Influence of Camelina Oil-Containing Diets on the Atlantic Cod Antiviral Immune Transcriptome and Elovl Family Transcript Expression

Aquaculture feeds for carnivorous fish such as cod currently contain fish oil (FO) and fish meal, non-sustainable ingredients largely harvested from wild fish stocks.  The oilseed Camelina sativa is an alternative source of oil and protein for aquafeeds.  However, research is needed to study the impact of camelina oil (CO) on biological processes such as growth and immune responses.  A 20K microarray experiment evaluated the spleen transcriptome response to intraperitoneal injection with the viral mimic pIC (versus saline-injected control) in cod fed test diets (0%, 40% or 80% of FO replaced with CO) for 11 weeks.  While there were large lists of pIC-responsive genes at 24 hours post-injection (24 HPI) within each diet group, a comparison of 24 HPI pIC samples between diets found no differentially expressed genes.  QPCR for 5 anti-viral biomarkers at 6 and 24 HPI likewise showed no differences in pIC response between diets.  Since Elovl genes encode enzymes involved in fatty acid biosynthesis, they may play roles in cod responses to diets containing CO (rich in shorter chain PUFAs ALA and LA).  We characterized 10 members of the cod Elovl gene family, and studied constitutive expression of these genes in 15 tissues.  QPCR showed that, in liver, Elovl5 and Fadsd6 were significantly up-regulated in cod fed a diet with solvent-extracted fish meal and 100% CO replacement of FO compared to FO diet after a 13-week trial.  Growth data and results of multivariate statistical analyses comparing Elovl5 and Fadsd6 expression and fatty acid profiles will be presented.