Requirement of Tilapia for .ALPHA.-tocopherol.

Abstract

Feeding experiments were conducted to investigate the requirement of Tilapia for vitamin E and to see whether or not the vitamin E requirement of Tilapia is increased by elevating dietary lipid levels. No apparent deficiency symptom was induced in fish receiving diets of different levels of α-tocopherol with 5% of lipid, although fish fed with the tocopherol-free diet showed the lowest hepatosomatic index. The addition of more than 5mg of α-tocopherol per 100g diet completely prevented the appearance of this symptom. The concentration of α-tocopherol in the liver of fish receiving the tocopherol-free diet was lowest and increased as dietary tocopherol levels increased. The fish receiving diets containing 10% and 15% fish oil methyl esters without tocopherol began to show low appetite and reduced growth from the 3rd week of feeding and were low in growth and feed conversion efficiency. The supplement of 50mg α-tocopherol to these diets effectively improved these conditions. Elevation of the dietary lipid levels from 5 to 15%. in the diet containing 50mg of α-tocopherol reduced the concentration of α-tocopherol in the whole body. The results obtained in these experiments suggest that 5-10mg of α-tocopherol per 100g of diet containing 5% lipid should provide adequate protection in most practical Tilapia diets. The elevation of dietary lipid levels increased the tocopherol requirement of Tilapia, judging from the growth and mortality.