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Notes: Two size groups (0.5 and 3 kg) of Atlantic salmon, Salmo salar L., were stressed by netting and transport from sea cages into land-based tanks. Handling lasted for 1 h. Before onset of stress, basal concentrations of haematocrit and haemoglobin, plasma cortisol and glucose, and liver and muscle glycogen were measured. All levels were within ranges reported for salmon. After handling and at chosen time intervals during recovery, samples were taken to judge the impact of handling and whether secondary changes in carbohydrate metabolism were related of fish size. A low cortisol peak indicated a mild stress reaction after handling independent to fish size. Plasma glucose peaked as cortisol declined, and returned to basal levels within 48 h. Liver glycogen seemed to be the main source of plasma glucose. No changes were measured in muscle glycogen concentrations. The results indicate a high tolerance to handling stress in Atlantic salmon independent of fish size.

Notes: This publication reports on analytical data from a large-scale experiment, using 3360 Atlantic salmon, Salmo salar L., distributed into 12 sea cages. Salmon were grown from an average 600 g to an average 3.5 kg. Samples for analyses were taken when fish were in the range of 1.8 and 3.5 kg. Dietary changes between groups were increased starch from 24 to 230 g kg−1 and balanced with protein. The diets were isolipic.All salmon showed small stores of glycogen in all analysed organs, and only in heart, gills and kidney of large fish (3.5 kg) were the levels correlated with dietary starch. Minor differences between groups were found in liver NADPH production, but with substantially decreased NADPH production per g protein as the fish grew from 1.8 to 3.5 kg, indicating that increasing dietary starch did not lead to induction of liver hexokinase, and that the activity of this enzyme may decline as fish size increases.An increase in plasma glucose concentrations was found as dietary starch increased, but all levels were moderate and ranged within reference values. Plasma total protein concentrations did not, however, vary according to decreased dietary protein, but increased substantially in all groups as the fish grew from 1.8 to 3.5 kg. Dietary treatments had no influence on haematological parameters, except for decreased haemoglobin concentrations as dietary starch increased in large fish (3.5 kg). No impared liver function was detected, evaluated by activities of ASAT, ALAT and LDH, and by histological analyses. Low serum lysozyme activities were recorded in all groups, and were not correlated with plasma glucose or liver glycogen concentrations.

Notes: Eighty turbot, Scophthalmus maximus (L.), (average weight 61 g) were injected intraperitoneally with exactly 1 g glucose per kg body weight. There was a peak in plasma glucose 3 h post injection. Thereafter a gradual decrease to basal levels was seen within 24 h. Plasma triacylglycerol concentrations showed a rapid decline during the first 24 h, and thereafter stable values. Blood haematocrit values decreased from 20% before injection to 16% 72 h after injection. Liver glycogen concentrations showed an initial decrease from 8 to 5 g 100 g−1 (w.w) during the first 12 h, and thereafter stable values, while muscle glycogen concentrations increased during the first 12 h, and thereafter showed a gradual decline until 72 h. This response was most probably caused by secondary changes upon handling in combination with the direct response to a glucose load. Thus turbot was able to restore alterations in carbohydrate metabolism efficiently within 24 h.

Notes: The utilisation of dietary carbohydrates and their effects on fish metabolism are reviewed. Details on how dietary carbohydrates affect growth, feed utilisation and deposition of nutrients are discussed. Variations in plasma glucose concentrations emphasizing results from glucose tolerance tests, and the impact of adaptation diets are interpreted in the context of secondary carbohydrate metabolism. Our focus then shifts to selected aspects of hormonal regulation of carbohydrate metabolism and dietary carbohydrates and their variable effects on glycogen and glucose turnover. We analyse the interaction of carbohydrates with other nutrients, especially protein and protein sparing, and de novo synthesis of lipids, and finish by discussing the correlation of dietary carbohydrates with fish health.

Notes: To determine seasonal variation in growth and feed conversion ratio (FCR), Atlantic salmon postsmolts (Salmo salar L.) were exposed to either simulated natural photoperiod (SNP) for 12 months or continuous light (LL) from January to June followed by SNP until December. Feed was given to excess and uneaten feed pellets were collected after every meal for estimation of feed intake and calculation of FCR. Body weight increased from 1086 ± 9 g (mean ± SEM) in January to 4970 ± 7 g (SNP) and 5190 ± 23 g (LL) in December. Specific growth rate (SGR), condition factor and feed intake displayed strong seasonal variation in both groups. Measurements of the thermal growth coefficient correlated highly with SGR (r = 0.98, P 〈 0.05), indicating that the seasonal variation in SGR was independent of temperature and fish size. Continuous light treatment resulted in increased growth from spring, while the fish exposed to simulated natural light had increased growth rate in late summer. Furthermore, LL improved FCR. Periods of high SGR were concurrent with periods of low FCR in both groups.

Notes: In order to investigate how seasonal variation in growth affects selected fillet quality parameters, immature Atlantic salmon (Salmo salar L.) were reared under simulated natural photoperiod (SNP) for 12 months or continuous light (LL) from January to June followed by SNP until December. Photoperiod treatments advanced the growth rate pattern of the LL group compared with the SNP group and influenced macronutrient metabolism, evaluated both as trends in protein and lipid retention and in fillet lipid and protein levels. Good growth was associated with low fillet lipid and protein level, in addition to reduced levels of fillet tocopherol and astaxanthin, indicating increased oxidative stress. Elevated levels of thiobarbituric reactive substances (TBARs) further supported this. Slaughtering during periods of high growth may therefore reduce postmortem quality, both because of increased susceptibility to fillet lipid peroxidation and reduced astaxanthin levels, which were lowered in vivo and might consequently be depleted further after slaughter. Specialized use of antioxidant-rich feed prior to slaughter is suggested if slaughtering is expected to occur during periods of high growth rate.

Notes: Accumulation of 14C in various tissues and organs was studied in three different groups of 0.8-kg Atlantic salmon Salmo salar force-fed with 14C1-glucose in order to evaluate if metabolism of glucose depended on adaptation to dietary carbohydrate level. The salmon had been fed diets supplemented with 0, 100 and 200 g maize dextrin kg−1 for 10 months before the experiment. The fish were force-fed 6.65 × 104 Bq of 14C1 glucose kg−1 BW, in gelatin capsules. Fish for analysis were obtained 16 h later. 14C was measured in blood plasma, gill, kidney, liver and white muscle, and in lipid extract of liver.The liver contained most 14C, followed by heart, blood plasma, gill and liver lipid extract, while kidney and muscle contained the least 14C per gram or millilitre tissue. The muscle contained most radioactivity, on an estimated total tissue basis, followed by liver, blood plasma, gill, liver lipid extract, kidney and heart tissue. Thirty-eight per cent of the orally administered 14C was recovered in the salmon adapted to the diet without dextrin after 16 h. This was significantly (P 〈 0.05) higher than the 30% and 32% recovered in the salmon adapted to diets with 10% and 20% dextrin. This effect on adaptation to dietary dextrin level in glucose uptake or metabolism was supported by a trend (P 〈 0.10) toward higher radioactivity per gram or millilitre of each individual tissue in the fish adapted to the diet without dextrin, when compared with the other two adaptation regimes.

Notes: Atlantic halibut larvae were fed docosohexanoic acid- (DHA) selco enriched Artemia (RH-cysts) or wild zooplankton in duplicate tanks from first-feeding and 60 days onward. The zooplankton were collected from a fertilized sea water pond and consisted mainly of different stages of Eurytemora affinis and Centropages hamatus. There were no differences in survival, or in growth during the first 45 days of feeding, between larvae fed the two prey items, but the larvae fed Artemia showed much higher incidence of malpigmentation and impaired eye migration than larvae fed zooplankton. The prey organisms contained similar amounts of dry matter and protein, but Artemia was higher in lipid and glycogen than the zooplankton. Larvae fed Artemia were higher in both glycogen and lipid than the zooplankton-fed larvae towards the end of the feeding period. There were large differences between the prey organisms in the concentrations of essential fatty acids (% of total fatty acids) which was reflected in the fatty acid composition of the larval body. It is concluded that the macronutrient composition of Artemia in the present study was probably within the optimal range for promotion of growth and survival in young Atlantic halibut. The concentration of n-3 HUFA, and especially DHA, is however, very much lower in enriched Artemia than in copepods, and may be one of the factors triggering developmental errors in Atlantic halibut.

Notes: This study was conducted to investigate the long-term effects of feeding plant products from both traditional breeding and from biotechnology on intestinal somatic indices, histology and cell proliferation in first-feeding Atlantic salmon, Salmo salar L. (initial weight 0.21 ± 0.02 g). A standard fishmeal diet (standard fishmeal) was formulated to contain fishmeal as the sole protein source and suprex maize as the main starch source. Six experimental diets were then developed: two in which some of the fishmeal was replaced with commercially available, genetically modified Roundup Ready® full-fat soybean meal (GM-soy) or commercially available, non-GM full-fat soybean meal (nGM-soy) at a level of 12.5% of the total diet, and four diets in which the suprex maize was replaced with two lines of GM-maize (Dekalb 1; D1 and Pioneer 1; P1), both products of event MON810, and their half-sibling non-GM counterparts (Dekalb 2; D2 and Pioneer 2; P2), at a level of 12.1% of total diet. Each diet was fed to fish in triplicate tanks and the experiment lasted for 8 months, during which the fish reached a final weight of 101–116 g. There was no significant effect of diet on the intestinal indices, nor were histological changes observed in the pyloric caeca or mid intestine. In the distal intestine, one of nine sampled fish fed nGM-soy showed moderate changes, two of nine sampled fish fed GM-soy showed changes, one with moderate and one with severe changes, and two of nine fish fed nGM-maize D2 had moderate changes. Using a monoclonal antibody against proliferating cell nuclear antigen (PCNA), cell proliferative responses to the experimental diets were assessed. In fish fed both soy diets, a significantly higher (P 〈 0.05) cell proliferation response was observed in the distal intestine concomitant with an increased localization of PCNA positive cells along the whole distal intestinal folds. The PCNA response among the nGM-soy group was significantly higher compared with all the other diet groups. In contrast, for fish exposed to dietary maize (type D) compared with fish fed the standard fishmeal, the soy-diets (GM-soy and nGM-soy) and maize (type P), a significantly lower (P 〈 0.05) cell proliferation response was observed in the distal intestine. Results indicated that the GM plant products investigated in this study, at about 12% inclusion level, were as safe as commercially available non-GM products, at least in terms of their effect on indices and histological parameters of the Atlantic salmon intestinal tract.

Notes: A 56-day growth trial was conducted to study the utilization of hydrolysed potato starch by juvenile Atlantic salmon Salmo salar L. using a restricted feeding regime. Two diets supplemented with either 15% or 30% hydrolysed potato starch and a control diet without carbohydrate supplementation were each fed to triplicate groups of salmon. Feeding rate varied from 1.4% to 2.0% of body weight per day, so that fish were fed similar amounts of protein and lipid. In spite of the restricted feeding used, no growth stimulation was measured as a consequence of the additional starch intake. No variation was found in protein utilization, measured as protein efficiency ratio values (PER), while feed utilization showed decreased values as starch intake increased. Plasma glucose concentrations did not vary as a consequence of increased starch intake when measured 24 h after feeding, indicating efficient regulation of plasma glucose. In fish fed the 30% starch, the plasma triacylglycerol concentration was significantly increased, which may point to de novo lipid synthesis from the high starch intake. No variation was found in plasma cholesterol or protein concentrations, or asparagine aminotransferase, alanine aminotransferase and lactate dehydrogenase activities. This shows that the fish health status and liver function were normal (no mortality was registered). Liver and muscle showed increased glycogen levels as a function of increased starch intake. The same diets were also fed to juvenile white sturgeon Acipencer transmontanus and hybrid tilapia Oreochromis niloticus×O. aureus. These results are presented separately.