Are we what we eat? Changes to the feed fatty acid composition of farmed salmon and its effects through the food chain

Abstract

‘Are we what we eat?’ Yes and no. Although dietary fat affects body fat, there are many modifying mechanisms. In Atlantic salmon, there is a high level of retention of the n-3 fatty acid (FA) docosahexaenoic acid (DHA, 22:6n-3) relative to the dietary content, whereas saturated FAs never seem to increase above a specified level, which is probably an adaptation to low and fluctuating body temperature. Net production of eicosapentaenoic acid (EPA, 20:5n-3) and especially DHA occurs in salmon when dietary levels are low; however, this synthesis is not sufficient to maintain EPA and DHA at similar tissue levels to those of a traditional fish oil-fed farmed salmon. The commercial diets of farmed salmon have changed over the past 15 years towards a more plant-based diet owing to the limited availability of the marine ingredients fish meal and fish oil, resulting in decreased EPA and DHA and increased n-6 FAs. Salmon is part of the human diet, leading to the question ‘Are we what the salmon eats?’ Dietary intervention studies using salmon have shown positive effects on FA profiles and health biomarkers in humans; however, most of these studies used salmon that were fed high levels of marine ingredients. Only a few human intervention studies and mouse trials have explored the effects of the changing feed composition of farmed salmon. In conclusion, when evaluating feed ingredients for farmed fish, effects throughout the food chain on fish health, fillet composition and human health need to be considered.

Application of polychaetes in (de)coupled integrated aquaculture: production of a high-quality marine resource

“…Amino acids are the building blocks of proteins, and their sequence is determined in the genome. Deficiencies of essential amino acids in an animal's diet reduce the rate of protein synthesis but do not lower the level of the amino acids in proteins, resulting in amino acid profiles that are relatively constant (Mente et al 2002, Sissener 2018. Polychaete amino acid profiles are therefore assumed to remain similar irrespective of diet, but differences be tween species are to be expected (Limin et al 2006).…”

n-3 Canola oil effectively replaces fish oil as a new safe dietary source of DHA in feed for juvenile Atlantic salmon

“…The Norwegian, Scottish and Australian salmon industries have reported a significant decrease in the absolute amounts of EPA and DHA in salmon fillets and a concomitant increase in FA typical of terrestrial-derived lipid sources, reflecting the changes in the feed formulation throughout the years (1,2,(8)(9)(10) . In addition, the high inclusion levels of vegetable and/or animal oils rich in n-6 FA in salmon diets result in an associated increase in the n-6:n-3 ratio in fish organs and tissues, including fish fillets (11) .…”

Erucic Acid (22:1n-9) in Fish Feed, Farmed, and Wild Fish and Seafood Products

“…Although the retention of erucic acid (possibly including some in vivo production) appeared to increase with decreasing dietary levels in the present feeding trial, total erucic acid levels in the fish decreased with decreasing dietary levels. The retention of this fatty acid is also likely to be dependent on feed concentrations, as most other fatty acids are retained in salmon to a high extent when low levels are provided in the feed (like for erucic acid in the present trial), while the retention is much lower when feed concentrations are high [ 22 ]. In support of this, fish that were fed a HEAR diet (with erucic acid constituting 28.1% of dietary fatty acids) for 18 weeks, had only 6.5% erucic acid of the total fatty acids in heart triacylglycerols and 11.5% in muscle triacylglycerols [ 17 ].…”