The Surveys on the Urea and Allantoin Excretion and Other Criteria from Rats Fed “Threonine Imbalanced” or “Corrected” Diet

Abstract

Weanling male rats of Wistar strain were fed ad libitum 7 or 8% casein-α-starch diet supplemented with 0.3% DL-methionine with (+Thr) or without (-Thr) added 0.36% DL-threonine for 12 days. Urine was collected 3 times for 3 days each at one-day interval. The urine sample was analysed for allantoin, urea and total N. There was no difference between the values of growth rate, liver and carcass fat con-tent, protein efficiency ratio and % N retention of -Thr and +Thr groups, whereas urea excretions of -Thr groups were significantly higher (over 2 times) than those of +Thr and allantoin excretions were consistently lower in the former when dietary protein level was 8%. These results suggest again that urinary urea may be a most sensitive external indicator for detecting the differential changes in body protein metabolism, which are caused by slight modification of dietary amino acid composition.