THE Norwegian Institute of Fisheries and Seafood Research (NIFES) has produced new recommendations for the vitamin and mineral supplements in the feed for Atlantic salmon.
It says this is necessary because of a shift from mainly marine ingredients to feeds where more than 70 per cent comes from plants.
For the past six years NIFES has been taking part in an EU project called 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 turns out 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,’ said Kristin Hamre, senior scientist at NIFES.
‘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.’
The old recommendations for micronutrients in feed were the result of trials conducted in the 1980s. The trials were largely performed on rainbow trout juveniles, and very few studies looked at salmon and adult fish.
‘Implementation of this new knowledge is important for the growth and welfare of the salmon,’ said Hamre.
‘Lack of micronutrients can be fatal for the fish. Too little of just one nutrient is enough to cause problems.’
She explained that farmed salmon feed has changed dramatically the last 10 to 15 years. 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.
Hamre added: ‘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 fishmeal and fish oil do. That is why we need to adjust the amount of micronutrients.’
Through the Arraina project, NIFES scientists have now created nutrient packages of all the micronutrients, which they have added in graded levels to the feed.
They have tested it on both small fish in freshwater and smolt in seawater, and they are now conducting long-term studies on bigger fish.
The scientists are currently working their way through the list of vitamins and minerals, and have so far covered vitamin C, vitamin E, eight different B vitamins and several minerals.
They are 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.
They use biomarkers such as the concentration of vitamins in tissue, which is a very effective method that yields results quickly. It is a screening approach, and studies should be conducted of individual nutrients as a follow-up.
Hamre explained: ‘Previously, scientists could spend their whole career doing these types of studies. The new methods and tools mean that we get results much quicker.
‘It is nonetheless our preliminary approach to the issue, in 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.’
In a separate study, the Norwegian Food Inspectorate has submitted samples of Norwegian produced salmon for laboratory analysis and the results show that the omega-3 level in farmed salmon has decreased over the past 10 years, because large parts of today’s salmon feed are plant- and not fish based.
Picture: Kristin Hamre, senior scientist at NIFES