U Nordgarden

Publications (7)10.4 Total impact

• Article: Effects of vegetable feed ingredients on bone health in Atlantic salmon

  P. G. Fjelldal, U. Nordgarden, A. Wargelius, G. L. Taranger, R. Waagbø, R. E. Olsen
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  ABSTRACT: The aim of the present study was to examine if dietary inclusion of vegetable lipids (VL) and proteins (VP) influenced markers of bone health in Atlantic salmon. Triplicate groups were fed one of four different diets; 100% fish protein (FP) and fish lipids (FL) (FPFL), 80% VP and 35% VL (80VP35VL), 40% VP and 70% VL (40VP70VL), or 80% VP and 70% VL (80VP70VL) for 12 months on-growth in sea water. Fish were analyzed for vertebral bone mineralization (mineral content, as % of bone dry weight), vertebral deformities (radiology), vertebral bone mRNA expression of factors involved in mineralization (bone gla protein, bgp) and growth regulation (igf-I and growth hormone receptor), as well as plasma vitamin D metabolites. The fish grew from 0.35 to 4 kg during the experimental period. At the end of the experiment, significantly lower prevalence of fish with one or more deformed vertebrae was observed in the 80VP70VL group (11%) compared to the other groups (33–43%). There was a significant higher relative expression of igf-I mRNA in vertebral bone of fish fed the 80VP70VL diet compared to control fish (FPFL), while the other genes studied were unaffected. Elevated plasma 25-hydroxyvitamin D3 recorded in the marine feed group is discussed as a predictor for later development of bone deformities. In conclusion, the present study shows that high inclusion levels of vegetable lipids and proteins may have a positive effect on bone health in Atlantic salmon postsmolts.
  Journal of Applied Ichthyology 04/2010; 26(2):327 - 333. · 0.87 Impact Factor
• Article: Collagen type XI alpha1 may be involved in the structural plasticity of the vertebral column in Atlantic salmon (Salmo salar L.).

  A Wargelius, P G Fjelldal, U Nordgarden, A Grini, C Krossøy, S Grotmol, G K Totland, T Hansen
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  ABSTRACT: Atlantic salmon (Salmo salar L.) vertebral bone displays plasticity in structure, osteoid secretion and mineralization in response to photoperiod. Other properties of the vertebral bone, such as mineral content and mechanical strength, are also associated with common malformations in farmed Atlantic salmon. The biological mechanisms that underlie these changes in bone physiology are unknown, and in order to elucidate which factors might be involved in this process, microarray assays were performed on vertebral bone of Atlantic salmon reared under natural or continuous light. Eight genes were upregulated in response to continuous light treatment, whereas only one of them was upregulated in a duplicate experiment. The transcriptionally regulated gene was predicted to code for collagen type XI alpha1, a protein known to be involved in controlling the diameter of fibrillar collagens in mammals. Furthermore, the gene was highly expressed in the vertebrae, where spatial expression was found in trabecular and compact bone osteoblasts and in the chordoblasts of the notochordal sheath. When we measured the expression level of the gene in the tissue compartments of the vertebrae, the collagen turned out to be 150 and 25 times more highly expressed in the notochord and compact bone respectively, relative to the expression in the trabecular bone. Gene expression was induced in response to continuous light, and reduced in compressed vertebrae. The downregulation in compressed vertebrae was due to reduced expression in the compact bone, while expression in the trabecular bone and the notochord was unaffected. These data support the hypothesis that this gene codes for a presumptive collagen type XI alpha1, which may be involved in the regulatory pathway leading to structural adaptation of the vertebral architecture.
  Journal of Experimental Biology 04/2010; 213(Pt 7):1207-16. · 3.00 Impact Factor
• Article: Seasonally changing metabolism in Atlantic salmon (Salmo salar L.) II –β‐oxidation capacity and fatty acid composition in muscle tissues and plasma lipoproteins

  U. Nordgarden, B.E. Torstensen, L. Frøyland, T. Hansen, G.-I. Hemre
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  ABSTRACT: With the aim of elucidating seasonally changing lipid metabolism in immature Atlantic salmon (Salmo salar L.) in sea water, one group was reared under simulated natural light, while one group was reared under continuous light. Fatty acid profile in plasma lipoproteins did not vary during the experiment, while β-oxidation capacity increased during spring, concurrent with decreasing temperatures. Simultaneously, the relative level of monounsaturated fatty acids (MUFA) in muscle tissue decreased (42–36%). Muscle levels of saturated fatty acids were low during early spring (19%), but then increased slowly, and muscle levels of polyunsaturated fatty acids increased during spring (from 36% to 39%). It is suggested that increased spring growth and the concomitant energy demand was met by increased lipid oxidation, where MUFA were preferred as energy substrate.
  Aquaculture Nutrition 09/2003; 9(5):295 - 303. · 2.18 Impact Factor
• Article: Seasonally changing metabolism in Atlantic salmon (Salmo salar L.) I – Growth and feed conversion ratio

  U. Nordgarden, F. Oppedal, G.L. Taranger, G.-I. Hemre, T. Hansen
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  ABSTRACT: 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.
  Aquaculture Nutrition 09/2003; 9(5):287 - 293. · 2.18 Impact Factor
• Article: Seasonal changes in selected muscle quality parameters in Atlantic salmon (Salmo salar L.) reared under natural and continuous light

  U. Nordgarden, R. Ørnsrud, T. Hansen, G.-I. Hemre
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  ABSTRACT: 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.
  Aquaculture Nutrition 05/2003; 9(3):161 - 168. · 2.18 Impact Factor
• Article: Endocrine growth regulation of adult Atlantic salmon in seawater: The effects of light regime on plasma growth hormone, insulin-like growth factor-I, and insulin levels

  U. Nordgarden, T. Hansen, G. I. Hemre, A. Sundby, B. T. Bjornsson
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  ABSTRACT: Plasma growth hormone (GH), insulin-like growth factor-I (IGF-I), and insulin were measured in two groups of Salmo salar L. during a one-year study. The fish were reared under either a simulated natural photoperiod (SNP) from January to December or a regime of continuous light from January to June, followed by SNP until December (LL/SNP). Plasma GH levels during spring were low, and lower in the LL/SNP fish (< 0.9 ng ml(-1)) than in the SNP fish (> 1.9 ng ml(-1)), although the LL/SNP grew better (0.8% per day) than the SNP fish (0.5% per day). Plasma IGF-I levels increased transiently from January (64.7 ng ml(-1)) to maximum in late September in the LUSNP (85.8 ng ml(-1)) and in November in the SNP group (87.3 ng ml(-1)). The ratio GH:IGF-I was lower in the LL/SNP group during spring when this group grew better than the SNP group. (c) 2005 Elsevier B.V. All rights reserved.
  Aquaculture. 250(3-4):862-871.
• Article: Developmental stage of Atlantic salmon parr regulates pituitary GH secretion and parr-smolt transformation

  U. Nordgarden, B. T. Bjornsson, T. Hansen
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  ABSTRACT: Atlantic salmon respond to increased photoperiod by elevation of plasma growth hormone (GH) levels during the period leading up to parr-smolt transformation, both under natural and farming conditions. The aim of the present study was to elucidate the ontogeny of this response, by exposing juvenile Atlantic salmon to increased daylength at different stages of development. Salmon fry were reared on 12 It light:12 h dark from first feeding and thereafter exposed to continuous light from a mean fork length of 5 cm (LL5) or 8 cm (LL8). Plasma GH increased in smolting individuals in the LL8 group, whereas in the LL5 group as well as in Parr of the LL8 group, plasma GH levels remained low. Growth rate in length increased significantly in both groups in response to increase in daylength. Plasma IGF-I varied to a lesser degree, although in late July, the LL5 IGF-I levels exceeded those of the LLS IGF-I levels. In the LL8 group, 33% of the fish smoltified 6 weeks after onset of continuous light, whereas all the fish in the LL5 group failed to smolt. At termination of the experiment, the incidence of precocious maturing males in the LL5 and LL8 group were 38% and 62%, respectively. In conclusion, based on the lack of a GH response in fish smaller than 8 cm, it is hypothesized that the development of a functional light-pituitary axis leading to an increase in plasma GH levels, sets the threshold developmental stage for successful parr-smolt transformation of Atlantic salmon. (c) 2007 Elsevier B.V. All rights reserved.
  Aquaculture. 264(1-4):441-448.