Fasting Catabolism and Food Utilization of Calcium-deficient Rats

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Abstract
Rats were fed a diet containing only 10 mg. calcium per 100 gm. of food. After 2 months, their mean body weight was approximately 30% below the body weight of litter mate controls fed ad libitum on the same diet, but with added calcium. A considerable decrease in appetite on the calcium-deficient diet is mainly responsible for the retarded growth. The body weight of calcium-supplied control rats could be kept equal to that of their calcium-deficient pair mates by restricting their food intake through paired feeding to a level slightly, but significantly, below that of the calcium-deficient rats. The calcium-deficient rats were shorter, with a smaller skull, and a finer skeleton than their pair-fed controls. The liver dry weight of the deficient rats was significantly higher than that of the controls. The carcasses of the deficient rats contained only one-half as much ash, and only one-third as much calcium, as that of the calcium-supplied controls. The calcium concentration of the blood serum of the deficient rats was reduced to one-half that of the controls. The calcium-deficient rats were less active than the controls. The rate of fasting catabolism per unit of 3/4 power of body weight of the calcium-deficient rats, kept in an environment of 30°C. for 18 hours before, as well as during, the respiration trials, was consistently higher for the calcium-deficient rats than for their calcium-supplied controls. This result was obtained with two groups of rats all of which were fed ad libitum, in which case the calcium-deficient rats had a considerably smaller body weight than their calcium-supplied litter mate controls. The increase of metabolic rate resulting from calcium deficiency was confirmed by a third group of rats in which the pair mates were kept equal in body weight by restricting the food intake of the calcium-supplied controls. In the pair-fed group, the difference in the metabolic rate between calcium-deficient and calcium-supplied rats seemed to increase as the deficiency became more severe. The metabolic rate of the deficient rats in three successive series of trials was 116 ± 3, 122 ± 3, and 132 ± 4% of the corresponding rats of the controls. The total efficiency of utilization of food energy was decreased by calcium deficiency, not only by a lowering of the food intake and by a higher basal metabolism, but also by a lower partial efficiency. This may mean a greater loss of unoxidized material in feces and urine, or a higher calorigenic action.