Effects of lysine administration on plasma arginine and on some nitrogenous catabolites in rainbow trout

Abstract

1. 1. Rainbow trout were fed either graded levels of lysine (0.8, 1.8 and 3%) at a constant level of arginine (1.4%) or excess arginine (2.4%) at a fixed level of lysine (1.8%). 2. 2. Increasing the dietary lysine level affected plasma urea, plasma arginine and ammonia excretion. 3. 3. Trout fed graded levels of lysine received an arginine challenge (U 14C- l-arginine) and it was found that excess dietary lysine led to a decrease in arginine degradation. 4. 4. Injection of l-lysine induced a decrease in urea excretion, while injection of l-arginine increased both urea and ammonia excretion in control well-fed trout. 5. 5. These results are discussed in the light of current knowledge on the antagonism between lysine and arginine.