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

Abstract

1. Diets containing varying levels of crude protein (CP) in the range 9.5–18.5% with and without supplements of diammonium citrate (DAC) as a source of non-protein nitrogen (NPN) were given to 160 growing chicks from 2 to 4 weeks of age, and their livers were assayed for glumate dehydrogenase (GDH) activity.2. Growth rate and total liver protein were increased by raising the protein level from 9.5 to 18.5% CP. Chicks receiving 9.5 or 12.5% CP were heavier when they had also received 1.94% DAC. At 18.5% CP the addition of 3.88% 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. It was concluded that liver GDH activity did not provide a useful index of the utilization of NPN.