HEALTH AND FLESH QUALITY OF ATLANTIC SALMON Salmo salar FED A MODERN LOW FISHMEAL DIET SUPPLEMENTED WITH ANTARCTIC KRILL Euphausia superba
Atlantic salmon ( Salmo salar L.) were fed a commercially relevant diet with 15% fishmeal (control group) or the same diet substituted by 12% Antarctic krill meal (k rill group). The isoprotein (35%) and isolipid (35%) diets were fed to quadruplicate net pens (125m3; average seawater temperature 11°C) during a 10-week period, autumn 2017. The body weight increased from 2.2 to 3.9kg during the experimental period, corresponding with a thermal growth coefficient of 3.88 and 3.92 for control and k rill group, respectively. The average feed conversion ratio was 1.1. The krill group had a more voluminous body shape compared with the control group (higher condition factor ). The hepatosomatic and cardiosomatic indices were similar for the dietary groups, but the livers of the k rill group were darker and the amount of visible fat on the heart was significantly lower. Microarray analyses of liver tissue revealed that dietary treatment affected a large number of immune genes, and a panel of structural genes were upregulated in the livers of salmon fed the k rill diet, including cadherin and connexin (tight junction proteins). Gene enrichment analyses revealed that sugar metabolism was stimulated in fatty hearts and a significant downregulation was observed for complement genes and the retinoid metabolism. Additionally, downregulation of extracellular matrix proteins, including collagens and glycan's, indicated weaker tissue structure of the control group. Fillets of salmon fed the krill diet had firmer texture, more intense red coloration, and the problem with fillet gaping was lower (i.e. improved muscle integrity). It is concluded that dietary inclusion of krill meal in modern low fishmeal diets has a positive effect on health and on fillet quality of Atlantic salmon.
