Effects of dietary protein levels on free amino acid and glutathione contents in the tissues of rainbow trout

Abstract

1. Rainbow trout were fed the high protein and low protein diets for 15 days using casein as the protein source. Levels of free amino acid and glutathione in liver and muscle, and composition of excreted amino acids were determined. 2. The free amino acid level in the tissues was higher in the group of fish fed high protein diet than the group of fish fed low protein diet. 3. There was no significant difference in hepatic glutathione content between the high protein diet group and low protein diet group. However due to the difference in the liver sizes between the two groups, the total hepatic glutathione, when computed based on the total body weight, was appreciably higher in the high protein diet group. 4. The amount of amino acid excreted by the fish on the body weight base and the amino acid composition were very similar between the fish fed the high protein and the low protein diets.