Aquaculture feed.
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New research from the Norwegian University of Life Sciences (NMBU) suggests that salmon farms could sharply reduce phosphorus discharges by adopting feed tailored to their production systems.
According to the researchers, the Norwegian aquaculture industry uses almost as much phosphorus as agriculture, and losses of unused nutrients into the water are an ongoing environmental concern in several fjord systems.
The research findings indicate that feed designed for land-based aquaculture facilities can improve phosphorus uptake in salmon and potentially reduce losses by as much as 90%. The university states that these results could help producers remain within strict environmental thresholds. Phosphorus is essential for fish growth, but when it is not absorbed, it can enter surrounding waters and contribute to eutrophication.
Vegard Øvstetun Flo, who carried out the research as part of his doctoral work in collaboration with his employer, Cargill, said the project has identified several feed-related adjustments that influence how phosphorus behaves in production systems.
“We have shown that system-adapted feed can make phosphorus particles easier to capture, and that less vitamin D in the feed reduces the amount of dissolved phosphorus in the faeces,” he said.
NMBU noted that some of these insights have already been incorporated into commercial feeds now available to farmers.
According to NMBU, the study aimed to build knowledge that would allow the sector to lower phosphorus inputs and emissions without compromising animal welfare. The research examined how feed formulation, water temperature and facility design affect both the nutritional needs of salmon and the ability of drum filters to remove phosphorus-bearing particles from the water.
The work also found that fish reared in colder conditions appear to require less phosphorus than those kept at higher temperatures.
NMBU highlights that most phosphorus leaves the fish in particulate form, although the size and durability of these particles differ depending on the diet. This variation affects how efficiently standard filtration systems remove them.
The study also concludes that adjusting vitamin D levels influences the amount of dissolved phosphorus, which is harder to capture.
The NMBU research adds to a growing body of studies assessing how the industry might reduce its demand for a resource that is finite and cannot be regenerated.
"In the longer term, this type of research may form the basis for better regulation, new modelling tools, and economic incentives for improved phosphorus management. In this way, it can contribute to more sustainable growth in Norwegian aquaculture," NMBU stated.
The NMBU news comes in the same week the Norwegian Government's advisory group on sustainable feed delivered its report with 20 measures to achieve the goal of sustainable feed production by 2034.
Norwegian authorities have created a national "targeted mission" on sustainable feed, with Norwegian Minister of Agriculture and Food, Nils Kristen Sandtrøen, arguing that "Norwegian food production depends on safe and stable access to feed."
"With this report, we receive concrete recommendations that can help strengthen preparedness, environmental considerations, and value creation across the entire country," he stated.