Protein and calorie malnutrition in infant cebus monkeys: growth and behavioral development during deprivation and rehabilitation.

The growth and development of 32 cebus monkeys were studied during a period of insult in nutritional or rearing conditions and after rehabilitation. Eight experimental groups of four animals each were subjected to one of four diets--control, protein restricted, calorie restricted, and protein-calorie restricted, and one of two rearing conditions-partial isolation or a comparatively enriched condition-in a 4 x 2 factorial design. The period of insult from 2 to 6 months of age was followed by 6 months of rehabilitation in both diet and rearing conditions. It was found that only diet affected physical growth, but both diet and rearing affected behavioral development and exploratory behavior. Whereas calorie deficiency produced a direct effect on behavior independent of rearing conditions, protein deficiency produced an effect only in combination with rearing restriction. The effect of protein-calorie deficiency had some characteristics in common with each of the other deficiencies. Retardation in rate of behavioral development was less severe than retardation in growth, most notably in the protein-restricted, enriched-rearing group, producing animals who were behaviorally mature for their size. All groups caught up in physical growth during rehabilitation but the protein-calorie restricted groups failed to recuperate completely in exploratory behavior.