Postnatal Nutritional Deprivations as Determinants of Adult Rat Behavior toward Food, Its Consumption and Utilization

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Abstract
During the first 7 weeks of life, rats were subjected either to restriction of the quantity of diet of optimal composition or to protein-deficiency malnutrition to learn more about the animals' behavior toward food several months following complete nutritional rehabilitation. The day following parturition female rats were fed a low protein diet (12% casein) for the duration of the nursing period (3 weeks). This resulted in a decreased milk supply and a consequent retardation in the growth of the pups. At weaning, some of the restricted pups were fed for 4 weeks a severely protein-deficient diet (5% casein) which prevented any weight gain during this period (designated low protein). Others were given a diet of optimal composition but in restricted amount so they did not grow during the 4-week experimental period (designated restricted). All animals were then given the normal control diet ad libitum. When adult weight had been reached (6 months of age), the previously low protein and restricted rats were smaller than the controls. Expressed on the basis of body weight0.75, food intake was significantly greater in the previously low protein rats. It is believed this may be accounted for by altered body composition, with a larger percentage of metabolically active tissue in the previously low protein rats. When food spillage was measured in rats fed ad libitum, there was no difference between controls and previously restricted or low protein rats. However, when food availability was limited to 1 hour each day, there was a threefold increase in food spillage in previously low protein, male rats and a significant but much smaller increase in previously restricted, male rats as compared with controls. No difference in food consumption or food spillage was observed in female rats. The food spillage of previously malnourished rats is believed to be one of several manifestations of elevated excitement under stress that have been noted in other studies with adult animals that were severely malnourished in early life. The present studies also confirm and extend previous observations from our laboratories which conclusively show that postnatal nutritional stunting of adult body size is not necessarily correlated with behavioral development. Behavioral abnormalities in the adult that are due to postnatal nutritional deprivations, however, always appear to be accompanied by a stunting of body size. Nitrogen balance studies with both casein and wheat gluten showed no effect of early postnatal malnutrition on nitrogen retention in the adult.