Zinc gluconate and zinc sulphate as dietary zinc sources for Atlantic salmon

Different chemical forms of essential minerals and trace elements supplemented to feed may show different bioavailability in fish. The present experiment was performed to compare an organic zinc form (Zn-gluconate) with zinc sulphate as dietary zinc sources for Atlantic salmon. Triplicate groups of fish were fed commercial fish meal based diets supplemented with either a low zinc level (50 mg Zn kg−1) or medium zinc level (180 mg Zn kg−1) as zinc gluconate or zinc sulphate for 6 months. Growth, mortality and feed conversion were recorded through the experiment. Fish were sampled initially and every month for zinc status analyses measured as whole-body zinc concentration. After 4 and 6 months, vertebral zinc concentration was measured and serum zinc was analysed at the end of the experiment. There were no differences in growth or mortality during the experiment. The results showed a significant effect of dietary zinc supplementation level on zinc status in fish for both zinc forms. However, there were no differences in zinc status between groups given different zinc forms. In conclusion, the present experiment showed that zinc sulphate and zinc gluconate are equally efficient as zinc supplements in salmon feeds within the concentrations normally found in salmon feed.