Dietary inclusion inclusion of Durvillaea antarctica meal and rapeseed (Brassica napus) oil on growth, feed utilization and fillet quality of rainbow trout (Oncorhynchus mykiss)

Durvillaea antarctica is a brown seaweed that can be located in the Southern Hemisphere and has a high content of polyunsaturated fatty acids and gamma-tocopherol. Aquaculture currently uses vegetable oils for feeding rainbow trout (Oncorhynchus mykiss), but this reduces the omega-3 levels in the fillet. The aim of this study was to evaluate the effect of dietary inclusion of D. antarctica meal on the fillet quality of rainbow trout fed with rapeseed oil. A total of 375 rainbow trout (17.6 +/- 0.46 g) were randomly assigned to five treatments with three replicates (25 fish per replicate) in 15 tanks and reared for 9 weeks. Rainbow trout fed with 100% fish oil were considered as a positive control. A negative control corresponded to a diet with a mix of 10% fish oil and 90% rapeseed oil. This diet was used for the other three treatments with the inclusion of 1.5, 3 and 6% of D. antarctica meal respectively. At the end of the feeding trial, the fish were euthanized to evaluate growth, feed utilization and fillet quality. The diets did not affect the growth and feed utilization. However, the fillet of fish fed with 6% D. antarctica meal showed a less acidic pH, higher luminosity, less yellowing and color saturation, compared with the other groups. The fillet of fish fed with D. antarctica meal and rapeseed oil, showed less oxidation. The fatty acid profile was affected by the inclusion of rapeseed oil, reducing the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, diets with D. antarctica meal were able to partially compensate the fish oil intake by reducing some saturated fatty acids, increasing the EPA content and reducing the atherogenic index and thrombogenic index, improving the nutritional value of the fillet. Although the use of D. antarctica meal does not significantly compensate for the effects of rapeseed oil on the fillet, it could be used as an alternative to increase the nutritional value and quality of rainbow trout.

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