Fish from aquaculture is an important source for n-3 fatty acids (FAs), EPA and DHA, for humans. Traditionally, fish oils (FOs) are used in salmonid feeds. FO's are becoming a limited resource, and aquaculture is clearly not capable of developing in a sustainable manner without new solutions.
FO is replaced with plant oils in fish diets, causing reduced level of EPA and DHA in fish muscle. It is important to maximise the innate ability of fish to synthesise the long chain n-3 FAs EPA and DHA from 18:3n-3 in order to preserve the lipid quality of the fish as human food and for sustainable utilization of feed resources.
The unique aspect of this project is to combine genetic information of the fish, with a careful selection and combination of lipid sources, to improve capacity for EPA and DHA production in Atlantic salmon, making this species a net producer of the healthy n-3 FAs.
Selection of oils and fish will be based on genetic information regarding ability to perform the conversion from ALA to EPA and DHA. We will clone and genetically and functionally characterise the delta-5 and delta-6 desaturases in Atlantic salmon and rainbow trout. Based on these data we will screen for the chosen desaturase gene in salmon families from a commercial breeding program, and select families with high and low expression of the selected desaturase, for the feeding experiment. The same families will be used for QTL-mapping.
Simultaneously we will supplement different ratios of FAs in the culture media of hepatocytes, to find the ratios of FAs that give the highest stimulation of desaturase gene expression and highest output of n-3 HUFA production.
Based on these results we will select oils and design oil mixes to be tested in the feeding trial, to study deposition of n-3 FAs. Fish from the feeding trial will be used for analyses of genetic predisposition in the ability to convert ALA to EPA and DHA, and to study effects on fish health and welfare.