Multiple factors in short-term behavioral control of protein intake in rats

The availability and concentration of dietary protein was varied in an examination of the nature of the day-to-day intake of protein solutions by 60-day-old male rats. It was found that the rats consumed a remarkably constant absolute amount of protein each day, adjusting overall caloric intake to maintain protein at a roughly constant proportion of total calories. Factors such as the time of access to a protein source or the extent of prior experience with a protein source were seen to influence the overall constancy of protein intake, whereas daily shifts in preference between two available concentrations of protein did not interfere with such short-term control. The mechanism for this behavioral control is likely to be different from mechanisms mediating the conditioned response to dietary protein, as in the response to dietary amino acid imbalance.