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Fasting Catabolism and Food Utilization of Magnesium Deficient Rats

One Figure

Division of Animal Husbandry, University of California, College of Agriculture, Davis, and the Division of Biochemistry, University of California Medical School, Berkeley

1. Five rats fed a magnesium deficient diet gradually lost appetite and, after 60 days on this regime, ceased to grow. Littermate controls could be kept at the same weight as the deficient rats by restricting their intake of magnesium-supplied food to 83% of the consumption of the deficient rats.

2. The magnesium content of the carcasses of the deficient rats was only one-half of that in the control rats, but there was no significant difference between the water, ash, fat, and protein content of magnesium deficient and control rats.

3. Body length was not affected by magnesium deficiency. The dry weights of the heart and liver were slightly greater, and those of the thyroid and adrenal glands significantly greater in the magnesium deficient animals than in their magnesium supplied controls.

4. The rate of fasting catabolism of the magnesium deficient rats progressively increased in comparison to the rate of the magnesium supplied controls. The catabolic rate of the deficient rats amounted to 125% of the rate of the controls, 57 days after the pairing of the rats.

5. Magnesium deficiency decreased the efficiency of energy and protein utilization to approximately the same extent, causing an extra waste of 18% of the intake. The increased rate of fasting catabolism is not sufficient to explain the extra waste of energy by the magnesium deficient rats. It can therefore be concluded that magnesium deficiency causes an increased loss of unoxidized material in the excreta, or increases the calorigenic action of the food.