| Summary: | During the recent years, the composition of salmonids diets has changed from the use of mainly marine-based ingredients (e.g. fish meal and fish oil) to an increased use of plant-based ingredients (e.g. soybean meal and vegetable oil). These changes in diet composition have an impact on the mineral concentration and mineral availability. For instance, zinc (Zn) is naturally present in both fish meal and plant-based ingredients, but in different concentrations. The Zn concentration is usually higher in fish meal than in plant-based ingredients so, with the increased use of plant-based ingredients the Zn concentration tends to decrease in the basal mixes. In addition, compounds from plantbased ingredients can reduce mineral availability. For instance, phytic acid, which is typically found in plant-based ingredients, can decrease mineral availability due to its high binding affinity for metal ions. Therefore, minerals such as Zn, selenium (Se) and manganese (Mn) are supplemented to diets to cover the nutritional requirement of farmed fish. These minerals may be added as organic or inorganic forms. Taken all of this information into consideration, there is a need to study mineral availability in the current salmon feed composition which is formulated mainly using plant-based ingredients. Further knowledge in this area will provide a better understanding regarding mineral availability and necessary strategies to increase mineral availability in Atlantic salmon. Increasing mineral availability will promote fish health and robustness, but also decrease the environmental load via faeces. Considering that several chemical species of minerals can be present in a fish feed, it was hypothesised that availability is affected by the chemical species. For that purpose, analytical methods were optimized for extraction, quantification and identification of Zn chemical species in fish feed. This included method optimization by fractional factorial design and evaluation of sample extracts by size exclusion chromatography coupled ...
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