Robust salmon skin - genetics, vaccination and nutrition

Farmed salmon are exposed to mechanical stresses and pathogens that result in wounds on the fish's skin. Damage to the fish's exterior presents physiological challenges and reduced welfare, as well as loss of reputation and poorer economy for the industry. The Robust Skin project was initiated to see if the skin health of farmed Atlantic salmon could be enhanced through selective breeding, development of a more effective vaccine and optimization of feed composition. In contrast to terrestrial animals, the fish's skin consists of living cells that are important for osmoregulation and resistance to pathogenic microorganisms. Analyzes of salmon after mechanical de-lousing show that the treatment results in damage to the surface epithelium, ranging from small microscopic tears to larger visible areas with shell loss. In the project, we have shown that effective wound healing in salmon is affected by genetics and the results are now being followed up in a new project. De-lousing also alters the skin microbiome, which can lead to the growth of pathogenic bacteria if they are present in the environment. Genetic analyzes of different Moritella strains from salmon show changes over time, but not coincident strains in salmon and lumpfish. Moritella infection is therefore unlikely between the species. Infection experiments with the winter ulcer bacterium Moritella viscosa, show that genetics has an impact on survival. This is now being followed up in a new project. Similar infection tests with vaccine and functional feed have also shown good results, with reduced mortality and ulceration. In a recent challenge trial, where the best genetics, vaccine and functional feed were compared with standard products, ulceration was halved and loss reduced from 70% and down to 10%. The project has led to the development of new products and projects and shown that the combination of genetics, vaccine and diet can contribute significantly to improved fish welfare.

Prosjektet har gitt industripartnerene muligheten til å forske på laksens skinnhelse innenfor de respektive produktområdene, men også se om det finnes samspillseffekter. Uten prosjektfinansiering er denne typen samarbeid vanskelig å få gjennomført. Industripartnerene har med prosjektet etablert metoder, prosesser og produkter som kommer oppdretteren til gode, gitt att oppdretteren tar kunnskapen i bruk. På lengre sikt kan prosjektresultatene gi en mer robust laks som følge av kontinuerlig seleksjon på skinnhelse og utvikling av oppdaterte vaksiner og fôr basert på dette prosjektet. Økt fokus på skinnhelse og oppdrett av laks hvor aktørene tar hensyn til fisken biologi er viktig for utnyttelse av prosjektresultatene.

The project aims to improve skin health of Atlantic salmon by reducing wound related problems. Farmed salmon endure a challenging environment where handling may damage the epithelial surface and increase accessibility for pathogenic microbes, potentially leading to infections. A small study of epithelial integrity and the microbial community has been included in the project to assess the effects of delousing, as recent reports implies adverse effects to the outer epithelial surfaces. The importance of skin microbiome composition and epithelial health is important in net pens and even more so in closed recirculation systems. The results from this baseline study and the established protocols will provide important knowledge on how a common treatment affects microbes and salmon skin. The knowledge about wound healing in A. salmon is scarce. Genetic background profoundly affects wound healing efficiency in mammals and the project aims to select salmon with rapid healing of epithelial surfaces to minimize the risk of skin infections. An intact outer epithelial surface has been shown and even minuscule wounds facilitates M. viscosa infections and development of winter ulcers in A. salmon. The main objectives of the project is to genetically select salmon with increased resistance to M. viscosa. Another objective is to select salmon with improved protective immune responses to M. viscosa vaccines and to further develop and improve the formulation. Functional diets is important in salmon farming and has been shown to improve resistance against pathogens. In this project we seek to address wound healing and further develop diet composition to improve skin health, taking the genetic background into the study. This novel combination of approaches improves wound related problems and increases the possibilities for improving fish health and welfare as well as reducing loss and costs.