Publisher: Nofima AS
Number of pages: 32
International Standard Numbers:
Open Access: green
The objective of the project was to increased knowledge on how genetic background, smoltification and feed composition affect salmon’s innate capacity to produce and dispose of EPA and DHA. Salmon that followed a postponed smoltification regime showed better capacity to synthesize EPA and DHA, than salmon going through a normal smoltification regime. Salmon smoltified at a later stage also showed higher level of DHA in the fillet than salmon smoltified at a normal time point. Gene expression of all desaturases were down-regulated by light treatment, while transfer to saltwater upregulated 6fad_b and 6fad_c. Light seems to inhibit the enzyme activity of 5 desaturase and stimulate activity of 6 desaturase. Salmon from most of the High-desaturase groups showed in February higher capacity to synthesize EPA + DHA than Low-desaturase groups. These results show that families selected for high gene expression of 6 desaturase (6fad_b), also have better capacity to synthesize EPA + DHA. Groups fed 90 % RO showed higher gene expression level of all desaturases, than the group fed 25 % RO. This may be caused by an inhibitory effect of dietary DHA on gene expression of desaturases.