Kaare Julshamn

Effects of dietary selenite or selenomethionine on tissue selenium levels of Atlantic salmon (Salmo salar)

Abstract A feeding experiment was carried out to compare the effects of supplementing a fish meal based diet with selenium as selenite or selenomethionine on Atlantic salmon. Five duplicate groups of Atlantic salmon parr (mean weight 4.5 g) were given a basal diet either unsupplemented or supplemented with 1 and 2 mg Se/kg as selenite or selenomethionine respectively, for 8 weeks. Weight gains were similar in all groups. Selenium concentrations in the liver were highest in the groups given selenite whereas muscle and whole-body selenium concentrations were highest in the groups given selenomethionine. Only a minor increase in muscle selenium concentration was observed by supplementing selenite. There were no significant differences in activity of the selenium-containing enzyme, glutathione peroxidase, between the dietary groups, indicating a sufficient selenium status in all groups.

Assessment of zinc status in juvenile Atlantic salmon (Salmo salar) by measurement of whole body and tissue levels of zinc

Abstract Duplicate groups of 40 g Atlantic salmon were fed dry pelleted diets based on cod muscle meal as a protein source for 8 weeks. The basal diet contained 17 mg Zn/kg to which 0, 10, 20, 40 or 80 mg Zn/kg diet, respectively, were added as ZnSO4·7H2O. After 8 weeks, 15 fish from each dietary treatment were marked and then they were fed the basal diet for another 4 weeks. Fish were sampled after 2, 4, 8 and 12 weeks. Blood samples were withdrawn and serum was analyzed for zinc concentration and alkaline phosphatase (AP) activity. Liver, kidney, vertebrae and intestine were removed from ten fish in each dietary treatment. A further ten fish were used for whole body mineral analyses. There were no significant differences in growth due to different dietary zinc concentrations and this, together with data on alkaline phosphatase and iron levels, showed that the basal diets contained sufficient zinc to prevent overt zinc deficiency symptoms. Zinc concentrations in the whole body and tissues, however, were significantly influenced by dietary zinc level. On the basis of the dietary zinc concentration required to maintain whole body zinc and serum zinc concentrations within the normal range, it was concluded that the dietary zinc requirement of juvenile Atlantic salmon is between 37 and 67 mg Zn/kg dry diet under our test conditions. Hence, until more data are available, juvenile Atlantic salmon diets based almost entirely on marine fish protein should contain > 67 mg Zn/kg dry diet.

Effect of dietary copper on the hepatic concentration and subcellular distribution of copper and zinc in the rainbow trout (Salmo gairdneri)

Abstract Feeding trials were conducted with six groups of rainbow trout (mean initial weight of 35 g) using purified diets with an estimated gross energy of 1442 kJ 100 g and copper contents ranging from 3.5 to 1000 mg Cu/kg diet. With the exception of groups 1 and 2 (given 102 and 194 mg Cu/kg), which showed an atypical growth response, the weight gain and feed conversion were reduced with increasing levels of Cu in the diet. No gross pathologies and very low mortalities were noted even in the group receiving the highest dietary copper level. Copper and zinc were determined in freeze-dried samples and in subcellular fractions from individual trout livers using atomic absorption spectrophotometry. A linear relationship was observed between liver copper concentration and copper provided in the diet. Copper intake had no effect on hepatic zinc concentration. Increased dietary copper also gave increased copper levels in whole fish but the concentration factor was much lower than in the liver. The relative retention of copper given at levels above 100 mg Cu/kg dry diet was low and was estimated to be 1.3%. Subcellular fractionation studies demonstrated that 43–67% and 36–49%, respectively, of hepatic copper and zinc were sedimented with the fractions nuclei, mitochondria and lysosomes. Increased dietary levels of copper had apparently no effect on the subcellular distribution of zinc except at the highest level (group 6) where an increase in zinc recovered in the nuclear fraction was observed.

Optimization of the determination of selenium in marine samples by atomic absorption spectrometry: Comparison of a flameless graphite furnace atomic absorption system with a hydride generation atomic absorption system

Abstract A comparison has been made between a graphite furnace system based on nickel as a matrix stabilizing metal and an automated hydride generation system with a heated quartz cell. The effect of nickel as a matrix modifier was studied in pure selenite solutions as well as in biological matrixes by different charring temperatures. The suppression effect of different acids on the response of the analyte is reported and discussed. The use of an electrically heated quartz tube as an alternative to the argon hydrogen flame method unproved the selenium determination by hydride generation atomic absorption. The effect of hydrochloric acid to secure quantitative formation of selenium (IV) and the interference of copper in the response measurements have been studied. Further a comparison has been made between three different digestion procedures when the hydride generation atomic absorption system was applied. The results of the graphite furnace atomic absorption and the hydride generation atomic absorption were found to be equally accurate, but the graphite furnace technique gave better reproducibility.

Distribution of trace elements from industrial discharges in the Hardangerfjord, Norway : A multivariate data analysis of saithe, flounder and blue mussel as sentinel organisms

Arsenic, copper, zinc, cadmium, lead and mercury were determined in the muscle and liver of two species of fish, saithe (Gadus virens) and flounder (Platichthys flesus), and in the soft tissues of blue mussels (Mytilus edulis). These were sampled from eight locations along the Hardangerfjord up to 100 km from the source of the pollution at the head of the fjord. Both relative and absolute amounts of the six elements differed between the two species of fish, and, more so, between the two tissues. The mussel contained higher amounts of the elements than the fish. The pattern of the elements was also very different in the mussel. Differences and similarities among the various types of samples from the eight locations were evaluated by principal component analysis. Correlation between the six elements was also tested by this method. A concentration gradient away from the source of pollution was only found for arsenic in the saithe tissues, while the only gradient detected in flounder was for mercury in the liver tissue. In mussels the gradient for arsenic was marginal, while gradients were detected in varying degrees for the other elements. Cadmium did not correlate with the other elements in mussels. The mussel was found to be a much better sentinel organism for these elements, except arsenic, than the two fish species.

The effect of copper-treated net pens on farmed salmon (Salmo salar) and other marine organisms and sediments

Samples of Atlantic salmon (Salmo salar), saithe (Pollacius virens), blue mussel (Mytilus edulis), brown seaweed (Ascophyllum nodosum) and sediment were collected from six different fish farms. Five of the farms used net pens treated with copper-containing coatings, whereas one farm did not use copper-containing coating (this was used as a reference location). Samples of muscle, liver and gills of Atlantic salmon and saithe, blue mussel and brown seaweed were freeze dried, homogenised, wet digested and analysed for copper by flame atomic absorption spectrometry. The results showed no significant differences in copper concentrations among the samples from the different locations. The copper contents of some of the samples appeared to be in the upper part of the normal concentration range. From a nutritional point of view, the use of copper-coatings on net pens did not affect the quality of the seafood products either within, or around the net pen.

Ascorbate-2-sulfate as a dietary vitamin C source for Atlantic salmon (Salmo salar): 2. Effects of dietary levels and immunization on the metabolism of trace elements

Atlantic salmon fingerlings were fed a vitamin C deficient diet for four months. The fish were then provided a dry, practical fishmeal based diet supplemented with 0, 500 or 5000 mg vitamin C/kg as L-ascorbic acid or equivalent amounts of ascorbate-2-sulfate. After six weeks on these diets ten fish in each group were injected with a soluble antigen (NIP11-LPH). Six weeks thereafter blood, liver, kidney, spleen and vertebrae were examined for trace elements. The livers were also analysed for metallothionein.The vitamin C deficient fish were anemic despite the significantly elevated iron concentrations in the liver. Vitamin C had no positive effect in lowering tissue levels of cadmium. The highest level of dietary vitamin C given as ascorbic acid reduced the liver selenium concentrations. In response to antigen injection, the fish in all groups showed increased levels of hepatic metallothionein, copper, zinc and cadmium, while hepatic selenium and iron levels were less affected. The elemental composition in other organs was affected by the antigen injection to a minor extent.

A comparison of growth rate and trace element accumulation in Atlantic salmon (Salmo salar) fry fed four different commerical diets

Abstract “Swim up” Atlantic salmon ( Salmo salar ) fry were fed four commercial start diets for 4 weeks. Calcium, iron, copper, zinc, selenium as well as ascorbic acid, water, protein, fat and ash contents were determined in the feeds and the elements were determined in the fry. There were significant correlations between the levels of calcium, iron and zinc in the diets and in the whole fry. Significant positive correlations were also found between the weight of the developing fry and the concentrations of carcass zinc and selenium, thus showing an accumulation of these elements during early growth.

An indirect determination of iodine using HgIn complexes and cold vapour atomic absorption determination of mercury

Abstract The formation of HgI n ,-complexes ( n = 1,2,3,4) at high acidity causing suppression in the mercury absorbance may be used for the indirect determination of iodine by cold vapour atomic absorption spectrometry (AAS). The stability of the complexes is increased by an increase in the acidity and a decrease in the amounts of tin (II) chloride as the reductant in the reaction solution. The characteristic concentration (for 1 % absorption) and the detection limit were 1.1 × 10 −8 and 5 × 10 −8 g iodine, respectively. The effects of some noble metals and other halogens have been studied. The decomposition procedure applied was found to be critical for the recovery. Potassium hydroxide fusion gave the best recovery and accuracy. The method was applied to NBS oyster tissue and citrus leaves, and to cod liver oil.

A comparative study of the determination of phosphorus by electrothermal atomic absorption spectrometry and solution spectrophotometry

Abstract Graphite-furnace atomic absorption spectrometry (a.a.s.) and a spectrophotometric AutoAnalyzer method for phosphorus based on molybdovanadophosphate formation are compared. Only slight improvements in accuracy and reproducibility were obtained when SiC- or ZrC-coated graphite tubes replaced uncoated tubes. Perchloric acid enhanced the phosphorus signal in a.a.s. The digestion system was found to be critical for the AutoAnalyzer method. Digetion with nitric/perchloric acids gave higher recoveries than a micro-Kjeldahl digestion for most of the biological samples studied. Better accuracy was obtained by the a.a.s. method, whereas the AutoAnalyzer method was more reproducible. The methods were applied to NBS Oyster Tissue and Spinach, and fish samples.