Response of young rats to rehabilitation with diets containing different amounts of protein after deprivation of protein or of calories

Protein deficiency in young children remains one of the major dietary problems of the world.Waterlow, Cravioto & Stephen (1960) reviewed the subject from many points of view, and they summarized what is known about the metabolic effects of protein deficiency on children and the animal experiments which they and other workers have made to study the effects of protein deficiency on metabolism.Widdowson & McCance (1957) analysed the bodies and the livers and skeletal muscle of young rats that had been fed on a diet very low in protein, or on a diet high in protein but limited in quantity to maintain the animals at the same weight as those on the lowprotein diet.Well-fed control animals were also analysed, and the effects of rehabilitation were studied.This investigation left several questions unanswered, and no work since that time has entirely solved the problems that were raised.The investigation now described was planned to answer two questions: (u) Why did the young animals fed on a high-protein diet in strictly limited amounts die sooner than those on a low-protein diet, although the loss of body-weight in the two groups was the same?(b) What is the effect of the two diets on the distribution of nitrogen and other constituents in the body?A preliminary account of this aspect of the results has already been published (Dickerson & Cabak, 1962). METHODS Experimental designSixty male rats were used.They were about 5 weeks old when the experiment began, and their mean weight was 87 g.Six animals were killed on the 1st day of the experiment and their bodies analysed as described below.Eighteen animals were fed on a low-protein diet in unlimited amounts.T h e diet was that described by Widdowson & McCance (1957) and consisted of cassava flour and fresh banana.Eighteen animals were given a high-protein diet consisting of equal parts of full-cream dried milk and fish meal in limited amounts, so that the mean body-weight was kept as close as possible to that of the animals on the low-protein diet.The animals in this group were housed in individual cages.A third group of eighteen animals was fed ad lib. on a mixture of the low-and high-protein diets (see below) and these rats served as well-nourished age controls.After 26 days, six rats in each group were killed, dissected and analysed as described below.T h e remaining animals were used for a study of the effects of rehabilitation (Cabak, Dickerson & Stanier, 1963).