The Effects of Deficiency of Phosphorus on the Utilization of Food Energy and Protein

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Abstract
The effects of phosphorus deficiency on the growing rat were studied in two 70-day body balance and metabolism experiments conducted with paired feed control. In the first experiment the phosphorus deficient and the phosphorus supplemented diets contained 0.137% and 0.366% of phosphorus, respectively, on the dry matter basis; and after two groups of rats had consumed these diets for 70 days the corresponding average phosphorus contents of their bodies were 0.94% and 1.08%, respectively, the difference between these values being 15% of the lower one. In the second experiment the low and the high phosphorus diets contained 0.133% and 0.653% of phosphorus, respectively; and after 70 days' feeding on these diets the corresponding average phosphorus contents of the rats' bodies were 0.98% and 1.16%, respectively, the difference between these values being 18% of the lower one. In the first experiment, the difference in dietary phosphorus intake which produced a 15% difference in body phosphorus produced no observed difference in growth or in the utilization of food energy or protein. In the second experiment, the difference in phosphorus intake which produced an 18% difference in body phosphorus produced a slight but statistically significant depression in the digestibility of food protein. This was the effect of the disodium phosphate of the high-phosphorus diet. In this second experiment there were no other observed effects of the difference in phosphorus intake on the utilization of food energy or protein, or on growth. The phosphorus content of the low phosphorus diet was as low as the experimenters could make it and at the same time have sufficient feed consumption and growth to serve the purposes of the investigation. Normal growth could not have been obtained on a diet still lower in phosphorus.