The relationship between an elevated serum amino acid ratio and the development of other biological abnormalities in the experimentally malnourished pig.

I. Weanling pigs were fed under three dietary regimens, control, low protein and total calorie restricted. 2. In the protein-deficient group the amino acid ratio did not start to become elevated until growth was impaired and total serum protein and albumin concentration began to fall. 3. In the protein-deficient group, but not in the control or undernourished animals, the magnitude of the ratio was statistically correlated with the rate of growth, appetite, serum protein and albumin concentration and hydroxyproline excretion. 4. The results provide information on the relationship between the serum amino acid ratio and nutritional status.