been hampered by low growth rates, high prevalence of skeletal deformities and other welfare related pathologies. In this study we investigated how diets identical in composition but differing in their technical characteristics, by being prepared using different feed production technologies, affect fish performance, mineralization, bone development and gut health of the ballan wrasse larvae and juveniles. The different production technologies include the commonly used ‘high temperature’ extrusion, cold extrusion, and agglomeration, resulting in feed pellets with distinctive physicochemical properties. The results revealed that prolonged feeding periods with extruded pellets during ballan wrasse larvae weaning result in low body mineralization and the development of severe skeletal deformities. In juvenile ballan wrasse, the extruded pellet treatment resulted in higher mortality rates, fish with larger livers, indication for increased serum TAG and cholesterol in a similar manner, and increased activity of the digestive enzymes LAP and maltase, most probably as a compensatory mechanism to the assumed reduced availability of protein and carbohydrates of extruded pellets for this fish species. Smaller dietary effects were identified in terms of intestinal morphology and gene transcription rates.publishedVersio

A meta-analysis to determine factors associated with the severity of enteritis in Atlantic salmon (Salmo salar) fed soybean meal-based diets

A meta-analytic approach was used to determine factors associated with the severity of enteritis in distal intestine of Atlantic salmon fed soybean meal (SBM)-based diets. Dataset from 26 fish studies were extracted and standardized for use in the meta-analysis. After standardization, the data were analyzed with ordinal logistic regression model by comparing the SBM treatment(s) in each study with the neutral-reference treatment. The log-odds ratio of the proportional odds model and its standard error were extracted and analyzed using the random effects model to estimate the effect size of dietary SBM on enteritis using four semi-quantitative histological variables: reduction in mucosal fold height; disappearance of supranuclear vacuolization; inflammatory cell infiltration of lamina propria, and of submucosa. Both univariate and multivariate meta-regression were used to identify study factors with significant association to the severity of enteritis in Atlantic salmon. The results showed that fish production phase, feed type, SBM inclusion level, year of study and water temperature are significantly associated with the severity of enteritis in Atlantic salmon. Further meta-analysis of sub datasets according to production phase, revealed that fish reared in seawater were more prone to develop enteritis compared with fish reared in freshwater. The absence of positive relationship between SBM inclusion level and the severity of enteritis was probably due to difference in source, batch, processing, and level of anti-nutritional factors in the SBM used in the different studies combined in the meta-analysis. Subgroup analysis based on year of study revealed that the severity of enteritis in fish fed SBM-based diets has decreased over the years. Additional results revealed that fish fed SBM-based diet at low water temperature showed increased severity of enteritis, compared with fish raised in high water temperature. Linear and quadratic regressions conducted to explore possible impact of enteritis on fish performance, showed that the specific growth rate and thermal growth coefficient of fish decreased with increased severity of enteritis. However, this relationship depends on the fish production phase and the histological variables used for the regression analysis. The current study concluded that the severity of enteritis in Atlantic salmon fed SBM-based diets are significantly associated with fish production phase, feed type, SBM inclusion level, year of study and water temperature, but not the exposure time. Also, the study showed that increased severity of enteritis reduced specific growth rate and thermal growth coefficient of fish fed SBM-based diets.A meta-analysis to determine factors associated with the severity of enteritis in Atlantic salmon (Salmo salar) fed soybean meal-based dietspublishedVersio

Immunization with lytic polysaccharide monooxygenase CbpD induces protective immunity against Pseudomonas aeruginosa pneumonia

publishedVersio

Protein value and health aspects of the seaweeds Saccharina latissima and Palmaria palmata evaluated with mink as model for monogastric animals

The aim of the present work was to evaluate the protein value of products from the two seaweeds Saccharina latissima and Palmaria palmata grown in Norwegian waters and to characterize possible beneficial or detrimental effects in the intestine and other organs. Mink, a well-established model for comparison of nutrient digestibility in monogastric animals was used. Two products from each of the seaweeds, a dried whole biomass and a protein concentrate, were evaluated. Five diets were made; a reference diet based on fish meal, and one for each of the four seaweed products. In the latter four, seaweed supplied 200 g/kg of crude protein. Each diet was fed to four male mink for two weeks. The results showed that diets with seaweed were less palatable than the fish meal diet. The animals fed the whole Saccharina diet had a significantly higher water intake and urine production than the other animals, supposedly due to the very high ash content of this seaweed product. This diet also stood out regarding urine concentration of iodine, which was 300 times higher than for the fishmeal-based diet. Apparent digestibility coefficient (ADC) for total amino acids, estimated by difference, showed low values for all the seaweed products; 0.574 and 0.734 for the whole and protein concentrated Saccharina products, and 0.588 and 0.700 for the two Palmaria products, respectively. The apparent amino acid digestibility coefficients (ADC) showed greater variation and were particularly low for histidine, <0.000 and 0.271 for the whole Saccharina and Palmaria products, respectively. Also, the ADC of methionine was low for these products, and cysteine ADC showed negative values for both Saccharina products. The estimated chemical score of the proteins, based on the digestible amino acids profile, was 0 and 520 g/kg for the whole product and protein concentrate of Saccharina, 260 and 520 g/kg for the whole product and the protein concentrate of Palmaria palmata, respectively. Expression of genes associated with digestive and immune functions showed minor effects in the jejunum, somewhat more pronounced effects in the colon. The latter effects were related to immune functions and lipid metabolism. No diet-related alterations in the histology of the jejunum and colon were observed. The histological investigation of liver and kidney structure showed some alterations in the seaweed fed animals. Regarding microbiota assemblage in mucosa of jejunum and colon, no clear diet effects were observed either in richness or diversity. In conclusion: the biological value of the seaweed proteins was low. Only one of the products, the Palmaria protein concentrate, might be considered of any use as a protein source. No clear beneficial or detrimental effects of the seaweed products were observed on gut health and function. The results regarding kidney structure and function, as well as the high iodine in the urine, indicating that further investigations are required to secure that animal health is not challenged by use of these seaweed ingredients in animal diets.publishedVersio

Protein value and health aspects of the seaweeds Saccharina latissima and Palmaria palmata evaluated with mink as model for monogastric animals

The aim of the present work was to evaluate the protein value of products from the two seaweeds Saccharina latissima and Palmaria palmata grown in Norwegian waters and to characterize possible beneficial or detrimental effects in the intestine and other organs. Mink, a well-established model for comparison of nutrient digestibility in monogastric animals was used. Two products from each of the seaweeds, a dried whole biomass and a protein concentrate, were evaluated. Five diets were made; a reference diet based on fish meal, and one for each of the four seaweed products. In the latter four, seaweed supplied 200 g/kg of crude protein. Each diet was fed to four male mink for two weeks. The results showed that diets with seaweed were less palatable than the fish meal diet. The animals fed the whole Saccharina diet had a significantly higher water intake and urine production than the other animals, supposedly due to the very high ash content of this seaweed product. This diet also stood out regarding urine concentration of iodine, which was 300 times higher than for the fishmeal-based diet. Apparent digestibility coefficient (ADC) for total amino acids, estimated by difference, showed low values for all the seaweed products; 0.574 and 0.734 for the whole and protein concentrated Saccharina products, and 0.588 and 0.700 for the two Palmaria products, respectively. The apparent amino acid digestibility coefficients (ADC) showed greater variation and were particularly low for histidine, <0.000 and 0.271 for the whole Saccharina and Palmaria products, respectively. Also, the ADC of methionine was low for these products, and cysteine ADC showed negative values for both Saccharina products. The estimated chemical score of the proteins, based on the digestible amino acids profile, was 0 and 520 g/kg for the whole product and protein concentrate of Saccharina, 260 and 520 g/kg for the whole product and the protein concentrate of Palmaria palmata, respectively. Expression of genes associated with digestive and immune functions showed minor effects in the jejunum, somewhat more pronounced effects in the colon. The latter effects were related to immune functions and lipid metabolism. No diet-related alterations in the histology of the jejunum and colon were observed. The histological investigation of liver and kidney structure showed some alterations in the seaweed fed animals. Regarding microbiota assemblage in mucosa of jejunum and colon, no clear diet effects were observed either in richness or diversity. In conclusion: the biological value of the seaweed proteins was low. Only one of the products, the Palmaria protein concentrate, might be considered of any use as a protein source. No clear beneficial or detrimental effects of the seaweed products were observed on gut health and function. The results regarding kidney structure and function, as well as the high iodine in the urine, indicating that further investigations are required to secure that animal health is not challenged by use of these seaweed ingredients in animal diets

Effects of dietary lipid level on growth, digestive physiology and disease resistance in lumpfish (Cyclopterus lumpus)

Lumpfish (Cyclopterus lumpus) aquaculture has expanded greatly in recent years due to demands for sea lice cleanerfish from the salmon industry. There are knowledge gaps in lumpfish digestive physiology, nutrient requirement and implications of nutrition for health and disease susceptibility. The present study, conducted to follow up our recent screening trials for estimation of optimal balance of protein, lipid and carbohydrate in diets for lumpfish, involved challenging the fish with Aeromonas salmonicida after a feeding period with diets varying in lipid composition. Three experimental diets were formulated to have similar content of digestible protein and carbohydrate but varying in content of lipid from 6.7 to 18%. Lumpfish with average body weight at start of 1.7 ± 0.03 g were fed the experimental diets in triplicate tanks each (110 fish per tank, in total 990 fish in 9 tanks) for a period of 90 days. After termination of the feeding trial and subsequent collection of biological samples, remaining fish were challenged with atypical A. salmonicida. No significant effects of diet were observed for growth performance. Carcass composition showed increasing content of lipid, protein, and energy with increasing dietary lipid level. Increasing dietary lipid also increased hepatic dry matter, lipid and energy levels, while crude protein decreased. Blood plasma nutrient levels and biomarkers of liver function showed few significant effects of diet, but dietary lipid level increased plasma cholesterol. Intestinal trypsin activity increased with increasing dietary lipid, whereas activity of other digestive enzymes and digesta bile salt levels were unaffected by diet. Increasing lipid level also increased lipid accumulation in the proximal and mid intestine. Expression profiling of genes related to digestive and immune function showed few effects of diet, but the nutrient transporters fabp2 and slc15a1, as well as the immune genes MHCII, igm, and nfkb showed increases with dietary lipid levels, whereas the cholesterol transporter npc1l1 was suppressed. Diet composition did not affect the lumpfish’ resistance against A. salmonicida. To conclude, the variation in macronutrient composition induced modulations in metabolic, digestive and some immune functions. Modulations seemed however to be within normal ranges and did not produce clear compromises in immune responses to bacterial infection.Effects of dietary lipid level on growth, digestive physiology and disease resistance in lumpfish (Cyclopterus lumpus)publishedVersio