A full factorial design to investigate interactions of variable essential amino acids, trace minerals and vitamins on Atlantic salmon smoltification and post transfer performance

To contribute in knowledge for the development of safe, efficient and sustainable functional salmon diets, we ran a feeding trial applying a 23 full factorial design to investigate combined effects, on Atlantic salmon smoltification and post transfer performance, of variable supplementation levels of essential amino acid (Lys, Met, Thr and Arg), essential trace mineral (Zn, Fe and Se) and vitamins (E, C and astaxanthin as provitamin A) premixes in low fishmeal diets, using crystalline amino acids, organic trace minerals and synthetic vitamins, respectively. The nutrient levels used in our study were chosen to meet the known requirements of fish reflecting the variation in commercial feeds. Fish performance, nutrient digestibility, skin, and intestinal health were evaluated in Atlantic salmon parr-smolt, the latter by means of qPCR, global transcriptomics, and immunohistochemistry. The results revealed the potential for significant improvement of salmon post smoltification growth by simultaneous dietary level increase of Met, Lys, Thr and Arg (5% higher body weight increase). Significantly negative effect on fish post transfer growth and survival (22.5 % lower body weight growth and 2.6 times higher mortality) was observed in the high dietary vitamin supplementation treatments which was not present in the simultaneous high trace mineral and vitamin supplementation treatments (8% higher body weight increase and 2.8 times lower mortality in the high trace mineral supplementation treatments). In the high trace mineral supplemented dietary treatments was also observed improved FCR (8.5 %) and a further improvement in performance was seen in the treatments with simultaneous high essential amino acid and trace mineral supplementation levels (12.6 % higher body growth increase). Redox-sensitive gene and extracellular matrix components' gene transcription effects and compensatory mechanisms on protein and energy metabolism, immune modulation, skin repair systems and erythropoiesis were observed by transcriptomic and histological analyses in response to the variable dietary essential nutrient levels.