Nutrition of Salmonoid Fishes

Abstract

Tocopherol-deficient diets containing 1 or 5% of stripped herring oil were supplemented with zero, 10, 20, 40 and 80 mg of α-tocopherol/100 g of dry diet and were fed to duplicate lots of chinook salmon (Oncorhynchus tshawytscha) fingerlings for 24 weeks. Separate lots of fish were fed diets containing 1% of trilinolein and supplemented with 10, 20, 40 and 80 mg of tocopherol/100 g of dry diet. In a second feeding trial the diet containing 5% of herring oil was supplemented with 2.5, 5.0, 10, 20 and 40 mg of tocopherol/100 g of dry diet and was fed to duplicate lots of fish. The deficiency syndrome included: poor growth; exophthalmia; ascites; erythrocyte fragility; anemia; clubbed gills; epicarditis and ceroid deposition in the spleen. The symptoms were more severe in the fish fed the unsupplemented diet containing 5% of herring oil than they were in the fish fed the 1% herring oil diet and were not observed in fish fed diets supplemented with tocopherol. Under the experimental conditions used, a requirement of less than 3 mg of α-tocopherol/100 g dry diet was indicated. The herring oil used in diet preparation contributed 0.5 mg of tocopherol/100 g of dry diet (0.1 mg/g oil).