Histopathological and haematological changes in amago salmon, Oncorhynchus rhodurus (Jordan & McGregor), fed a vitamin-D-free diet

Two purified diets supplemented with 0 or 20 000 IU vitamin D₃ kg^?1 of diet were fed to amago salmon, Oncorhynchus rhodurus (Jordan & McGregor), for 22 weeks. The feeding stopped when fish with deficiency signs including reduced growth, and caudal region and fin tip damage increased in number. Deficient fish had a thinned epidermis consisting of atrophied and necrotic epidermal cells over the basal cells. In lesions of the caudal peduncle, the skin and the underlying musculature were extensively necrotized. The liver showed degenerated and necrotic hepatocytes. Respiratory epithelium and cardiac muscle fibres were swollen. Hypocalcaemia was evident. No pathological changes were found in bone, eyes, brain and alimentary tract. The control groups fed a nutritionally complete diet grew well and displayed no pathological changes. The pathological changes were reversed after 4 weeks of feeding of vitamin-D₃-suppliemented diet.