Introduction
Fish are an important component of human nutrition due to their high dietary value, particularly as a source of the essential long-chain polyunsaturated fatty acids (LC-PUFA) EPA (20:5 n���3) and DHA (22:6 n���3). Since fish cannot synthesise omega���3 fatty acids de novo, these must be provided through the diet, with fish oil conventionally serving as the primary source (Tocher, 2015). In the context of sustainability and limited wild fish stocks, alternative lipid sources are gaining increasing attention. However, plant oils do not supply EPA or DHA, leading to declining omega���3 levels in farmed fish. The stilbenoid resveratrol, naturally occurring in grapes, has been shown to increase EPA and DHA levels in rainbow trout when included in the diet (Torno et al., 2017). Because resveratrol can reduce feed intake, lecithin may help counteract this effect by improving palatability (Kaiser et al., 2024; Tocher et al., 2008). Ahiflower oil, rich in stearidonic acid (SDA, 18:4 n���3), offers an additional opportunity to enhance endogenous LC���PUFA biosynthesis. Combining rapeseed oil, resveratrol, lecithin, and ahiflower oil may therefore represent a promising strategy to increase EPA and DHA levels in fish without relying on marine resources.
Materials and Methods
Four diets containing different combinations of rapeseed oil, ahiflower oil, and a lecithin mixture were formulated. Each of these diets was additionally prepared with resveratrol, resulting in eight experimental diets. A fish���oil���based diet served as the control. A 62���day feeding trial with Atlantic salmon was conducted in a RAS facility at Fraunhofer IMTE. Fish were fed twice daily on weekdays and once daily on weekends to apparent satiation.
Results and Discussion
Diets containing rapeseed oil, ahiflower oil, lecithin, or their combinations supported feed intake, feed conversion ratio, and specific growth rate comparable to the fish���oil control. In contrast, the inclusion of resveratrol reduced all growth���related parameters, likely due to decreased feed intake. Ahiflower oil significantly increased total omega���3 fatty acid levels in whole���body fish samples, in line with studies regarding rainbow trout (Fickler et al., 2018). Particularly, fish receiving ahiflower oil showed elevated ALA, SDA, and EPA contents. Interestingly, resveratrol supplementation lowered EPA levels, which may also be linked to reduced feed intake.
Conclusion
Plant���derived lipid sources show strong potential as sustainable alternatives to fish oil in salmon diets. Ahiflower oil effectively increased omega���3 fatty acid levels, including EPA, in Atlantic salmon. The lecithin mixture proved to be a suitable lipid component, supporting growth and maintaining fatty acid profiles comparable to fish oil. Resveratrol, however, appears unsuitable for Atlantic salmon due to its negative effects on palatability and growth performance.
Acknowledgment
This work was supported within the Fraunhofer and DFG transfer programme.
References
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