Supplementing the diet with functional ingredients is a key strategy to improve fish performance ... more Supplementing the diet with functional ingredients is a key strategy to improve fish performance and health in aquaculture. The amino acids of the urea and nitric oxide (NO) cycles-arginine, ornithine and citrulline-perform crucial roles in the immune response through the generation of NO and the synthesis of polyamine used for tissue repair. We previously found that citrulline supplementation improves and maintains circulating free arginine levels in rainbow trout more effectively than arginine supplementation. Here, to test whether supplementation of urea cycle amino acids modulates the immune response in rainbow trout (Oncorhynchus mykiss), we supplemented a commercial diet with high levels (2% of total diet) of either arginine, ornithine or citrulline during a 7-week feeding trial, before challenging fish with the bacterium Aeromonas salmonicida. We carried out two separate experiments to investigate fish survival and 24h post-infection to investigate the immediate response of free amino acid levels, and transcriptional changes in genes encoding urea cycle, NO cycle and polyamine synthesis enzymes. There were no differences in percentage fish mortality between diets, however there were numerous highly significant changes in free amino acid levels and gene expression to both dietary supplementation and infection. Out of 26 amino acids detected in blood plasma, 8 were significantly changed by infection and 9 by dietary supplementation of either arginine, ornithine or citrulline. Taurine, glycine and aspartic acid displayed the largest decreases in circulating levels in infected fish, while ornithine and isoleucine were the only amino acids that increased in concentration. We investigated transcriptional responses of the enzymes involved in arginine metabolism in liver and head kidney; transcripts for polyamine synthesis enzymes showed highly significant increases in both tissues across all diets following infection. The paralogous arginase-encoding genes, Arg1a, Arg1b, Arg2a and Arg2b, displayed complex responses across tissues and also due to diet and infection. Overall, these findings improve our understanding of amino acid metabolism following infection and suggests new potential amino acid targets for improving the immune response in salmonids.
Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA i... more Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA in the 1990s to the current 70 % plant-based diets with low levels of these fatty acids (FA). The aim of this study was to establish the impacts of low dietary EPA and DHA levels on performance and tissue integrity of Atlantic salmon (Salmo salar). Atlantic salmon (50 g) in seawater were fed fourteen experimental diets, containing five levels (0, 0•5, 1•0, 1•5 and 2•0 %) of EPA, DHA or a 1:1 EPA + DHA plus control close to a commercial diet, to a final weight of 400 g. Lack of EPA and DHA did not influence mortality, but the n-3-deficient group exhibited moderately slower growth than those fed levels above 0•5 %. The heart and brain conserved EPA and DHA levels better than skeletal muscle, liver, skin and intestine. Decreased EPA and DHA favoured deposition of pro-inflammatory 20 : 4n-6 and 20 : 3n-6 FA in membrane phospholipids in all tissues. When DHA was excluded from diets, 18 : 3n-3 and EPA were to a large extent converted to DHA. Liver, skeletal and cardiac muscle morphology was normal in all groups, with the exception of cytoplasm packed with large or foamy vacuoles and sometimes swollen enterocytes of intestine in both deficient and EPA groups. DHA supplementation supported normal intestinal structure, and 2•0 % EPA + DHA alleviated deficiency symptoms. Thus, EPA and DHA dietary requirements cannot be based exclusively on growth; tissue integrity and fish health also need to be considered.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2020
Functional amino acids (FAA) regulate metabolic pathways directly linked to health, survival, gro... more Functional amino acids (FAA) regulate metabolic pathways directly linked to health, survival, growth and development. Arginine is a FAA with crucial roles in protein deposition and the immune response. In mammals, supplementation of arginine's precursor amino acid, citrulline, is known to increase circulating arginine to levels beyond direct arginine supplementation, however, citrulline supplementation is poorly studied in fish. To address this knowledge gap, we supplemented the diet of rainbow trout with arginine and its precursor amino acids, ornithine and citrulline, at 3 levels (0.5%, 1% and 2% of the total diet) during a 14-week experiment. We sampled fish at 3h and 24h post-feeding to investigate immediate and steady-state effects, respectively. There were no differences in fish growth for any of the diets across a range of indicators. In blood plasma, out of 26 amino acids detected, 11 and 6 displayed significant changes 24h and 3h post-prandial, respectively. Arginine, ornithine and citrulline levels were all significantly increased by the citrulline supplemented diets. In muscle, 8 amino acids were significantly altered by supplemented diets, while there were no significant changes in liver. Arginine was increased by 2% citrulline supplementation in muscle tissue. We also investigated the transcriptional responses of urea cycle, nitric oxide cycle and rate-limiting polyamine synthesis enzymes, related to arginine's metabolism, in liver. At both time points, only 2 enzymes were significantly altered by the supplemented diets, however several significant changes were observed comparing 3h and 24h post-prandial expression levels. Of these, the paralogous polyamine synthesis enzyme encoding genes ODC1 and ODC2 displayed the largest increases in 3h post-prandial fish. These findings demonstrate that endogenous synthesis of arginine is possible from a citrulline supplemented diet and improve our understanding of arginine metabolism in fish.
-Omega-3 fettsyrer er helt sentrale for en rekke biologiske funksjoner i kroppen, som for eksempe... more -Omega-3 fettsyrer er helt sentrale for en rekke biologiske funksjoner i kroppen, som for eksempel cellenes oppbygging, avlesing av arvematerialet og inflammasjons-respons. Det er for øvrig relativt lite kunnskap om hvor lite omega-3 i fôret oppdrettslaksen kan klare seg med uten at det går ut over helse og velferd. Hensikten med dette prosjektet har dermed vært å øke kunnskapen om hvilke konsekvenser lave nivåer av EPA og DHA i fôret til laks, over store deler av livssyklus, vil ha for fiskens sammensetning og helse i seinere livsfaser. Prosjektet bygger på et fiskemateriale fra NFR prosjektet (224913), hvor atlantisk laks ble fôret med et fiskeoljefritt og fiskemelfritt fôr tilsatt ulike nivåer av EPA, DHA eller en kombinasjon av EPA og DHA fra en fiskestørrelse på 40g til 400g. I FHF prosjektet 900957 ble fisken fulgt videre i sjø på henholdsvis 0,2 %, 1 % og 1,7 % EPA og DHA i fôr fram til slaktestørrelse på ca. 3,5 kg. Resultater fra prosjektet tyder på at 1 % EPA og DHA i fôret, et nivå som tidligere var ansett som nedre behovsnivå, er for lavt til at fisken kan opprettholde god helse under krevende miljøbetingelser. Laks fôret på 1 % EPA og DHA eller lavere, døde i betydelig større grad enn laks fôret med 1,7 % av disse fettsyrene i fôret når fisken ble utsatt for gjentatt håndteringsstress som avlusning ved høye vanntemperaturer. Lave nivå av EPA og DHA i fôret førte bl.a. også til redusert nivå av astaxanthin og EPA og DHA nivå i muskel, økt mengde fett i lever og rundt innvoller, manglende virvelmellomrom i ryggrad og histologiske endringer i midttarm. Denne studien har også vist at lave nivåer av omega-3 i fôret har ulik innvirkning på sammensetningen av membranlipidene til ulike vev. Spesielt i skinnet blir DHA i veldig stor grad erstattet av arakidonsyre (20:4n-6) når DHA nivået reduseres. Samme trend ble observert for tarmens fosfolipider, men i mindre grad enn i skinnet. Lever er et av de mest konserverte vevene med tanke på EPA og DHA. For å sikre en robust laks i sjø, som tåler den håndteringen den møter under naturlig variasjoner i oppdrettsbetingelser, så tyder dataene fra prosjektet på at oppdrettslaksen må ha over 1 % marine omega-3 fettsyrer i fôret for å dekke sitt behov.The omega-3 fatty acids EPA and DHA are essential components in salmon diets due to their important biological functions. More knowledge is required about the minimum requirements that secures the health of Atlantic salmon throughout life. The aim of this project was to study the health consequences of using low dietary levels of EPA and DHA over much of the fish’s life cycle. The results shows that 1 % EPA and DHA in the diet of Atlantic salmon, a level previously regarded as the requirement level, is too low to maintain good health under demanding environmental conditions
Atlantic salmon were fed diets containing graded levels of EPA + DHA (1·0, 1·3, 1·6 and 3·5 % in ... more 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 tra...
The present study evaluated the effects of increasing the dietary levels of EPA and DHA in Atlant... more The present study evaluated the effects of increasing the dietary levels of EPA and 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...
Abstract For a rapidly developing aquaculture industry where availability of raw materials for di... more Abstract For a rapidly developing aquaculture industry where availability of raw materials for diet formulation are quickly changing, it is fundamental to define what are the dietary needs and benefits. In farming of Atlantic salmon (Salmo salar), highly unsaturated fatty acids (HUFA) are known to be essential, and a minimum dietary inclusion is needed. The aim of this study has been to map Atlantic salmon (Salmo salar) performance and midgut health towards dietary HUFA under normal and challenging condition. Atlantic salmon post-smolt at 150 g were fed four experimental diets over a feeding period of 10 weeks up to a final weight of 377 g followed by three weeks of unpredictable chronic stress (UCS). The diets varied in their HUFA level, with either 28.7 g/kg DHA (HDHA), 25 g/kg EPA (HEPA), 21.3 g/kg ARA (HARA) or 8.5 g/kg EPA + DHA (LHUFA). After the feeding period all fish had more than doubled their weight and fish fed HARA showed a significant lower specific growth rate compared to all other diets. Diets had little effect on intestinal morphology, barrier and transport function. Intestinal polar lipid composition suggested higher lipid metabolism in fish feed LHUFA and transcriptome analysis confirm upregulated lipid metabolism and downregulated energy turn over. The low dietary HUFA and high n6/n3 ratio had no major effect on Atlantic salmon performance and intestinal health. Comparing transcriptome profiles from HDHA to HEPA, more upregulated pathways are seen in fish fed HEPA, including metabolism and immunity. The fish feed HARA had downregulated turn-over and metabolism compared to fish fed HEPA. The UCS period resulted in zero growth and lower enterocyte height in all diet groups, and the intestinal barrier was reduced in the paracellular permeability to mannitol. Contradictory to previous studies, fish fed HDHA and HEPA responded to UCS with enhanced intestinal resistance. UCS also resulted in impaired intestinal transport by elevated ion flux and epithelial electrochemical gradient in fish fed LHUFA. Transcriptome pathway analysis indicated more cell turn over and lipid metabolism in LHUFA and HDHA. In conclusion, a low HUFA diet with 8.5 g/kg DHA + EPA can sustain growth and intestinal health under controlled condition, but the health is impaired after three weeks of chronic stress. Decreasing the n6/n3 ratio by increasing levels of EPA and DHA strengthens intestinal barrier in response to chronic stress. Increasing the ARA to HUFA ratio may have a negative effect on growth, but not on intestinal health.
The present study aimed to determine the minimum requirements of the essentialn-3 fatty acids EPA... more The present study aimed to determine the minimum requirements of the essentialn-3 fatty acids EPA and DHA in Atlantic salmon (Salmo salar) that can secure their health under challenging conditions in sea cages. Individually tagged Atlantic salmon were fed 2, 10 and 17 g/kg of EPA + DHA from 400 g until slaughter size (about 3·5 kg). The experimental fish reared in sea cages were subjected to the challenging conditions typically experienced under commercial production. Salmon receiving the lowest EPA + DHA levels showed lower growth rates in the earlier life stages, but no significant difference in final weights at slaughter. The fatty acid composition of various tissues and organs had remarkably changed. The decreased EPA + DHA in the different tissue membrane phospholipids were typically replaced by pro-inflammatoryn-6 fatty acids, most markedly in the skin. The EPA + DHA levels were maintained at a higher level in the liver and erythrocytes than in the muscle, intestine and skin. ...
Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA i... more Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA in the 1990s to the current 70 % plant-based diets with low levels of these fatty acids (FA). The aim of this study was to establish the impacts of low dietary EPA and DHA levels on performance and tissue integrity of Atlantic salmon (Salmo salar). Atlantic salmon (50 g) in seawater were fed fourteen experimental diets, containing five levels (0, 0·5, 1·0, 1·5 and 2·0 %) of EPA, DHA or a 1:1 EPA+DHA plus control close to a commercial diet, to a final weight of 400 g. Lack of EPA and DHA did not influence mortality, but the n-3-deficient group exhibited moderately slower growth than those fed levels above 0·5 %. The heart and brain conserved EPA and DHA levels better than skeletal muscle, liver, skin and intestine. Decreased EPA and DHA favoured deposition of pro-inflammatory 20 : 4n-6 and 20 : 3n-6 FA in membrane phospholipids in all tissues. When DHA was excluded from diets, 18 : 3n-3 an...
Comparative Biochemistry and Physiology Part A: Physiology, 1994
Atlantic cod (0.8-2.5 kg) were transferred from 8OC to l°C seawater for 17 days. No fish died. Ex... more Atlantic cod (0.8-2.5 kg) were transferred from 8OC to l°C seawater for 17 days. No fish died. Exposure to l°C water produced no changes in hematocrit, or in plasma concentrations of Cl-or Mg '+ Cold water exposure caused a marked increase in plasma cortisol and. glucose concentrations. Fish in l°C seawater had higher gill Na-K-ATPase activity than fish in 8OC seawater, whereas there were no differences in gill lipid class or fatty acid composition.
Thesis (Ph. D.)--Norwegian University of Science and Technology, Trondheim, 1997. Includes biblio... more Thesis (Ph. D.)--Norwegian University of Science and Technology, Trondheim, 1997. Includes bibliographical references.
Initial levels of white muscle high-energy phosphates, IMP, ATP:IMPratio, adenylate energy charge... more Initial levels of white muscle high-energy phosphates, IMP, ATP:IMPratio, adenylate energy charge and pH were used as indicators of handling stress when Atlantic salmon were slaughtered. Ante-mortem handling included fish that were either anesthetized (baseline), quickly netted and killed by a blow to the head (unstressed) or chased to exhaustion in the holding tank (stressed). During subsequent storage in ice, freshness was evaluated in terms of IMP, HxR, Hx and K-values. HPLC showed initial differences in distribution of metabolites induced by struggling gradually fell during storage. K-values were different only for 2 days post mortem, but the effect of handling stress was discernible as higher mean K-values and different IMP and HxR contents for up to 7 days post mortem.
Oily fish are an important source of health promoting nutrients such as the very long chain marin... more Oily fish are an important source of health promoting nutrients such as the very long chain marine omega-3 (VLC-n3) fatty acids and simultaneously a source of potentially hazardous contaminants. Fish oils that are used in fish feed are the main source for both contaminants and VLC-n3. Decontamination techniques have recently been developed to effectively remove persistent organic contaminants from fish oils. The aim of the present study was to assess the level of potentially hazardous contaminants and the health beneficial fatty acids in Atlantic salmon reared on novel decontaminated feeds. Atlantic salmon were fed for 18 months (an entire seawater production cycle) on diets based on decontaminated or non-treated (control) fish oils until market size ($5 kg). The level of known notorious persistent organic pollutants (POPs, i.e. dioxins, dioxin-like polychlorinated biphenyls (DL-PCBs), non dioxin-like PCBs, poly brominated diphenyl ethers (PBDE), and organochlorine pesticides), as well as fatty acid composition were analysed in fish oils, the two diets, and Atlantic salmon fillet. The oil decontamination process was a two-step procedure using active carbon and short path distillation. The fillet levels of POPs in market size fish were reduced by 68-85% while the concentration of very long chain omega-3 fatty acids was reduced by 4-7%. No differences in biomarkers of dioxin-like component exposures, such as hepatic gene expression of CYP1A or AhR2B, CYP1A protein expression and 7-ethoxyresorufin O-deethylase (EROD) activity, were observed between salmon raised on normal or decontaminated feeds, thus indicating that the difference in POPs levels were of no biological significance to the fish. Atlantic salmon reared on decontaminated feeds had sum polychlorinated dibenzodioxins/furans (PCDD/Fs) and DL-PCB concentrations that were comparable with terrestrial food products such as beef, while the level of marine omega-3 fatty acids remained as high as for commercially farmed Atlantic salmon.
Supplementing the diet with functional ingredients is a key strategy to improve fish performance ... more Supplementing the diet with functional ingredients is a key strategy to improve fish performance and health in aquaculture. The amino acids of the urea and nitric oxide (NO) cycles-arginine, ornithine and citrulline-perform crucial roles in the immune response through the generation of NO and the synthesis of polyamine used for tissue repair. We previously found that citrulline supplementation improves and maintains circulating free arginine levels in rainbow trout more effectively than arginine supplementation. Here, to test whether supplementation of urea cycle amino acids modulates the immune response in rainbow trout (Oncorhynchus mykiss), we supplemented a commercial diet with high levels (2% of total diet) of either arginine, ornithine or citrulline during a 7-week feeding trial, before challenging fish with the bacterium Aeromonas salmonicida. We carried out two separate experiments to investigate fish survival and 24h post-infection to investigate the immediate response of free amino acid levels, and transcriptional changes in genes encoding urea cycle, NO cycle and polyamine synthesis enzymes. There were no differences in percentage fish mortality between diets, however there were numerous highly significant changes in free amino acid levels and gene expression to both dietary supplementation and infection. Out of 26 amino acids detected in blood plasma, 8 were significantly changed by infection and 9 by dietary supplementation of either arginine, ornithine or citrulline. Taurine, glycine and aspartic acid displayed the largest decreases in circulating levels in infected fish, while ornithine and isoleucine were the only amino acids that increased in concentration. We investigated transcriptional responses of the enzymes involved in arginine metabolism in liver and head kidney; transcripts for polyamine synthesis enzymes showed highly significant increases in both tissues across all diets following infection. The paralogous arginase-encoding genes, Arg1a, Arg1b, Arg2a and Arg2b, displayed complex responses across tissues and also due to diet and infection. Overall, these findings improve our understanding of amino acid metabolism following infection and suggests new potential amino acid targets for improving the immune response in salmonids.
Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA i... more Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA in the 1990s to the current 70 % plant-based diets with low levels of these fatty acids (FA). The aim of this study was to establish the impacts of low dietary EPA and DHA levels on performance and tissue integrity of Atlantic salmon (Salmo salar). Atlantic salmon (50 g) in seawater were fed fourteen experimental diets, containing five levels (0, 0•5, 1•0, 1•5 and 2•0 %) of EPA, DHA or a 1:1 EPA + DHA plus control close to a commercial diet, to a final weight of 400 g. Lack of EPA and DHA did not influence mortality, but the n-3-deficient group exhibited moderately slower growth than those fed levels above 0•5 %. The heart and brain conserved EPA and DHA levels better than skeletal muscle, liver, skin and intestine. Decreased EPA and DHA favoured deposition of pro-inflammatory 20 : 4n-6 and 20 : 3n-6 FA in membrane phospholipids in all tissues. When DHA was excluded from diets, 18 : 3n-3 and EPA were to a large extent converted to DHA. Liver, skeletal and cardiac muscle morphology was normal in all groups, with the exception of cytoplasm packed with large or foamy vacuoles and sometimes swollen enterocytes of intestine in both deficient and EPA groups. DHA supplementation supported normal intestinal structure, and 2•0 % EPA + DHA alleviated deficiency symptoms. Thus, EPA and DHA dietary requirements cannot be based exclusively on growth; tissue integrity and fish health also need to be considered.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2020
Functional amino acids (FAA) regulate metabolic pathways directly linked to health, survival, gro... more Functional amino acids (FAA) regulate metabolic pathways directly linked to health, survival, growth and development. Arginine is a FAA with crucial roles in protein deposition and the immune response. In mammals, supplementation of arginine's precursor amino acid, citrulline, is known to increase circulating arginine to levels beyond direct arginine supplementation, however, citrulline supplementation is poorly studied in fish. To address this knowledge gap, we supplemented the diet of rainbow trout with arginine and its precursor amino acids, ornithine and citrulline, at 3 levels (0.5%, 1% and 2% of the total diet) during a 14-week experiment. We sampled fish at 3h and 24h post-feeding to investigate immediate and steady-state effects, respectively. There were no differences in fish growth for any of the diets across a range of indicators. In blood plasma, out of 26 amino acids detected, 11 and 6 displayed significant changes 24h and 3h post-prandial, respectively. Arginine, ornithine and citrulline levels were all significantly increased by the citrulline supplemented diets. In muscle, 8 amino acids were significantly altered by supplemented diets, while there were no significant changes in liver. Arginine was increased by 2% citrulline supplementation in muscle tissue. We also investigated the transcriptional responses of urea cycle, nitric oxide cycle and rate-limiting polyamine synthesis enzymes, related to arginine's metabolism, in liver. At both time points, only 2 enzymes were significantly altered by the supplemented diets, however several significant changes were observed comparing 3h and 24h post-prandial expression levels. Of these, the paralogous polyamine synthesis enzyme encoding genes ODC1 and ODC2 displayed the largest increases in 3h post-prandial fish. These findings demonstrate that endogenous synthesis of arginine is possible from a citrulline supplemented diet and improve our understanding of arginine metabolism in fish.
-Omega-3 fettsyrer er helt sentrale for en rekke biologiske funksjoner i kroppen, som for eksempe... more -Omega-3 fettsyrer er helt sentrale for en rekke biologiske funksjoner i kroppen, som for eksempel cellenes oppbygging, avlesing av arvematerialet og inflammasjons-respons. Det er for øvrig relativt lite kunnskap om hvor lite omega-3 i fôret oppdrettslaksen kan klare seg med uten at det går ut over helse og velferd. Hensikten med dette prosjektet har dermed vært å øke kunnskapen om hvilke konsekvenser lave nivåer av EPA og DHA i fôret til laks, over store deler av livssyklus, vil ha for fiskens sammensetning og helse i seinere livsfaser. Prosjektet bygger på et fiskemateriale fra NFR prosjektet (224913), hvor atlantisk laks ble fôret med et fiskeoljefritt og fiskemelfritt fôr tilsatt ulike nivåer av EPA, DHA eller en kombinasjon av EPA og DHA fra en fiskestørrelse på 40g til 400g. I FHF prosjektet 900957 ble fisken fulgt videre i sjø på henholdsvis 0,2 %, 1 % og 1,7 % EPA og DHA i fôr fram til slaktestørrelse på ca. 3,5 kg. Resultater fra prosjektet tyder på at 1 % EPA og DHA i fôret, et nivå som tidligere var ansett som nedre behovsnivå, er for lavt til at fisken kan opprettholde god helse under krevende miljøbetingelser. Laks fôret på 1 % EPA og DHA eller lavere, døde i betydelig større grad enn laks fôret med 1,7 % av disse fettsyrene i fôret når fisken ble utsatt for gjentatt håndteringsstress som avlusning ved høye vanntemperaturer. Lave nivå av EPA og DHA i fôret førte bl.a. også til redusert nivå av astaxanthin og EPA og DHA nivå i muskel, økt mengde fett i lever og rundt innvoller, manglende virvelmellomrom i ryggrad og histologiske endringer i midttarm. Denne studien har også vist at lave nivåer av omega-3 i fôret har ulik innvirkning på sammensetningen av membranlipidene til ulike vev. Spesielt i skinnet blir DHA i veldig stor grad erstattet av arakidonsyre (20:4n-6) når DHA nivået reduseres. Samme trend ble observert for tarmens fosfolipider, men i mindre grad enn i skinnet. Lever er et av de mest konserverte vevene med tanke på EPA og DHA. For å sikre en robust laks i sjø, som tåler den håndteringen den møter under naturlig variasjoner i oppdrettsbetingelser, så tyder dataene fra prosjektet på at oppdrettslaksen må ha over 1 % marine omega-3 fettsyrer i fôret for å dekke sitt behov.The omega-3 fatty acids EPA and DHA are essential components in salmon diets due to their important biological functions. More knowledge is required about the minimum requirements that secures the health of Atlantic salmon throughout life. The aim of this project was to study the health consequences of using low dietary levels of EPA and DHA over much of the fish’s life cycle. The results shows that 1 % EPA and DHA in the diet of Atlantic salmon, a level previously regarded as the requirement level, is too low to maintain good health under demanding environmental conditions
Atlantic salmon were fed diets containing graded levels of EPA + DHA (1·0, 1·3, 1·6 and 3·5 % in ... more 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 tra...
The present study evaluated the effects of increasing the dietary levels of EPA and DHA in Atlant... more The present study evaluated the effects of increasing the dietary levels of EPA and 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...
Abstract For a rapidly developing aquaculture industry where availability of raw materials for di... more Abstract For a rapidly developing aquaculture industry where availability of raw materials for diet formulation are quickly changing, it is fundamental to define what are the dietary needs and benefits. In farming of Atlantic salmon (Salmo salar), highly unsaturated fatty acids (HUFA) are known to be essential, and a minimum dietary inclusion is needed. The aim of this study has been to map Atlantic salmon (Salmo salar) performance and midgut health towards dietary HUFA under normal and challenging condition. Atlantic salmon post-smolt at 150 g were fed four experimental diets over a feeding period of 10 weeks up to a final weight of 377 g followed by three weeks of unpredictable chronic stress (UCS). The diets varied in their HUFA level, with either 28.7 g/kg DHA (HDHA), 25 g/kg EPA (HEPA), 21.3 g/kg ARA (HARA) or 8.5 g/kg EPA + DHA (LHUFA). After the feeding period all fish had more than doubled their weight and fish fed HARA showed a significant lower specific growth rate compared to all other diets. Diets had little effect on intestinal morphology, barrier and transport function. Intestinal polar lipid composition suggested higher lipid metabolism in fish feed LHUFA and transcriptome analysis confirm upregulated lipid metabolism and downregulated energy turn over. The low dietary HUFA and high n6/n3 ratio had no major effect on Atlantic salmon performance and intestinal health. Comparing transcriptome profiles from HDHA to HEPA, more upregulated pathways are seen in fish fed HEPA, including metabolism and immunity. The fish feed HARA had downregulated turn-over and metabolism compared to fish fed HEPA. The UCS period resulted in zero growth and lower enterocyte height in all diet groups, and the intestinal barrier was reduced in the paracellular permeability to mannitol. Contradictory to previous studies, fish fed HDHA and HEPA responded to UCS with enhanced intestinal resistance. UCS also resulted in impaired intestinal transport by elevated ion flux and epithelial electrochemical gradient in fish fed LHUFA. Transcriptome pathway analysis indicated more cell turn over and lipid metabolism in LHUFA and HDHA. In conclusion, a low HUFA diet with 8.5 g/kg DHA + EPA can sustain growth and intestinal health under controlled condition, but the health is impaired after three weeks of chronic stress. Decreasing the n6/n3 ratio by increasing levels of EPA and DHA strengthens intestinal barrier in response to chronic stress. Increasing the ARA to HUFA ratio may have a negative effect on growth, but not on intestinal health.
The present study aimed to determine the minimum requirements of the essentialn-3 fatty acids EPA... more The present study aimed to determine the minimum requirements of the essentialn-3 fatty acids EPA and DHA in Atlantic salmon (Salmo salar) that can secure their health under challenging conditions in sea cages. Individually tagged Atlantic salmon were fed 2, 10 and 17 g/kg of EPA + DHA from 400 g until slaughter size (about 3·5 kg). The experimental fish reared in sea cages were subjected to the challenging conditions typically experienced under commercial production. Salmon receiving the lowest EPA + DHA levels showed lower growth rates in the earlier life stages, but no significant difference in final weights at slaughter. The fatty acid composition of various tissues and organs had remarkably changed. The decreased EPA + DHA in the different tissue membrane phospholipids were typically replaced by pro-inflammatoryn-6 fatty acids, most markedly in the skin. The EPA + DHA levels were maintained at a higher level in the liver and erythrocytes than in the muscle, intestine and skin. ...
Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA i... more Farmed salmon feeds have changed from purely marine-based diets with high levels of EPA and DHA in the 1990s to the current 70 % plant-based diets with low levels of these fatty acids (FA). The aim of this study was to establish the impacts of low dietary EPA and DHA levels on performance and tissue integrity of Atlantic salmon (Salmo salar). Atlantic salmon (50 g) in seawater were fed fourteen experimental diets, containing five levels (0, 0·5, 1·0, 1·5 and 2·0 %) of EPA, DHA or a 1:1 EPA+DHA plus control close to a commercial diet, to a final weight of 400 g. Lack of EPA and DHA did not influence mortality, but the n-3-deficient group exhibited moderately slower growth than those fed levels above 0·5 %. The heart and brain conserved EPA and DHA levels better than skeletal muscle, liver, skin and intestine. Decreased EPA and DHA favoured deposition of pro-inflammatory 20 : 4n-6 and 20 : 3n-6 FA in membrane phospholipids in all tissues. When DHA was excluded from diets, 18 : 3n-3 an...
Comparative Biochemistry and Physiology Part A: Physiology, 1994
Atlantic cod (0.8-2.5 kg) were transferred from 8OC to l°C seawater for 17 days. No fish died. Ex... more Atlantic cod (0.8-2.5 kg) were transferred from 8OC to l°C seawater for 17 days. No fish died. Exposure to l°C water produced no changes in hematocrit, or in plasma concentrations of Cl-or Mg '+ Cold water exposure caused a marked increase in plasma cortisol and. glucose concentrations. Fish in l°C seawater had higher gill Na-K-ATPase activity than fish in 8OC seawater, whereas there were no differences in gill lipid class or fatty acid composition.
Thesis (Ph. D.)--Norwegian University of Science and Technology, Trondheim, 1997. Includes biblio... more Thesis (Ph. D.)--Norwegian University of Science and Technology, Trondheim, 1997. Includes bibliographical references.
Initial levels of white muscle high-energy phosphates, IMP, ATP:IMPratio, adenylate energy charge... more Initial levels of white muscle high-energy phosphates, IMP, ATP:IMPratio, adenylate energy charge and pH were used as indicators of handling stress when Atlantic salmon were slaughtered. Ante-mortem handling included fish that were either anesthetized (baseline), quickly netted and killed by a blow to the head (unstressed) or chased to exhaustion in the holding tank (stressed). During subsequent storage in ice, freshness was evaluated in terms of IMP, HxR, Hx and K-values. HPLC showed initial differences in distribution of metabolites induced by struggling gradually fell during storage. K-values were different only for 2 days post mortem, but the effect of handling stress was discernible as higher mean K-values and different IMP and HxR contents for up to 7 days post mortem.
Oily fish are an important source of health promoting nutrients such as the very long chain marin... more Oily fish are an important source of health promoting nutrients such as the very long chain marine omega-3 (VLC-n3) fatty acids and simultaneously a source of potentially hazardous contaminants. Fish oils that are used in fish feed are the main source for both contaminants and VLC-n3. Decontamination techniques have recently been developed to effectively remove persistent organic contaminants from fish oils. The aim of the present study was to assess the level of potentially hazardous contaminants and the health beneficial fatty acids in Atlantic salmon reared on novel decontaminated feeds. Atlantic salmon were fed for 18 months (an entire seawater production cycle) on diets based on decontaminated or non-treated (control) fish oils until market size ($5 kg). The level of known notorious persistent organic pollutants (POPs, i.e. dioxins, dioxin-like polychlorinated biphenyls (DL-PCBs), non dioxin-like PCBs, poly brominated diphenyl ethers (PBDE), and organochlorine pesticides), as well as fatty acid composition were analysed in fish oils, the two diets, and Atlantic salmon fillet. The oil decontamination process was a two-step procedure using active carbon and short path distillation. The fillet levels of POPs in market size fish were reduced by 68-85% while the concentration of very long chain omega-3 fatty acids was reduced by 4-7%. No differences in biomarkers of dioxin-like component exposures, such as hepatic gene expression of CYP1A or AhR2B, CYP1A protein expression and 7-ethoxyresorufin O-deethylase (EROD) activity, were observed between salmon raised on normal or decontaminated feeds, thus indicating that the difference in POPs levels were of no biological significance to the fish. Atlantic salmon reared on decontaminated feeds had sum polychlorinated dibenzodioxins/furans (PCDD/Fs) and DL-PCB concentrations that were comparable with terrestrial food products such as beef, while the level of marine omega-3 fatty acids remained as high as for commercially farmed Atlantic salmon.
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