In the current situation with limited supply of fish oil, it is impossible to maintain or increase the production of Atlantic salmon while maintaining current involvement of fish oil. This has a number of consequences, of which the most obvious is a reduced content of omega -3 fatty acids EPA and DHA in the diet. Reduced use of fish oil also means replacement with other fat sources and consequences are major changes in fatty acid composition in the feed. There is a need for more knowledge about how these changes affect fish health, including the requirement for saturated fat, the consequences of a sharp reduction in saturated fats on fish health, and to determine the upper limit for digestibility. In addition, one must look at the importance of omega6 / omega3 ratio or total omega6 level in salmon, where the optimal ratio of omega -3 and omega -6 must be determined simultaneously with the minimum requirements and upper tolerance limit. In particular, there is a large uncertainty related to how changes in fatty acid composition may affect salmon resistance to viral diseases. There is evidence that fatty acid composition in feed influences infection and immune response in Atlantic salmon, but knowledge of what is optimal fatty acid composition for protection against viral infections is lacking. Many in vitro experiments have shown effects of omega -3 and omega -6 both in immune responses and inflammation.
- Increase the knowledge on how fatty acid composition in the diet affects the inflammatory and immune responses in head kidney cells/macrophages, when these are stimulated with LPS (trigger inflammation) and with various viruses.
- Examine if the fatty acid composition in the diet affects resistance to virus disease (PD), by challenging selected feeding groups of salmon in an artificial infection experiment.