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Post-smolt Atlantic Salmon (post-smolt + atlantic_salmon)
Selected AbstractsDoes the capacity for energy utilization affect the survival of post-smolt Atlantic salmon, Salmo salar L., during natural outbreaks of infectious pancreatic necrosis?JOURNAL OF FISH DISEASES, Issue 7 2007K-A Rørvik Abstract If osmotic stress and reduced seawater tolerance are predisposing factors for infectious pancreatic necrosis (IPN) outbreaks in farmed Atlantic salmon, increased survival by enhancing access to energy would be expected. The aim of the present study was, therefore, to increase energy access in 1-year old Atlantic salmon after sea transfer by increasing the level of dietary fat, by exchanging some of the dietary oil with more easily oxidized medium chain triacylglycerols, or by dietary supplementation of potentially energy enhancing additives such as clofibrate and tetradecylthioacetic acid (TTA). A natural outbreak of IPN occurred 8 weeks after sea transfer, and a significant dietary effect explaining 76% of the variation in mortality was observed. Relative percentage survival for the fish fed TTA in sea water was 70% when compared with the unsupplemented control, reducing mortality from 7.8 to 2.3%. Muscle fat content and plasma chloride were related to IPN mortality, suggesting that reduced hypoosmoregulatory capacity might be a predisposing factor to the onset of an IPN outbreak. Based on the observation of a threefold increase in white muscle mitochondrial fatty acid oxidizing activity by TTA, it is suggested that TTA has resulted in a re-allocation of dietary fatty acids from storage to energy producing oxidation. [source] Evaluation of stress- and immune-response biomarkers in Atlantic salmon, Salmo salar L., fed different levels of genetically modified maize (Bt maize), compared with its near-isogenic parental line and a commercial suprex maizeJOURNAL OF FISH DISEASES, Issue 4 2007A Sagstad Abstract The present study was designed to evaluate if genetically modified (GM) maize (Bt maize, event MON810) compared with the near-isogenic non-modified (nGM) maize variety, added as a starch source at low or high inclusions, affected fish health of post-smolt Atlantic salmon, Salmo salar L. To evaluate the health impact, selected stress- and immune-response biomarkers were quantified at the gene transcript (mRNA) level, and some also at the protein level. The diets with low or high inclusions of GM maize, and its near-isogenic nGM parental line, were compared to a control diet containing GM-free suprex maize (reference diet) as the only starch source. Total superoxide dismutase (SOD) activity in liver and distal intestine was significantly higher in fish fed GM maize compared with fish fed nGM maize and with the reference diet group. Fish fed GM maize showed significantly lower catalase (CAT) activity in liver compared with fish fed nGM maize and to the reference diet group. In contrast, CAT activity in distal intestine was significantly higher for fish fed GM maize compared with fish fed reference diet. Protein level of heat shock protein 70 (HSP70) in liver was significantly higher in fish fed GM maize compared with fish fed the reference diet. No diet-related differences were found in normalized gene expression of SOD, CAT or HSP70 in liver or distal intestine. Normalized gene expression of interleukin-1 beta in spleen and head-kidney did not vary significantly between diet groups. Interestingly, fish fed high GM maize showed a significantly larger proportion of plasma granulocytes, a significantly larger sum of plasma granulocyte and monocyte proportions, but a significantly smaller proportion of plasma lymphocytes, compared with fish fed high nGM maize. In conclusion, Atlantic salmon fed GM maize showed some small changes in stress protein levels and activities, but none of these changes were comparable to the normalized gene expression levels analysed for these stress proteins. GM maize seemed to induce significant changes in white blood cell populations which are associated with an immune response. [source] Reduced sexual maturation in male post-smolt 1+ Atlantic salmon (Salmo salar L.) by dietary tetradecylthioacetic acidAQUACULTURE RESEARCH, Issue 5 2009Henriette Alne Abstract In the present study, the possible effect of dietary treatment on early sexual maturation in post-smolt Atlantic salmon, without any negative effect regarding growth, was investigated. The experiment was performed using 4400 individually marked (Pit tag) 1+ salmon, fed either a control diet or a diet supplemented with 0.5% tetradecylthioacetic acid (TTA) in duplicates for 3, 6 or 12 weeks after sea transfer. Compared with the control, dietary supplementation of TTA resulted in a threefold reduction in incidence of sexual mature males (0.6% vs. 1.8%). A curve-linear relationship between relative reduction in maturation and weeks of feeding TTA was found, indicating that the effect is most marked as a result of the first weeks of feeding and then levelling off. No negative dietary impact on growth was observed. As the level of fat in the muscle was reduced by dietary TTA, it seems that post-smolt supplemented dietary TTA do not accumulate high enough energy stores to start the maturation process, whereas the energy-enhancing effect of TTA due to increased fatty acid oxidation capacity may maintain the growth potential. Compared with immature salmon, sexually maturing fish revealed increased spring growth before the onset of maturation. [source] Nutritive value of partially dehulled and extruded sunflower meal for post-smolt Atlantic salmon (Salmo salar L.) in sea waterAQUACULTURE RESEARCH, Issue 13 2006Navneet Gill Abstract This study determined the digestibility of protein in partially dehulled sunflower meal (SFM) and then, as the main goal, the nutritive value of high-temperature extruded (,149°C) partially dehulled SFM (SFMEX) for post-smolt Atlantic salmon Salmo salar in sea water. The digestibility study was conducted using the settling column approach (,Guelph system') for faeces collection as described by Hajen, Higgs, Beames and Dosanjh. In the nutritive value study, triplicate groups of 50 salmon (mean weight ,116 g) in 4000-L outdoor fibreglass tanks supplied with 25,40 L min,1, filtered, oxygenated (dissolved oxygen, 7.0,8.5 mg L,1), 11,12°C sea water (salinity, 29,31 g L,1), were fed twice daily to satiation one of five steam-pelleted dry diets that contained 422 g of digestible protein (DP) kg,1 and ,16.4 MJ of digestible energy (DE) kg,1 on a dry weight basis for 84 days. Low-temperature-dried anchovy meal (LT-AM) comprised 68.2% of the basal diet protein whereas in four test diets, SFMEX progressively replaced up to 33.0% of the DP provided by LT-AM in the basal diet (SFMEX,271 g kg,1 of dry matter). Sunflower meal had 87.9% DP. Diet treatment did not significantly affect specific growth rate (1.39,1.45% day,1), feed efficiency (1.19,1.26), percentage of dietary protein retained (45.8,47.5), gross energy utilization (46.5,49.4%), per cent survival (96.0,99.3) or terminal whole body and muscle proximate compositions. We conclude that SFMEX can comprise ,271 g kg,1 of the dry diet or ,22.7% of the digestible dietary protein of post-smolt Atlantic salmon in seawater without any adverse effects on their performance. [source] | ||||||||||