Influence of Intermittent Protein Intake Every Few Days on Rat Growth and Metabolic Function

Infantile rats were fed over a period of 5 weeks according to plan ingesting 20% casein and protein-free diets alternately every few days, and were examined for their growth and changes in metabolic function from the viewpoint of protein nutrition. Three groups of rats fed with the two diets alternating everyone, two or three days were almost equal in growth to one another. However, their growth rates increased intermittently to such an extent as to be half that of the control fed ad libitum with the 20% casein diet. Two groups of rats given the 200/0 casein diet for one day and followed by two or three protein-free days showed much more growth-lag than the former groups did. The extent of body weight gain seemingly responded to the amount of protein intake as a whole throughout the experimental period. A change in metabolic function was observed for the hepatic RNA/DNA ratio in the animals receiving the protein-free diet for a few days prior to sacrifice. A similar indication was shown as to decreased levels of branched-chain and aromatic amino acids in the plasma, which didn't reach their normal level even after subsequent feeding with the 20% casein diet. Urinary nitrogen and urea excretions, which were markedly lowered by ingesting the protein-free diet for a few days, gradually returned to the normal levels within a few days after feeding instead with the 20% casein diet. Some metabolic functions were appreciably affected by unbalanced feeding that resulted in a variation in protein nutrition.