| Summary: | Selenium (Se) is an essential element for humans, as well as for fish, including Atlantic salmon (Salmo salar). One of the main sources of Se and other elements for farmed salmon is the diet. Due to the replacement of marine-based ingredients with plant-based ingredients in fish feed, supplementation of Se has been considered necessary to maintain normal functions in fish. There are different chemical forms of Se, often characterized as Se species. Se species can be either inorganic or organic. Organic Se has higher a bioavailability than inorganic Se. However, inorganic Se is considered more toxic than organic Se. Other elements, such as the essential elements cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), and non-essential elements such as cadmium (Cd), mercury (Hg), lead (Pb) and arsenic (As), may also be present in salmon. Some of these elements are known to interact with Se, but few studies have investigated the effects of the Se species on the interactions between Se and other elements. In fish feed, Se can be supplemented, both in forms of inorganic Se (e.g. selenite) and as organic Se (e.g. selenomethionine (SeMet) or SeMet produced by Se-enriched yeast. Maximum limits have been established for Se as a feed additive for animals by the European Commission, set to a total of 0.5 mg Se/kg. For SeMet and SeMet produced by the Se-enriched yeast (Saccharomyces cerevisiae), the limit is set to 0.2 mg Se/kg. Due to this difference in legislation for the supplementation of Se species, there is a need for analytical methods that can discriminate between the different Se species. In this thesis, the overall aim was to apply chemometrics and other statistical approaches for handling data obtained from salmon a feeding trial with Atlantic salmon, and for the method optimization for determining Se species in fish feed and feed ingredients. This study evaluates the correlations between Se and other elements in salmon fed with feed supplemented with inorganic or organic Se species. ...
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