Assessing the impact of novel feed ingredients on growth performance and behavior of juvenile arctic charr (Salvelinus alpinus).

Supervisors: David Benahim, Alexandra Leeper (Hólar University College, Iceland).
In a context of rising population, aquaculture is a good candidate to help to feed humanity. This industry faces some challenges to become sustainable and the use of fish meal (FM) as protein source in aqua feeds is one of the main reasons. It is an even greater challenge in the case of carnivorous fish, such as salmonids, considering their high protein demand. Plant protein sources, in particular soybean meal (SBM) thanks to its availability, appears to be the best option to replace FM for a fast implementation. However, SBM is known to contain anti-nutrional factors and dietary fibers such as non-starch polysaccharides. Enzymatic treatments or addition of prebiotic are shown to have the potential to enhance SBM. Protein replacement from FM to SBM proteins would have both economic and ecologic benefits for aquaculture production. This study has been conducted on juvenile Arctic charr (Salvelinus alpinus), a member of the Salmonidae family that has a great importance for Icelandic aquaculture. An important knowledge gap exists to know if it is possible to provide feeds with SBM inclusion to this species at early life stages without impacting welfare. This study aimed to answer this question with a feeding trial testing three baked-diets with a 25% inclusion of SBM. The first diet had an inclusion of untreated SBM (diet S), the second one diet had enzymatically treated SBM (diet SP), and the last one had untreated SBM but with an added prebiotic (diet SPE). Those three SBM diets were compared to a baked control diet with only FM protein (diet F). Finally, all the diets were compared to an industrial extruded diet (diet C). Another question was to know if any differences in terms of growth performance and behavior between SBM diets appeared. Welfare was assessed using three indicators: mortality, growth and behavior. Behavior assessment was done across two different contexts and repeated in order to identify potential presence of personality traits. The two personality traits chosen for this study were the shyness-boldness and activity traits. The results of this study at the individual level will be linked in the future to the gut microbiome and distal gut histology. This study showed that the use of a 25% inclusion of SBM as protein source in juveniles Arctic charr was a promising alternative to replace FM. The growth was significantly higher (15.7%) for the fish fed FM diets compared to the ones fed SBM diets, but one can consider growth is still comparable with the control diets (F and C). No mortality nor malformation were found which has been interpreted as a sign of good welfare. Behavior results showed differences between fish fed SP and SPE, with fish fed the other diets which could reflect an altered welfare from an internal point of view. The coming study of distal gut histology and gut microbiome assessment may elucidate if those changes are causing a degradation of the welfare as suggested by the author of this study or if the changes were reflecting an improvement of the welfare. The main conclusion from this study was that untreated SBM can be provided in formulated diets to juveniles of Arctic charr at a 25% inclusion without risk of negatively impacting the welfare of the animal. These results highlight great potential towards more sustainability for the future of Arctic charr production.