The effect of finite periods of undernutrition at different ages on the composition and subsequent development of the rat

Abstract In continuation of the work of Widdowson & McCance (1960), previously published in the Proceedings, groups of rats growing rapidly after a high plane of nutrition during suckling were undernourished for 3 weeks so that their weights at 6, 9 and 12 weeks of age were the same as those of rats which had been growing slowly after a lower plane of nutrition during the first 3 weeks of post-natal life. The undernourished rats were then rehabilitated by being given unlimited food. Undernutrition after weaning made progressively less difference to the ability of the rats to make a complete recovery, so that, whereas a low plane of nutrition during suckling produced smaller animals at maturity, and so to a lesser extent did a low plane of nutrition from 3 to 6 weeks, undernutrition from 6 to 9 weeks did not do so. Undernutrition from 3 to 9 weeks, however, did prevent the animals attaining the same size as the controls. Although their weights might be the same at death the size and composition of rats which had grown fast and then been undernourished differed in characteristic ways from those which had grown slowly and steadily all the time. The bones were longer, the testes and stomachs were heavier, the livers, spleens, skins and small intestines were lighter. The chemical findings were in keeping with the anatomical ones.