APPORTIONING VALINE REQUIREMENTS FOR MAINTENANCE VERSUS GROWTH FOR RATS

Purified diets containing six different concentrations of valine were fed to growing rats to determine the valine requirements for maintenan ce and growth. A model was employed to subdivide the valine requiremen t for maintenance from its requirement for growth. Based on weight gai n response, the valine need for growth was 8.28 mg/g live weight gain and the daily maintenance need was 0.40 times metabolic body size (W-g (.75)). Based on nitrogen gain response, the valine need for growth wa s 0.33 mg/mg N gain and the daily maintenance need was 0.44 times meta bolic body size (W-g(.75)) Th, plateau of plasma valine concentration was reached at 69 m/iday. Previous valine requirements for growth and for maintenance were in close agreement with these estimates. As a per centage of retained protein, according to these equations, valine was calculated to be 5.3%; the reported valine concentration of rat muscle crude protein is 6.9%.