Modulation of selenium tissue distribution and selenoproteins expression in Atlantic salmon (Salmo salar L.) fed diets with graded levels of plant ingredients

Increased substitution of marine ingredients by terrestrial plant products in aquafeeds has proved to be suitable for Atlantic salmon farming. However, a reduction in omega-3 long-chain polyunsaturated fatty acids is a consequence of this substitution. In contrast, relatively little attention has been paid to the effects of fish meal and oil substitution on levels of micronutrients such as selenium (Se), considering fish are major sources of this mineral for human consumers. To evaluate the effects of dietary marine ingredient substitution on tissue Se distribution and the expression of Se metabolism and antioxidant enzymes genes, Atlantic salmon were fed three feeds based on commercial formulations with increasing levels of plant proteins (PP) and vegetable oil. Lipid content did not vary at any sampling point in flesh, whereas was higher in fish fed higher PP in liver of 1 kg fish. Fatty acid content reflected dietary input and was related to oxidation levels. Liver had the highest Se levels, followed by head kidney whereas the lowest contents were found in brain and gill. The Se concentration of flesh decreased considerably with high levels of substitution, reducing the added value of fish consumption. Only brain showed significant differences in glutathione peroxidase, tRNA selenocysteine associated protein 1 and superoxide dismutase expression, whereas no significant regulation of Se related genes was found in liver. Although Se levels in the diets satisfied essential requirements of salmon, high PP levels led to a reduction in the supply of this essential micronutrient