| Summary: | Post-juvenile Atlantic salmon (Salmo salar) were fed to satiation, twice daily for 126 days,with diets supplemented with copper (10 or 35 mg/kg), iron (333 or 1000 mg/kg)/'and unoxidized or oxidized dietary lipid measured as peroxide value (PV, <5 or <5+ or 35+ meq/kg). The dietary effects measured include growth performance, general health, flesh proximate and fatty acid composition, and in situ oxidative stress. Lipid peroxidation in the fishmeal and fish oil was controlled by adding ethoxyquin (150 mg/kg) to diets containing unoxidized dietary lipid (<5 meq/kg). All diets contained the required level of vitamin E (30 IU/kg). Diets supplemented with the highest level of iron, without anti-oxidant protection (no ethoxyquin), showed the greatest loss of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) and vitamin E (p<0.05). Fish fed these diets displayed significantly (p<0.05) decreased growth, feed intake, feed efficiency, and utilization of gross energy and protein that were attributable to the losses of the preceding essential nutrients and possibly dietary protein modification. Dietary vitamin E concentrations decreased in all diets, except those with low levels of iron and peroxide values, during the 126-day study period. Diets without anti-oxidant supplementation had significantly (p<0.05) higher lipid peroxidation levels as compared with anti-oxidant-containing diets. However, fish hepatic and muscle tissue lipid peroxidation were unaffected. Autopsy-based assessments of general health indicate that fish fed diets influenced by iron-catalyzed lipid peroxidation exhibited clinical signs of poor health indicative of dietary vitamin E and omega-3 highly unsaturated fatty acid deficiency. These results suggest that fish diets undergoing ironcatalyzed lipid peroxidation with attendant deficiencies in omega-3 highly unsaturated fatty acids and vitamin E adversely influence the growth performance, general health, and fillet proximate and fatty acid composition of post-juvenile Atlantic salmon. The consumption of oxidized dietary lipids by the experimental fish did not influence in situ oxidative stress parameters as measured in this study. Land and Food Systems, Faculty of Graduate
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