October 12, 2017
A research institute said the amounts of vitamin and mineral supplements in the feed for Atlantic salmon must be adjusted in line with the changing composition of salmon feed from being fish-based to plant-based.
The Norway-based National Institute of Nutrition and Seafood Research (NIFES) pointed out that a shift from mainly marine ingredients to feeds where more than 70% comes from plants has changed the requirements, adding that implementation of this new knowledge is important for the growth and welfare of the salmon.
"Lack of micronutrients can be fatal for the fish. Too little of just one nutrient is enough to cause problems", said Kristin Hamre, senior scientist at the NIFES.
NIFES said that while most of the feed was previously composed of fish meal and fish oil, most commercial salmon feeds now contain more than 70% plant ingredients.
It said plants contain anti-nutrients that can cause the fish to absorb less of the nutrients in the feed and, in some cases, the salmon therefore need different quantities of vitamins and minerals.
'Even if the plants contain these nutrients, the fish are unable to absorb them to the same extent as they would from marine feeds. Plant ingredients also contain lower levels of some nutrients than fish meal and fish oil do. That is why we need to adjust the amount of micronutrients", said Hamre.
Since 2011, NIFES has been part of the EU project Arraina, the goal of which is to find out how much micronutrients different species of fish need now that the composition of the feed has changed. Norway and Scotland have collaborated on the part of the project that concerns salmon.
It was found that for some of the vitamins and minerals studied so far, the old recommendations are far from what the fish actually need.
"When we first saw the results, we could hardly believe our eyes. For example, when the results for the B vitamin niacin came in, it turned out that salmon needs four times as much niacin as previously recommended, and twice as much vitamin B6", Hamre said.
Through the Arraina project, NIFES scientists have created nutrient packages of all the micronutrients, which they have added in graded levels to the feed.
The scientists have reviewed vitamins C and E, eight different B vitamins and several minerals, using a method where they look for the level of all micronutrients in one and the same trial, instead of studying one at a time.
'…[I]n the future we will study selected nutrients in more detail. With increasing use of plant ingredients in the feed, it is important that we find the right supplementation of vitamins and minerals to ensure good growth and robust and healthy fish", Hamre said.