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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The effect of fish stocking density and dietary supplementation of vitamin C and micronutrients (Mn, Zn and Se) on the development of systemic granulomatosis in juvenile meagre (Argyrosomus regius)

Systematic granulomatosis is a chronic disease that affects the majority of farmed meagre (A. regius). Nutritional imbalances and overcrowding can increase the risk to suffer oxidative stress, and consequently impact the incidence of granulomatosis. In order to evaluate this, juvenile meagre were fed five isolipidic (16.7 %) and isoproteic (49.6 %) fish meal and fish oil-based feeds prepared by adding different levels of vitamin C, minerals (Mn, Zn, Se) with constant vitamin E and K (300 and 35 mg kg-1, respectively): Diet KEC (100 mg kg-1C), Diet KEC+Mn/Zn/Se (100 mg kg-1C, 40 mg kg-1Mn, 200 mg kg-1Zn, 1.5 mg kg-1Se), Diet KECC (600 mg kg-1C), Diet KECCC (1,200 mg kg-1C), Diet KECCCC (3,200 mg kg-1C). All diets were tested at 3.20 kg m-3, but diets KECC and KECCCC was also tested at 6.20 kg m-3. Growth performance was only affected by stocking density, being lower at high density. Percentage of fish with granulomas was significantly lower in fish fed with the highest dietary vitamin C contents (KECCC and KECCCC) at low density. TBARS content was correlated with the percentage of granulomas in liver (R2=0.9439, y=0.003x-0.1242) denoting the involvement of an imbalance oxidative status in the appearance of granulomas. The present results show that high levels of vitamin C (1,200-3,200 mg kg-1C) and low stock density (3.20 kg m-3) favours the growth of juvenile meagre, reducing the lipid peroxidation indicators and decreasing the incidence of granulomas, which confirms that this pathology is mostly triggered by deficiency of antioxidant nutrients, particularly vitamin C

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

Atlantic salmon were fed diets containing graded levels of EPA + DHA (1·0, 1·3, 1·6 and 3·5 % in the diet) and one diet with 1·3 % of EPA + DHA with reduced total fat content. Fish were reared in sea cages from about 275 g until harvest size (about 5 kg) and were subjected to delousing procedure (about 2·5 kg), with sampling pre-, 1 h and 24 h post-stress. Delousing stress affected plasma cortisol and hepatic mRNA expression of genes involved in oxidative stress and immune response, but with no dietary effects. Increasing EPA þ DHA levels in the diet increased the trace mineral levels in plasma and liver during mechanical delousing stress period and whole body at harvest size. The liver Se, Zn, Fe, Cu, and Mn and plasma Se levels were increased in fish fed a diet high in EPA þ DHA (3·5 %) upon delousing stress. Furthermore, increased dietary EPA þ DHA caused a significant increase in mRNA expression of hepcidin antimicrobial peptide (HAMP), which is concurrent with downregulated transferrin receptor (TFR) expression levels. High dietary EPA + DHA also significantly increased the whole-body Zn, Se, and Mn levels at harvest size fish. Additionally, the plasma and whole-body Zn status increased, respectively, during stress and at harvest size in fish fed reduced-fat diet with less EPA + DHA. As the dietary upper limits of Zn and Se are legally added to the feeds and play important roles in maintaining fish health, knowledge on how the dietary fatty acid composition and lipid level affect body stores of these minerals is crucial for the aquaculture industry

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

Atlantic salmon were fed diets containing graded levels of EPA + DHA (1·0, 1·3, 1·6 and 3·5 % in the diet) and one diet with 1·3 % of EPA + DHA with reduced total fat content. Fish were reared in sea cages from about 275 g until harvest size (about 5 kg) and were subjected to delousing procedure (about 2·5 kg), with sampling pre-, 1 h and 24 h post-stress. Delousing stress affected plasma cortisol and hepatic mRNA expression of genes involved in oxidative stress and immune response, but with no dietary effects. Increasing EPA + DHA levels in the diet increased the trace mineral levels in plasma and liver during mechanical delousing stress period and whole body at harvest size. The liver Se, Zn, Fe, Cu, and Mn and plasma Se levels were increased in fish fed a diet high in EPA + DHA (3·5 %) upon delousing stress. Furthermore, increased dietary EPA + DHA caused a significant increase in mRNA expression of hepcidin antimicrobial peptide (HAMP), which is concurrent with downregulated transferrin receptor (TFR) expression levels. High dietary EPA + DHA also significantly increased the whole-body Zn, Se, and Mn levels at harvest size fish. Additionally, the plasma and whole-body Zn status increased, respectively, during stress and at harvest size in fish fed reduced-fat diet with less EPA + DHA. As the dietary upper limits of Zn and Se are legally added to the feeds and play important roles in maintaining fish health, knowledge on how the dietary fatty acid composition and lipid level affect body stores of these minerals is crucial for the aquaculture industry

Increasing dietary levels of the omega-3 long-chain polyunsaturated fatty acids, EPA and DHA, improves the growth, welfare, robustness, and fillet quality of Atlantic salmon in sea cages

The present study evaluated the effects of increasing the dietary levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Atlantic salmon (Salmo salar) reared in sea cages, in terms of growth performance, welfare, robustness, and overall quality. Fish with an average starting weight of 275 g were fed one of four different diets containing 10, 13, 16, and 35 g/kg of EPA and DHA (designated as 1.0%, 1.3%, 1.6%, and 3.5% EPA and DHA) until they reached approximately 5 kg. The 3.5% EPA and DHA diet showed a significantly beneficial effect on growth performance and fillet quality compared with all other diets, particularly the 1% EPA and DHA diet. Fish fed the diet containing 3.5% EPA and DHA showed 400-600 g higher final weights, improved internal organ health scores and external welfare indicators, better fillet quality in terms of higher visual colour score and lower occurrence of dark spots, and higher EPA and DHA content in tissues at the end of the feeding trial. Moreover, fish fed the 3.5% EPA and DHA diet showed lower mortality during a naturally occurring cardiomyopathy syndrome outbreak, although this did not reach statistical significance. Altogether, our findings emphasise the importance of dietary EPA and DHA to maintain good growth, robustness, welfare, and fillet quality of Atlantic salmon reared in sea cages.acceptedVersio

Increasing dietary levels of the omega-3 long-chain polyunsaturated fatty acids, EPA and DHA, improves the growth, welfare, robustness, and fillet quality of Atlantic salmon in sea cages

The present study evaluated the effects of increasing the dietary levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Atlantic salmon (Salmo salar) reared in sea cages, in terms of growth performance, welfare, robustness, and overall quality. Fish with an average starting weight of 275 g were fed one of four different diets containing 10, 13, 16, and 35 g/kg of EPA and DHA (designated as 1.0%, 1.3%, 1.6%, and 3.5% EPA and DHA) until they reached approximately 5 kg. The 3.5% EPA and DHA diet showed a significantly beneficial effect on growth performance and fillet quality compared with all other diets, particularly the 1% EPA and DHA diet. Fish fed the diet containing 3.5% EPA and DHA showed 400-600 g higher final weights, improved internal organ health scores and external welfare indicators, better fillet quality in terms of higher visual colour score and lower occurrence of dark spots, and higher EPA and DHA content in tissues at the end of the feeding trial. Moreover, fish fed the 3.5% EPA and DHA diet showed lower mortality during a naturally occurring cardiomyopathy syndrome outbreak, although this did not reach statistical significance. Altogether, our findings emphasise the importance of dietary EPA and DHA to maintain good growth, robustness, welfare, and fillet quality of Atlantic salmon reared in sea cages

Increasing dietary levels of the omega-3 long-chain polyunsaturated fatty acids, EPA and DHA, improves the growth, welfare, robustness, and fillet quality of Atlantic salmon in sea cages

The present study evaluated the effects of increasing the dietary levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Atlantic salmon (Salmo salar) reared in sea cages, in terms of growth performance, welfare, robustness, and overall quality. Fish with an average starting weight of 275 g were fed one of four different diets containing 10, 13, 16, and 35 g/kg of EPA and DHA (designated as 1.0%, 1.3%, 1.6%, and 3.5% EPA and DHA) until they reached approximately 5 kg. The 3.5% EPA and DHA diet showed a significantly beneficial effect on growth performance and fillet quality compared with all other diets, particularly the 1% EPA and DHA diet. Fish fed the diet containing 3.5% EPA and DHA showed 400-600 g higher final weights, improved internal organ health scores and external welfare indicators, better fillet quality in terms of higher visual colour score and lower occurrence of dark spots, and higher EPA and DHA content in tissues at the end of the feeding trial. Moreover, fish fed the 3.5% EPA and DHA diet showed lower mortality during a naturally occurring cardiomyopathy syndrome outbreak, although this did not reach statistical significance. Altogether, our findings emphasise the importance of dietary EPA and DHA to maintain good growth, robustness, welfare, and fillet quality of Atlantic salmon reared in sea cages

Increasing dietary levels of the omega-3 long-chain polyunsaturated fatty acids, EPA and DHA, improves the growth, welfare, robustness, and fillet quality of Atlantic salmon in sea cages

The present study evaluated the effects of increasing the dietary levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in Atlantic salmon (Salmo salar) reared in sea cages, in terms of growth performance, welfare, robustness, and overall quality. Fish with an average starting weight of 275 g were fed one of four different diets containing 10, 13, 16, and 35 g/kg of EPA and DHA (designated as 1.0%, 1.3%, 1.6%, and 3.5% EPA and DHA) until they reached approximately 5 kg. The 3.5% EPA and DHA diet showed a significantly beneficial effect on growth performance and fillet quality compared with all other diets, particularly the 1% EPA and DHA diet. Fish fed the diet containing 3.5% EPA and DHA showed 400-600 g higher final weights, improved internal organ health scores and external welfare indicators, better fillet quality in terms of higher visual colour score and lower occurrence of dark spots, and higher EPA and DHA content in tissues at the end of the feeding trial. Moreover, fish fed the 3.5% EPA and DHA diet showed lower mortality during a naturally occurring cardiomyopathy syndrome outbreak, although this did not reach statistical significance. Altogether, our findings emphasise the importance of dietary EPA and DHA to maintain good growth, robustness, welfare, and fillet quality of Atlantic salmon reared in sea cages