The effects of dietary protein and non-protein nitrogen on liver glutamate dehydrogenase activity in the chick.

I . Diets containing varying lcvels of crude protein (CP) in the range 9.5-18.5 "/b with and without supplements of diammonium citrate (DAC) as a source of non-protein nitrogen (KPN) were given to 160 growing chicks from z to 4 weeks of age, and their livers were assayed for glutamate dehydrogenase (GDH) activity. 2. Growth rate and total liver protein were increased by raising the protein level from 9.5 to 18.5 76 CP. Chicks receiving 9'5 or 12.5 : / o CP were heavier when they had also received 1.94 "/o DAC. At 183 76 CP the addition of 3.88 "/b DAC depressed growth. 3. GDH activity per unit liver weight and total GDH activity increased with dietary protein level but there were no consistent responses to DAC supplements. I t was concludcd that liver GDH activity did not provide a useful index of the utilization of NPN.