Abstract
The effects of a urea supplement to a low-protein diet on growth rate, nitrogen balance, and plasma free amino acid concentration were investigated in growing rats. Rats fed 20% casein, 5% casein, or 5% casein supplemented with urea for about 5 weeks were compared. In rats fed the 5% casein diet supplemented with urea, the growth rate was higher, the nitrogen balance was more positive, and the retention of nitrogen was greater than in rats fed the 5% casein diet without the supplement. Of the plasma free amino acids, essential amino acids were increased by the supplement, and the essential/non-essential amino acid ratio was higher. The supplementation of a low-protein diet with urea thus caused a favorable change in the pattern of amino acid metabolism to one of synthesis of body protein.
