Landbased salmon can suffer from vitamin deficiency
A collaboration between Nordlaks, NMBU, UiS, FishLab and feed producer Skretting has documented for the first time that Atlantic salmon can produce vitamin D when exposed to sunlight. This is important to take into account for salmon produced indoors on land.
The study is published in Aquaculture Nutrition and according to Skretting provides new and important insight into the nutritional needs of salmon, and is an important contribution to research on fish health.
“This is a breakthrough in the understanding of how salmon obtain vitamin D. Previously, it was believed that fish only obtain vitamin D through their feed, but our results show that salmon in the sea can actually produce the vitamin themselves, in the same way as humans and other animals,” says David Knudsen, global innovation manager at Skretting, who led the study.
Extensive field studies
Skretting says that in recent years it has mapped the levels of vitamin D in salmon at different times of the year, in different production methods and fish sizes. The results show that salmon in open production facilities have vitamin D levels up to 20 times higher than fish in closed facilities. This is because salmon, like humans, can form vitamin D in their skin when exposed to sunlight.
“As more and more aquaculture is moved to land-based facilities, we must be aware that the fish do not have the same opportunity to produce vitamin D naturally. It may then be necessary to compensate with supplements in the feed or the use of UV light to ensure both fish health and nutritional quality for the end consumer,” says Knudsen.
Seasonal variations
Studies show that vitamin D levels drop significantly during the winter months and in fish raised indoors without access to sunlight. This may be a contributing factor to the increased incidence of wounds and infections during the dark season. Research on human nutrition indicates that sufficient vitamin D can contribute to better barrier function and faster wound healing.
“Although we have received new and important answers, there is still much we do not know about salmon’s nutritional needs and how vitamin D affects the fish’s health and welfare,” says veterinarian Christina Husebø at Skretting, who has been the driving force in the work of collecting the extensive data from facilities along the Norwegian coast.
“Collaboration with the fish farmers is crucial for us to take these knowledge steps together and thus lay the foundation for even more sustainable production in the future. For us, this means even more precise nutrition, ensuring that the fish get the right feed at the right time.”
The results are relevant to everyone working with fish health, nutrition and sustainability in the aquaculture industry.
The study was conducted on salmon from 15 different Norwegian farms, and shows clear differences between fish in the sea and fish in land-based systems.
Continued research
Although the importance of vitamin D for the immune system is well documented in humans and mammals, extensive research on fish is still lacking. Skretting continues to investigate the effects of different levels of vitamin D on salmon health, especially in relation to skin health and wound problems.
