Abstract
The increasing use of terrestrial plant lipids to replace of fish oil in commercial aquafeeds requires understanding synthesis and storage of long chain-polyunsaturated fatty acids (LC-PUFA) in farmed fish. Manipulation of dietary fatty acids may maximize tissue storage of LC-PUFA, through increased production and selective utilization. A data synthesis study was conducted to estimate optimal levels of fatty acids that may maximize the production and storage of LC-PUFA in the edible portion of salmonids. Data were compiled from four studies with Atlantic salmon, rainbow trout, and steelhead trout (total n = 180) which were fed diets containing different terrestrial-based oils to replace fish oil. LC-PUFA (%) were linearly correlated between diet and muscle tissue (p < 0.001; r2 > 44%), indicating proportional storage after consumption. The slope, or retention rate, was highest for docosahexaenoic acid (DHA) at 1.23, indicating that an additional 23% of DHA was stored in the muscle. Dietary saturated fatty acids were positively related to DHA stored in the muscle (p < 0.001; r2 = 22%), which may involve membrane structural requirements, as well as selective catabolism. DHA was found to be optimally stored with a dietary n-3: n-6 ratio of 1.03: 1. These new results provide a baseline of optimal dietary ratios that can be tested experimentally to determine the efficacy of balancing dietary fatty acids for maximum LC-PUFA storage.
Highlights
The need to reduce fish meal (FM) and fish oil (FO) levels in aquafeeds has become critical with the growth of the aquaculture industry
A segmented regression showed that the highest muscle tissue docosahexaenoic acid (DHA) levels when the dietary ratio of ALA: LNA was T = 1.03 ± 1.90 (SE, standard error of the estimate; Fig 2A), and the highest muscle tissue ARA levels were found at T = 0.62 ± 0.14 (Fig 2B)
Using Similarity in Percentages (SIMPER), we found that when fish were divided into four quartiles based on their diet DHA level, groups 1 and 3 were the most different (44% dissimilar), that is, showed the greatest difference in their tissue long-chain polyunsaturated fatty acids (LC-PUFA) content
Summary
The need to reduce fish meal (FM) and fish oil (FO) levels in aquafeeds has become critical with the growth of the aquaculture industry. This has been, and continues to be, a challenge because FM and FO provide unique nutrients that are required by finfish species, at varying levels depending on species and life stage. 20 carbons in length), namely the n-3 and n-6 LC-PUFA: eicosapentaenoic acid (EPA; 20:5n-3), docosahexaenoic acid (DHA; 22:6n-3), and arachidonic acid (20:4n-6) These LC-PUFA play numerous physiologically important roles essential to health of all vertebrates [1] and are primarily. Fish are the primary source of n-3 LC-PUFA for humans [3], and this has prompted interest in LC-PUFA metabolism in fish, with biosynthesis being one of the most targeted pathways under investigation
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