Effects of dietary pro- and antioxidants on some protective mechanisms andhealth parameters in Atlantic Salmon

Health aspects were investigated in postsmolt Atlantic salmon Salmo salar f ed high (below known toxic limit) or low (above the minimum requirement) di etary levels of vitamin E, vitamin C, astaxanthin, total lipid, iron, coppe r, and manganese using a 2(7-3) reduced factorial design. Hematocrit and he moglobin were positively affected by iron after 14 and 23 weeks of feeding. Red blood cell count was not influenced by the dietary differences. Phagoc ytic chemiluminescent responses were positively affected by vitamin E after 14 and 23 weeks, but serum complement-mediated hemolysis and lysozyme acti vity in serum and in head kidney were unaffected. Some biological effects o n endogenous antioxidants were positive effects of vitamin E on total super oxide dismutase activity in liver after 14 weeks and in muscle after 23 wee ks, negative effects of astaxanthin on muscle catalase activity, and positi ve effects of dietary lipid on liver glutathione and total mercaptans after 23 weeks. None of the measured biological responses were affected dramatic ally by the dietary variables, indicating that the fish seem to tolerate a large range of dietary pro- and antioxidants under normal rearing condition s.