The limited availability of fish oil, rich in health-promoting omega-3 long-chain polyunsaturated fatty acids, is one of the major constraints for further growth of the aquaculture industry. Long-chain n-3 rich oils from crops GM with algal genes are promising new sources for the industry.

Norwegian and Australian researchers studied the use of docosahexaenoic acid (DHA) omega-3 canola oil (DHA-CA), genetically modified with algal genes, to replace fish oil in diets of Atlantic salmon fingerlings, as part of two feeding trials in Australia and Norway. Two dietary levels of DHA-CA were compared with two dietary levels of fish oil at two water temperatures.

Fish increased their weight approximately 20-fold at 16°C and 12-fold at 12°C during the experimental periods, with equal growth in salmon fed the fish oil diets compared with DHA-CA diets. Salmon fed DHA-CA diets had approximately the same EPA+DHA content in whole body as salmon fed FO diets. Gene expression, lipid composition and oxidative stress-related enzyme activities showed only minor differences between the dietary groups, and the effects were mostly a result of dietary oil level, rather than the oil source.

Researchers found that the levels of phytosterols, vitamin E and minerals in the n-3 modified canola oil fall within the natural variation of commercial canola oils and levels of undesirable compounds were undetectable. Researchers conclude that the n-3-rich modified canola oil (DHA-CA) is as safe as other commercial canola oils and is suitable as an alternative oil source in salmon diets.

The work will be presented at the World Congress on Oils & Fats 2020 in Sydney, Australia.

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