The relationship between dietary lipid levels and .ALPHA.-tocopherol requirement of rainbow trout.

Abstract

Feeding experiments were conducted to investigate the relationship between the requirement for tocopherol and dietary lipid levels in rainbow trout, and to see whether the vitamin E deficiency of rainbow trout could be induced by elevating dietary lipid levels. The apparent deficiency symptom was induced for the first time in rainbow trout by feeding them with a diet containing 15% pollock liver oil methyl esters. The fish receiving this diet without tocopherol began to show low appetite and reduced growth ratefrom the 6th week of feeding and were lowest in weight gain. The fish also began to show severe convulsions and to die from the 7th week; 40% of the fish died before the end of the experiment. The addition of 5 mg of α-tocopherol per 100g diet completely prevented the appearance of this syndrome and effectively improved growth to a rate comparable to that of the control group. The tocopherol requirement and the tissue storage of α-tocopherol in rainbow trout were also found to be greatly affected by the degree of unsaturation of the fat in the diet. Judging from the appearance of the apparent deficiency symptoms and the concentration of tocopherol in the livers. around 10 mg of α-tocopherol per 100g of diet containing 15% lipid should provide adequate protection in most practical rainbow trout diets.