Atlantic Salmon Protein Research Articles

Comparing feces collection methods for evaluating the apparent digestibility coefficient of brewers' spent yeast in juvenile Atlantic salmon (Salmo salar).

Brewer's spent yeast (BSY), derived from Saccharomyces cerevisiae used in beer production, is a valuable protein source for aquafeeds. Estimations of apparent digestibility coefficients (ADC) for nutrients in BSY are crucial for its inclusion in aquafeeds. ADC estimations for Saccharomyces cerevisiae protein in rainbow are hardly comparable from a methodological point of view, whereas the ADC estimations for BSY protein in Atlantic salmon are only based on stripped feces, which are known to produce underestimations. Therefore, new determinations of ADC of BSY nutrients are necessary for the inclusion of this ingredient in practical diets for salmonids. This study is focused on determining unbiased ADC values for protein and energy from BSY in juvenile Salmo salar. To reduce systematic biases, fecal samples were collected using stripping and decantation methods, which are known to produce under-and overestimations, respectively. 780 fish (25.16 ± 4.88 g) were stocked in six tanks. A reference diet (50% protein, 20% lipid, 1% Cr2O3) was provided to three tanks, and a test diet (70,30 reference diet to BSY) to the other three. ADC for BSY protein was 84.70 ± 1.04% (decantation) and 70.50 ± 4.03% (stripping). For gross energy, stripped feces yielded an ADC of 52.04 ± 5.30%, while decantation resulted in 63.80 ± 1.17%. Thus, ADC estimates were taken as the average of the stripping-value and the decantation-value, resulting in 77.6% for BSY crude protein, which is appreciably higher than previously measured values in S. salar fed undisrupted S. cerevisiae, and in 57.9% for gross energy.

Replacing fishmeal with plant protein in Atlantic salmon (Salmo salar) diets by supplementation with fish protein hydrolysate

The effects of feeding an 80% plant protein diet, with and without fish protein hydrolysate (FPH) supplementation, on the growth and gut health of Atlantic salmon were investigated. Fish were fed either (A) a control diet containing 35% fishmeal, (B) an 80% plant protein diet with 15% fishmeal, (C) an 80% plant protein diet with 5% fishmeal and 10% partly hydrolysed protein, or (D) an 80% plant protein diet with 5% fishmeal and 10% soluble protein hydrolysate. Fish on the 80% plant- 15% fishmeal diet were significantly smaller than fish in the other dietary groups. However, partly-hydrolysed protein supplementation allowed fish to grow as well as fish fed the control 35% fishmeal diet. Fish fed the FPH diets (diets C and D) had significantly higher levels of amino acids in their blood, including 48% and 27% more branched chain amino acids compared to fish on the 35% fishmeal diet, respectively. Plant protein significantly altered gut microbial composition, significantly decreasing α-diversity. Spirochaetes and the families Moritellaceae, Psychromonadaceae, Helicobacteraceae and Bacteroidaceae were all found at significantly lower abundances in the groups fed 80% plant protein diets compared to the control fishmeal diet.

Net production of Atlantic salmon (FIFO, Fish in Fish out < 1) with dietary plant proteins and vegetable oils

Adult Atlantic salmon (Salmo salar; approximately 800 g start weight) were fed diets with a high replacement of fish meal (FM) with plant proteins (70% replacement), and either fish oil (FO) or 80% of the FO replaced by olive oil (OO), rapeseed oil (RO) or soybean oil (SO) during 28 weeks in triplicate. Varying the lipid source only gave non-significant effects on growth and final weight. However, a significantly reduced feed intake was observed in the SO fed fish, and both feed utilization and lipid digestibility were significantly reduced in the FO fed fish. Limited levels of dietary 18:3n-3, precursor to EPA and DHA, resulted in no net production of EPA and DHA despite increased mRNA expression of delta-5-desaturase and delta-6-desaturase in all vegetable oil fed fish. Net production of marine protein, but not of marine omega-3 fatty acids, is thus possible in Atlantic salmon fed 80% dietary vegetable oil and 70% plant proteins resulting in an estimated net production of 1.3 kg Atlantic salmon protein from 1 kg of FM protein. Production of one 1 kg of Atlantic salmon on this diet required only 800 g of wild fish resources (Fish in - Fish out < 1).

Astaxanthin binding protein in Atlantic salmon

The rubicund pigmentation in salmon and trout flesh is unique and is due to the deposition of dietary carotenoids, astaxanthin and canthaxanthin in the muscle. The present study was undertaken to determine which protein was responsible for pigment binding. Salmon muscle proteins were solubilized by sequential extractions with non-denaturing, low ionic strength aqueous solutions and segregated as such into six different fractions. Approximately 91% of the salmon myofibrillar proteins were solubilized under non-denaturing conditions using a protocol modified from a method described by Krishnamurthy et al. [Krishnamurthy, G., Chang, H.S., Hultin, H.O., Feng, Y., Srinivasan, S., Kelleher. S.D., 1996. Solubility of chicken breast muscle proteins in solutions of low ionic strength. J. Agric. Food Chem. 44: 408–415.] for the dissolution of avian muscle. To our knowledge, this is the first time this solubilization approach has been applied to the study of molecular interactions in myofibrillar proteins. Astaxanthin binding in each fraction was determined using an in vitro binding assay. In addition, SDS-PAGE and quantitative densitometry were used to separate and determine the relative amounts of each of the proteins in the six fractions. The results showed that α-actinin was the only myofibrillar protein correlating significantly ( P < 0.05) with astaxanthin binding. Alpha-actinin was positively identified using electrophoretic techniques and confirmed by tandem mass spectroscopy. Purified salmon α-actinin bound synthetic astaxanthin in a molar ratio of 1.11:1.00. The study was repeated using halibut α-actinin, which was found to have a molar binding ratio of astaxanthin to α-actinin of 0.893:1. These results suggest that the difference in pigmentation between white fish and Atlantic salmon is not due to binding capacity in the muscle, but rather differences in the metabolism or transport of pigment.

Maintenance threonine requirement and efficiency of its use for accretion of whole-body threonine and protein in Atlantic salmon (Salmo salar L.) fry

Eighteen groups of seventy Atlantic salmon (Salmo salar L.) fry (initial mean body weight 0.8 (sd 0.01) g) were fed on semi-purified diets containing graded levels of l-threonine (Thr) in 15 litres aquaria at a temperature of 14.5+/-1 degrees C. Doses of Thr represented 1, 31, 41, 51, 62, 72, 83 and 93 % of its ideal level for optimum protein deposition. Indispensable amino acids other than Thr were included in the same proportion (on a g/16 g N basis) as in the Atlantic salmon fry whole-body carcass. Following 36 d of feeding and a 36 h fast, fry were killed for whole-body protein and amino acid analysis. Weight gain (r2 0.98), protein accretion (r2 0.97), and Thr accretion (r2 0.97) were linear (P<0.01) functions of Thr intake. Slope of the Thr accretion regression line showed that the efficiency of Thr utilisation above maintenance was 76 %. At zero Thr intake, fry lost 5.4 mg Thr/kg body weight0.75 per d. The Thr maintenance requirement was 7.2 mg/kg body weight0.75 per d and the Thr requirement for growth was 66 mg for 1 g protein deposition. Increasing doses of Thr resulted in increased (P<0.05) concentrations of histidine and lysine, and decreased concentrations of isoleucine in whole-body protein. The maintenance need for Thr represented 13.4 % of the total need for Thr. The data suggest that efficiency of Thr utilisation above maintenance is constant at all levels of Thr intake between 1 and 93 % of the level required for optimum protein deposition.

Molecular characterization of a PDZ-LIM protein in Atlantic salmon (Salmo salar): a fish ortholog of the alpha-actinin-associated LIM-protein (ALP).

A protein containing both PDZ and LIM protein-protein interaction motifs has for the first time been identified in a lower vertebrate species. A full-length cDNA encoding the ortholog of the alpha-actinin-associated LIM protein (ALP) was isolated from white skeletal muscle of Atlantic salmon (Salmo salar). Whereas ALP is expressed as two muscle specific isoforms in mammals and chicken as the result of alternative splicing, a single ALP transcript was found in both muscle and non-muscular tissues of Atlantic salmon. On the other hand, Western blot analysis revealed several immunoreactive ALP variants in salmon muscle tissues, including a 45 kDa protein in white and red skeletal muscle and a 37-40 kDa protein in heart and smooth muscle. Salmon ALP and alpha-actinin showed similar striated patterns in serial longitudinal sections of white and red skeletal muscle and heart muscle. Expression of ALP was initiated at the 45-somite stage of the salmon embryogenesis contemporary with the first appearance of alpha-actinin transcripts. The similarities in both the spatial and temporal expression patterns of salmon ALP and alpha-actinin strongly indicate that the two proteins are associated as in higher vertebrates, and that the assumed involvement of ALP in the organization and/or maintenance of the Z-lines in striated muscle has been conserved during vertebrate evolution. However, in contrast to the restricted expression of ALP in higher vertebrates, the ubiquitous expression of salmon ALP suggest that this factor is involved in the assembly of additional multi-protein complexes in fish.

White muscle free amino acid concentrations following feeding a maize gluten dietary protein in Atlantic salmon ( Salmo salar L.)

This study aimed to investigate the effect of high maize gluten protein diets on the white muscle free amino acid (FAA) concentrations of Atlantic salmon following feeding and to examine whether these tissue free amino acids profiles highlighted any dietary deficiencies in essential amino acids (EAA). Two isocaloric and isonitrogenous diets (52% protein, 20% oil) were formulated and mixed proportionately to give a total of five feeds in which maize gluten provided 0%, 16%, 32%, 48% and 64% of the total dietary protein (diets 0MG, 16MG, 32MG, 48MG, 64MG, respectively). Triplicate groups of 19 g Atlantic salmon were fed each of the experimental diets for a period of 40 days. At the end of the growth experiment, groups of four salmon from each diet were taken at 4, 8 and 12 h after feeding for the white muscle amino acids analysis. Although fish doubled their weights during the growth period, no significant differences were observed in specific growth rates, feed conversion ratios, protein digestibility and protein growth rates among fish fed the test diets. Total free amino acid (FAA) concentrations did not change at various times after a meal and this was also true for the majority of individual FAAs (except asparagine, which increased significantly 12 h after feeding). The most notable diet-induced changes in the white muscle were an overall reduction in essential FAA concentrations (threonine and lysine) as dietary maize gluten content increased and an increase in histidine and leucine. Correlations between dietary essential amino acids patterns and white muscle protein-bound amino acids were examined. The possibility of partial replacement of fish meal maize gluten up to 50% was demonstrated.

Turnover of α-, γ, and δtocopherol and distribution insubcellular and lipoprotein fractions indicate presence of an hepatic tocopherolbinding protein in Atlantic salmon (Salmo salar L.)

The purpose of this work was to study the turnover of a, γ andδtocopherol (TOH) in Atlantic salmon (Salmo salar, L.). Fish induplicate tanks were fed a diet containing 150 mg kg-1α-TOH and 100 mg kg-1 each of γ and δTOHadded as tocopheryl acetates. After fillet TOH concentrations had adjustedto the dietary supplementation levels, samples were taken from fish that hadbeen deprived of feed for 100 h, and from fish that had been fed regularlyuntil sampling. The retained levels of tocopherols in plasma correspondedgrossly with their biological activities, as found in experiments withmammals (α:γ:δ≈100: 20:3). The plasma concentrationsof α-, γ and δTOH amounted to 65, 44 and 15%,respectively, in unfed compared to fed fish. Very low density lipoprotein(VLDL), appeared to contain a greater fraction of plasma α-TOH than ofplasma δTOH. The mitochondrial fraction of liver, but not that of darkmuscle, was highly enriched in α-TOH, and less in γ andδTOH. The concentration ratios in liver and bile indicate thatδ, and to some extent, γTOH are excreted in the bile at a higherrate than α-TOH. The data fit the hypothesis that Atlantic salmonliver contains a tocopherol binding protein with higher affinity forα-TOH than for the other tocopherol homologues. This appears toprevent excretion of α-TOH in the bile, and stimulate incorporation ofα-TOH in VLDL for subsequent secretion into the blood stream. As aconsequence, α-TOH is retained in the body to a greater extent thanγ and α-TOH.

HP8 The complement component C3 is produced by hepatocytes and behave as an acute-phase protein in atlantic salmon, Salmo Salar, after injection of β-glucan

HP8 The complement component C3 is produced by hepatocytes and behave as an acute-phase protein in atlantic salmon, Salmo Salar, after injection of β-glucan

Differences in digestion and absorption of dietary protein in Atlantic salmon (Salmo salar) with genetically different trypsin isozymes

Digestion and absorption of dietary protein were studied through facilitation of amino acid in the plasma and white muscle after a single feeding. The comparison was made between Atlantic salmon with and without trypsin isozyme TRP-2*92. Higher absorption of dietary protein was associated with the presence of the isozyme, as the post-prandial total levels of free amino acids (FAA) in both plasma and white muscle were significantly higher in salmon with the isozyme than those in salmon without it. Higher digestion rate of the dietary protein in salmon carrying the isozyme was indicated by faster elevation of essential FAA in the plasma and of overall FAA in their white muscle. Other indications which suggest differences in nitrogen metabolism between salmon with and without the isozyme were the observations of significant differences in (a) the levels of lysine, hydroxyproline, alanine, aspartic acid, β-alanine, threonine, valine and a nitrogen-containing compound taurine in plasma, and (b) the levels of alanine, glutamic acid, glycine and anserine in white muscle. Trypsin activity in the pyloric caeca showed less response to feeding than that in the intestine, but it may have consequence for growth as its activity was significantly higher in growing fish than in non-growing fish.

Differences in digestion and absorption of dietary protein in Atlantic salmon (Salmo salar) with genetically different trypsin isozymes

Digestion and absorption of dietary protein were studied through facilitation of amino acid in the plasma and white muscle after a single feeding. The comparison was made between Atlantic salmon with and without trypsin isozyme TRP‐2*92. Higher absorption of dietary protein was associated with the presence of the isozyme, as the post‐prandial total levels of free amino acids (FAA) in both plasma and white muscle were significantly higher in salmon with the isozyme than those in salmon without it. Higher digestion rate of the dietary protein in salmon carrying the isozyme was indicated by faster elevation of essential FAA in the plasma and of overall FAA in their white muscle. Other indications which suggest differences in nitrogen metabolism between salmon with and without the isozyme were the observations of significant differences in (a) the levels of lysine, hydroxyproline, alanine, aspartic acid, β‐alanine, threonine, valine and a nitrogen‐containing compound taurine in plasma, and (b) the levels of alanine, glutamic acid, glycine and anserine in white muscle.Trypsin activity in the pyloric caeca showed less response to feeding than that in the intestine, but it may have consequence for growth as its activity was significantly higher in growing fish than in non‐growing fish.

Genetic differences in digestion and absorption of dietary protein in Atlantic salmon, Salmo salar L., with different trypsin isozyme patterns

. In the genetical presence of trypsin isozyme TRP-2(92), Atlantic salmon, Salmo salar L., of either 100g or 400g in weight showed similarity in significantly higher absorption of the dietary protein as their postprandial total free amino acids in the plasma were significantly higher than those in the salmon without the isozyme. Better digestion of the dietary protein was observed by the presence of significantly higher postprandial plasma lysine level of the TRP-2(92) salmon. Another indication of different protein metabolism between salmon with and without the isozyme was observed by differences in plasma alanine and hydroxyproline. Trypsin activity in the intestine showed a higher response to feeding than that in the pyloric