Hoarding behaviour and the defence of body weight in adult rats, following undernutrition during different periods of early development

In Experiment I, male rats, previously undernourished by underfeeding their mothers during lactation, weighed less as adults than progeny of mothers underfed during gestation, or than normally-nourished control rats. Daily 16 h food deprivation of the adults induced weight loss and elicited hoarding of food pellets. Deprivation-induced weight losses at criterion for hoarding did not differ significantly among the groups, and the critical weight at which hoarding began was thus significantly lower in the lactationally-undernourished group than in the controls. Thus adult rats, previously undernourished during their suckling period, appear to defend their body weights in a manner similar to controls, although at a lower level. Lactationally-undernourished rats also hoarded significantly fewer pellets than controls. Similar results were obtained when the rats were partially satiated before hoarding tests, suggesting that hoarding scores were unlikely to have been significantly affected by competition with feeding. Foetal undernutrition had weaker, and less consistent effects than lactational undernutrition on the ad libitum weight of the adult, and on the critical weight for hoarding. In Experiment II, severe undernutrition after weaning did not affect adult body weight, the weight loss necessary to induce hoarding, or the number of pellets hoarded. It is concluded that the pre-weaning period is specifically sensitive to the effects of undernutrition on body weight regulation and on hoarding. The data on hoarding do not support the view that a period of undernutrition at any time in early life increases the rat's responsiveness towards food.