North Atlantic fish oils, such as mackerel oil and herring oil, contain lower levels of EPA and DHA compared to South American fish oils like anchovy and sardine oils. However, they are very rich in marine long-chain monounsaturated fatty acids, especially cetoleic acid (22:1 n-11). Cetoleic acid can make up around 17-25% of the total fatty acids in a North Atlantic fish oil, compared to around 1% in a typical South American fish oil.
In previous studies, we have shown that cetoleic acid can stimulate the synthesis of EPA and DHA in liver cells from both humans and salmon. Furthermore, we found that salmon smolts fed a herring oil-based diet rich in cetoleic acid had higher apparent retentions of EPA and DHA in the whole body, compared to salmon fed a sardine oil-based diet with low cetoleic acid content.
A feeding trial with Atlantic salmon in sea cages , 100 fish per cage, was conducted to investigate how cetoleic acid rich diets influence the growth, feed utilization, whole body retentions of omega-3 fatty acids and visceral adipose tissue depots . Atlantic salmon of approximately 1 kg were fed three experimental diets with increasing levels of herring oil in triplicate cages until the fish reached 4 kg.
The inclusion level of cetoleic acid in the diets did not affect the growth rate or feed utilization, but improved the retention of omega-3 fatty acids in whole body, affected the gene expression of several inflammatory markers and lipogenic enzymes, reduced condition factor, and improved visceral fat score and slaughter yield.