Introduction
Atlantic salmon farming is regarded one of the most profitable and successful aquaculture industries, especially for Norway, Chile and Canada (Asche et al., 2013). To keep the production cost low, salmon feed industry has gradually shifted from marine to terrestrial plant ingredients (Aas et al., 2019). However, the use of such ingredients can have negative effects on the growth performance and health status of the fish. Therefore, microorganisms and their extracted oil, are likely to be more suitable and sustainable ingredients for the near future, due to several factors such as vitamin and mineral content, good amino acid profile, sterols, folic acid, nicotinic acid, and the capability for producing omega-3 LC-PUFA fatty acids and especially DHA (Taelman et al., 2013, Kousoulaki et al., 2013). This fatty acid is crucial for the growth, physiology and disease resistance for both fish and humans.
Materials and Methods
The trial was performed at LetSea, Dønna Norway, with the aim to evaluate the potential of Schizochytrium oil (Veramaris - VMO), partially or total replacing the fish oil. After the acclimation period, fish were randomly distributed to 9 fiberglass tanks, 200 fish/tank. There were three different dietary treatments, in triplicate, with three levels of Veramaris, 0% VMO, 50% VMO and 100% VMO. After 49 days of feeding, weights were recorded and various samples were collected and preserved for further analysis, such as histomorphometry of the intestines and gills, expression selected genes in the gills, and assessment of the welfare status. Fish were also assessed for saltwater tolerance in 33 ppm saltwater after the feeding period.
Results
The results have so far showed that fish fed the 50% VMO diet tended to have higher growth performance. No fish mortality was observed in fish moved to salt water. Algal oil appeared to improve the height of the intestinal folds, both in distal and anterior part, although no significant changes were observed among the treatments. Gill morphology, and gene expression involved in immunity are underway.
Conclusions
The present study has revealed so far that using of algal oil can improve the growth of fish and intestinal fold height in Atlantic salmon. Further analysis of gill morphology and gene expression involved in immunity will help to explore the physiological functions and immune responses during smoltifications when algal oil is used in the diet.
Acknowledgements
This work has been funded by the NordForsk (Project No. Non For 700-551)
References
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Aas, TS, Ytrestøyl, T, Åsgård, T, 2019. Utilization of feed resources in the production ofAtlantic salmon (Salmo salar) in Norway: an update for 2016. Aquac. Rep. 15, 100216.
Taelman, SE, De Meester, S, Roef, L, Michiels, M, Dewulf, J, 2013. The environmental sustainability of microalgae as feed for aquaculture: a life cycle perspective. Bioresour. Technol., 150, 513-522
Kousoulaki, K, Østbye, T K K, Krasnov, A, Torgersen, JS, Mørkøre, T, Sweetman, J, 2015. Metabolism, health and fillet nutritional quality in Atlantic salmon (Salmo salar) fed diets containing n-3-rich microalgae. J. Nutr. Sci. 4, e24.