Do background levels of the pesticide pirimiphosmethyl in plant-based aquafeeds affect food safety of farmed Atlantic salmon?

The substitution of fish oil and fishmeal with plant-based ingredients in commercial aquafeeds for Atlantic salmon, may introduce novel contaminants that have not previously been associated with farmed fish. The organophosphate pesticide pirimiphos-methyl (PM) is one of the novel contaminants that is most prevalent in commercial salmon feed. In this study, the feed-to-fillet transfer of dietary PM and its main metabolites was investigated in Atlantic salmon fillet. Based on the experimental determined PM and metabolite uptake, metabolisation, and elimination kinetics, a physiologically based toxicokinetic (PBTK) compartmental model was developed. Fish fed PM had a relatively low (~4%) PM retention and two main metabolites (2-DAMP and Desethyl-PM) were identified in liver, muscle, kidney and bile. The absence of more metabolised forms of 2-DAMP and Desethyl-PM in Atlantic salmon indicates different metabolism in cold-water fish compared to previous studies on ruminants. The model was used to simulate the long term (>1.5 years) feed-to-fillet transfer of PM + metabolite in Atlantic salmon under realistic farming conditions including seasonal fluctuations in feed intake, growth, and fat deposition in muscle tissue. The model predictions show that with the constant presence of the highest observed PM concentration in commercial salmon feed, fillet PM+ metabolite levels were approximately 5 nmol kg−1, with highest levels for the metabolite 2-DAMP. No EU maximum residue levels (MRL) for PM and its main metabolites exist in seafood to date, but the predicted levels were lower than the MRL for PM in swine of 32.7 nmol kg−1.publishedVersio

Impact of dietary level and ratio of n-6 and n-3 fatty acids on disease progression and mRNA expression of immune and inflammatory markers in Atlantic salmon (Salmo salar) challenged with Paramoeba perurans

The aim of the study was to investigate the influence of dietary level and ratio of n-6/n-3 fatty acids (FA) on growth, disease progression and expression of immune and inflammatory markers in Atlantic salmon (Salmo salar) following challenge with Paramoeba perurans. Fish (80 g) were fed four different diets with different ratios of n-6/n-3 FA; at 1.3, 2.4 and 6.0 and one diet with ratio of 1.3 combined with a higher level of n-3 FA and n-6 FA. The diet with the n-6/n-3 FA ratio of 6.0 was included to ensure potential n-6 FA effects were revealed, while the three other diets were more commercially relevant n-6/n-3 FA ratios and levels. After a pre-feeding period of 3 months, fish from each diet regime were challenged with a standardized laboratory challenge using a clonal culture of P. perurans at the concentration of 1,000 cells L−1. The subsequent development of the disease was monitored (by gross gill score), and sampling conducted before challenge and at weekly sampling points for 5 weeks post-challenge. Challenge with P. perurans did not have a significant impact on the growth of the fish during the challenge period, but fish given the feed with the highest n-6/n-3 FA ratio had reduced growth compared to the other groups. Total gill score for all surfaces showed a significant increase with time, reaching a maximum at 21 days post-challenge and declined thereafter, irrespective of diet groups. Challenge with P. perurans influenced the mRNA expression of examined genes involved in immune and inflammatory response (TNF-α, iNOS, IL4-13b, GATA-3, IL-1β, p53, COX2 and PGE2-EP4), but diet did not influence the gene expression. In conclusion, an increase in dietary n-6/n-3 FA ratio influenced the growth of Atlantic salmon challenged with P. perurans; however, it did not alter the mRNA expression of immune genes or progression of the disease.publishedVersio

Effects of dietary arachidonic acid on the reproductive physiology of female Atlantic cod (Gadus morhua L.)

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Increasing the dietary n-6/n-3 ratio alters the hepatic eicosanoid production after acute stress in Atlantic salmon (Salmo salar)

Earlier studies have indicated that a high inclusion of n-6 fatty acids (FA) in feeds for Atlantic salmon can affect the stress response. To test this hypothesis, Atlantic salmon (Salmo salar) were fed diets containing varying dietary n-6/n-3 FA ratios and different absolute levels of n-6 and n-3 FAs. The fish were divided into two different stress challenge groups, where one group was exposed to three weekly hypoxia challenges for 4 weeks (repeated stress), while one group was left undisturbed. At the end of the experiment, both groups were exposed to an acute stressor (lowering of water level). Thus, effects of the diets on acute stress, repeated stress and the combined effect of these could be investigated. In general, there were few effects of the repeated stress, while fish in all diet groups responded strongly to the acute stress based on several stress markers. Dietary n-6/n-3 ratio did not affect growth, all fish appeared phenotypically healthy, and all groups were able to mount an acute stress response. However, there was an interaction between diet and repeated stress on cortisol response after acute stress, possibly indicating altered hypothalamic-pituitary adrenal axis reactivity in fish fed high n-6/n-3 FA ratio. Hepatic levels of prostaglandin D2 (PGD2) and leukotriene B4 responded differently to acute stress depending on the dietary n-6/n3 FA ratio, indicating an altered acute stress response. Additionally, increasing the dietary n-6/n-3 FA content led to higher levels of PGD2 and PGE2 as well as higher liver triacylglycerol. In summary, the results suggest that increasing the dietary n-6/n-3 FA ratio in salmon feeds can affect the way they respond to stressors in an aquaculture setting, possibly affecting the fish robustness.publishedVersio

Effects of dietary deoxynivalenol or ochratoxin A on performance and selected health indices in Atlantic salmon (Salmo salar)

Post-smolt Atlantic salmon (Salmo salar) were fed with standard feed added one of five concentrations of either pure deoxynivalenol (DON; 0.5–6 mg/kg) or pure ochratoxin A (OTA; 0.2–2.4 mg/kg), or no added toxins for up to 8 weeks. Performance effects (feed intake, feed efficiency, gain, length and condition factor), various clinical biochemical parameters, packed cell volume and vaccination response against Aeromonas salmonicidae were all inversely correlated with DON dose, whereas relative liver weight increased with DON dose. In fish fed OTA, however, the effects at the doses tested were rather small. We observed no effects of OTA exposure on performance parameters, but some clinical biochemical parameters tended to increase with OTA dose primarily at 3 weeks, and compared with controls OTA exposure caused increased mRNA expression of two immune markers in the spleen. No liver histopathological effects were found from DON or OTA exposure. For DON, we derived a BMDL20 of 0.3 mg/kg feed for reduced total protein in plasma, a BMDL5 of 0.5 mg/kg feed for reduced condition factor, and a NOAEL of 1 mg/kg feed for DON. For OTA, a BMDL or NOAEL could not be derived (>2.4 mg/kg).publishedVersio

Long-term feeding of Atlantic salmon with varying levels of dietary EPA+DHA alters the mineral status, but does not affect the stress responses after mechanical delousing stress

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Five salmon dinners per week were not sufficient to prevent the reduction in serum vitamin D in autumn at 60° north latitude: A randomised trial

Low serum concentrations of several vitamins have been linked to increased risk of diseases including insulin resistance and type 2 diabetes (T2D). Fish is a good source of several vitamins, and the prevalence of T2D is low in populations with high fish intake. The aim of the present study was to investigate the effects of high fish intake on vitamins in serum from adults in autumn in South-Western Norway at 60° north latitude. In this randomised clinical trial, sixty-three healthy participants with overweight/obesity consumed 750 g/week of either cod (n 22) or salmon (n 22) as five weekly dinners or were instructed to continue their normal eating habits but avoid fish intake (Control group, n 19) for 8 weeks. The estimated vitamin D intake was significantly increased in the Salmon group when compared with the Cod group (P = 6·3 × 10−4) and with the Control group (P = 3·5 × 10−6), with no differences between groups for estimated intake of vitamins A, B1, B2, B3, B6, B9, C and E. Serum 25-hydroxyvitamin D3 concentration was decreased in all groups after 8 weeks; however, the reduction in the Salmon group was significantly smaller compared with the Cod group (P = 0·013) and the Control group (P = 0·0060). Cod and salmon intake did not affect serum concentrations of the other measured vitamins. The findings suggest that 750 g/week of salmon was not sufficient to prevent a decrease in serum 25-hydroxyvitamin D3 in autumn in South-Western Norway in adults with overweight/obesity.publishedVersio

Dietary combination of vitamin E, C and K affects growth, antioxidant activity, and the incidence of systemic granulomatosis in meagre (Argyrosomus regius)

Systemic granulomatosis is a growing disease with a high morbidity, which affects to the majority of farmed meagre (Argyrosomus regius). The impossibility of isolating any infectious agents has hypothesized a nutritional origin of the disease. In order to try to elucidate the nutritional origin of granulomas, juvenile meagre were fed for 15 weeks with six diets containing different levels of vitamin E and C and with or without addition of vitamin K: Diet 0 (basal premix, no K, 150 mg kg‐−1 E, 20 mg kg‐−1 C), K (added 23 mg kg‐−1 K), EC (300 mg kg‐−1 E, 70 mg kg‐−1 C), KEC (23 mg kg‐−1 K, 300 mg kg‐−1 E, 70 mg kg‐−1 C), EECC (450 mg kg‐−1 E, 230 mg kg‐−1 C) and KEECC (23 mg kg‐−1 K, 450 mg kg‐−1 E, 230 mg kg‐−1 C). The diet EC significantly increased meagre growth in terms of final weight and length. Fish fed the highest levels of vitamin E and C presented lower percentage of granulomas in liver and heart than fish fed diet 0. The scored severity of granulomatosis in liver and kidney (main affected organs) tended to be lower with dietary increase of vitamin E, C and addition of vitamin K (from 1.83 diet 0 to 1.3 diet KEECC and from 0.91 diet 0 to 0.39 diet KEECC). In liver, the diet KEECC significantly increased catalase expression compared with diet 0. In kidney tnfα expression was significantly up-regulated in fish fed diet EECC and KEECC. In heart, low vitamin E and C levels (300 and 70 mg kg‐−1, respectively) significantly increased superoxide dismutase and glutathione peroxidase expression and high addition increased the expression of tnfα and cox-2 (0 or 23 mg kg‐−1 K, 450 mg kg‐−1 E and 230 mg kg‐−1 C, diet EECC and KEECC). The results show that combination of high dietary content of vitamin K and antioxidant vitamins E and C (23, 450 and 230 mg kg‐−1, respectively) influenced in the incidence of the granulomatosis, which suggests that this pathology could be mediated by nutritional factors

Effects of high intake of cod or salmon on gut microbiota profile, faecal output and serum concentrations of lipids and bile acids in overweight adults: a randomised clinical trial

Purpose To explore whether high intake of cod or salmon would affect gut microbiota profile, faecal output and serum concentrations of lipids and bile acids. Methods Seventy-six adults with overweight/obesity with no reported gastrointestinal disease were randomly assigned to consume 750 g/week of either cod or salmon, or to avoid fish intake (Control group) for 8 weeks. Fifteen participants from each group were randomly selected for 72 h faeces collection at baseline and end point for gut microbiota profile analyses using 54 bacterial DNA probes. Food intake was registered, and fasting serum and morning urine were collected at baseline and end point. Results Sixty-five participants were included in serum and urine analyses, and gut microbiota profile was analysed for 33 participants. Principal component analysis of gut microbiota showed an almost complete separation of the Salmon group from the Control group, with lower counts for bacteria in the Bacteroidetes phylum and the Clostridiales order of the Firmicutes phyla, and higher counts for bacteria in the Selenomonadales order of the Firmicutes phylum. The Cod group showed greater similarity to the Salmon group than to the Control group. Intake of fibres, proteins, fats and carbohydrates, faecal daily mass and output of fat, cholesterol and total bile acids, and serum concentrations of cholesterol, triacylglycerols, non-esterified fatty acids and total bile acids were not altered in the experimental groups. Conclusion A high intake of cod or salmon fillet modulated gut microbiota but did not affect faecal output or serum concentrations of lipids and total bile acids. Clinical trial registration This trial was registered at clinicaltrials.gov as NCT02350595.publishedVersio