Lerøy (Norway)

Blue mussel (Mytilus edulis) could be a promising marine protein source in fish feeds and is of great interest since it can be cultivated along the Norwegian coastline. However, the use of blue mussels in feeds is dependent on developing suitable preservation and processing methods to produce a feed grade raw material. The present studies were conducted to investigate whether blue mussel silage could be used in the feed for Atlantic salmon post-smolt. Two feeding experiments were conducted using the same reference diet with FM inclusion of 25%, giving a mix of ∼59–63% plant-based ingredients vs ∼34–36% marine ingredients to simulate a standard grower feed for salmon post-smolts in SW. In experiment 1, fish were fed diets containing three different inclusion levels of blue mussel silage (BMS 3, 7, and 11%), a diet containing blue mussel meal (BMM) (12%) as well as the reference feed. In this experiment, the fish that were fed a diet containing BMS had a decline in both weight gain and condition factor when compared to the fish given the reference and BMM. The daily feed intake was similar in all groups, but the feed conversion ratio (FCR) increased in the fish fed BMS. The inclusion of BMS and BMM did not affect the digestibility of nutrients, but reduced retention of whole-body lipid and protein retention was observed. Salmon given BMS in the diet also had lower iron (Fe) concentrations in liver and whole body, indicating lower Fe uptake, irrespective of inclusion level. These findings were followed up in a second feeding experiment aiming to investigate whether different processing methods of blue mussel silage could influence the bioavailability of iron, as well as feed utilization and growth. The reference feed was formulated similar to the feed in exp. 1. Additionally, fish were fed diets containing BMM (9%) and the same batch of BMS (9%) used in exp. 1 as well as two diets containing new productions of BMS (9%) using either a lower acid level or only formic acid at the same level. In experiment 2, no differences were seen in weight gain, feed intake, FCR, nutrient retention or body composition between fish given BMS and reference diet. The lower Fe status observed in experiment 1 was not seen in the second study. In both experiments, there were no differences in fish welfare indicators between the group of fish fed with BMS, BMM and the reference group.The present results show that blue mussel silage can be used in the diet for Atlantic salmon, however, the different processing and preservation methods to produce BMS influence the nutritional properties and consequently growth performance and feed utilization of Atlantic salmon post-smolts.

Light cues vary along the axis of periodicity, intensity and spectrum and perception of light is dependent on the photoreceptive capacity encoded within the genome and the opsins expressed. A global approach was taken to analyze the photoreceptive capacity and the effect of differing light conditions on a developing teleost prior to first feeding. The transcriptomes of embryos and alevins of Atlantic salmon (Salmo salar) exposed to different light conditions were analyzed, including a developmental series and a circadian profile. The results showed that genes mediating nonvisual photoreception are present prior to hatching when the retina is poorly differentiated. The clock genes were expressed early, but the circadian profile showed that only two clock genes were significantly cycling before first feeding. Few genes were differentially expressed between day and night within a light condition; however, many genes were significantly different between light conditions, indicating that light environment has an impact on the transcriptome during early development. Comparing the transcriptome data from constant conditions to periodicity of white light or different colors revealed overrepresentation of genes related to photoreception, eye development, muscle contraction, degradation of metabolites and cell cycle among others, and in constant light, several clock genes were upregulated. In constant white light and periodicity of green light, genes associated with DNA replication, chromatin remodeling, cell division and DNA repair were downregulated. The study implies a direct influence of light conditions on the transcriptome profile at early developmental stages, by a complex photoreceptive system where few clock genes are cycling.

ABSTRACTThe concept of a holobiont, a host organism and its associated microbial communities, encapsulates the vital role the microbiome plays in the normal functioning of its host. Parasitic infections can disrupt this relationship, leading to dysbiosis. However, it is increasingly recognized that multicellular parasites are themselves holobionts. Intestinal parasites share space with the host gut microbiome, creating a system of nested microbiomes within the primary host. However, how the parasite, as a holobiont, interacts with the host holobiont remains unclear, as do the consequences of these interactions for host health. Here, we used 16S amplicon and shotgun metagenomics sequencing to characterize the microbiome of the intestinal cestode Eubothrium and its effect on the gut microbiome of its primary host, Atlantic salmon. Our results indicate that cestode infection is associated with salmon gut dysbiosis by acting as a selective force benefiting putative pathogens and potentially introducing novel bacterial species to the host. Our results suggest that parasitic cestodes may themselves be holobionts nested within the microbial community of their holobiont host, emphasizing the importance of also considering microbes associated with parasites when studying intestinal parasitic infections.

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Two duplicate groups of individually tagged lumpfish (mean initial weight: 21.5 ± 3.2 g) were fed either a commercially available lumpfish feed or feed blocks for a period of 123 days. The aim was to evaluate and compare the effects of these feed types on growth, cataract development and histopathology in lumpfish. There were significant differences in growth rates between the groups with fish fed pelleted feed having the highest growth rates. The development of cataracts was significantly different with fish fed pelleted feed having a cataract prevalence of 87% at the end of the study period whilst fish fed with feed blocks had 10% prevalence. The results of the histological examination undertaken in this study showed overall small differences between the two dietary treatments. In some individuals in groups receiving both diets, there was mild to moderate expansion of the lamina propria with tissue most likely to represent fibrous tissue with scattered leucocytes. Overall, the findings of the present study show that lumpfish will readily graze from feed blocks and although growth is lower the prevalence of cataract is greatly reduced using feed blocks.

In this paper, a new approach to a nonlinear dq model is proposed for transient simulations of a salient-pole wound-rotor synchronous machine with dampers. Despite the nonlinearity between the flux linkage and the current, the comparison with finite element simulations shows that the new model is reliable for saturated transient state of the machine. This method allows to obtain far more accurate results than a classical nonlinear dq model, which assumes the equality between the mutual inductances. This model contains many improvements compared to most nonlinear dq models. The first one consists of considering each mutual inductance individually. The saturation of every inductance and its leakage part are evaluated separately. Furthermore, the calculation method of the mutual inductance between the stator circuits and the damper circuits is presented. Finally, the cross magnetization is introduced. This makes the proposed model closer to reality than most of traditional models.

Introduction: Loss-of function mutations in HERG potassium channels in Long QT2 syndrome are associated with sudden cardiac death triggered by sympathetic surge. In various models of cardiac disease changes in calcium (Ca) homeostasis, associated with upregulated plasmalemmal Na/Ca exchanger (NCX) and/or hyperactive ryanodine receptors (RyRs), have been linked to increased risk of arrhythmia. Methods and Results: The aims of this study were to investigate possible changes in Ca homeostasis in cardiomyocytes derived from from the hearts of LQT2 rabbits and to determine whether similar changes contribute to the triggering of early afterdepolarizations (EADs) characteristic of LQT2 myocytes under β-adrenergic stimulation. Parameters of Ca handling were measured in ventricular myocytes enzymatically isolated from LQT2 and littermate control hearts using confocal Ca imaging and whole cell patch clamp. Ca imaging revealed no changes in amplitude of Ca transients in intact myocytes and sarcoplasmic reticulum (SR) Ca content assessed by measuring amplitude of transients evoked by rapid application of caffeine. A two-fold increase in rate of decay of caffeine-induced Ca transients in LQT2 myocytes vs. controls indicated increased NCX activity. Experiments in saponin-permeabilized cells using a SR-entrapped low-affinity Ca indicator revealed ~2-fold increase in RyR-mediated SR Ca leak in LQT2 myocytes in comparison with controls. In contrast to controls, current-clamped LQT2 myocytes exposed to β-adrenergic agonist isoproterenol exhibited prolonged plateau of action potentials (AP) at -10 - 0 mV accompanied by aberrant Ca releases and phase 3 EADs. Importantly, complete exhaustion of SR [Ca] by incubation of LQT2 cells with SERCA inhibitor thapsigargin or 10 mM caffeine, shortened APD and completely abolished EADs. Conclusion: Functional changes in RyR and NCX underlie preserved systolic Ca transients in LQT2 myocytes under basal conditions and may contribute to stress-induced arrhythmia by maintaining the plateau of AP at voltages ideal for reactivation of plasmalemmal Ca channels and generation of EADs.