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The Availability of the Calcium and Phosphorus of Defluorinated Rock Phosphate for the Rat

Two Figures

Laboratory of Animal Nutrition, Cornell University, Ithaca, New York

A basal diet low in both calcium and phosphorus has been employed to study the availability of three defluorinated rock phosphates for bone formation in the rat. The rock phosphates have been studied at levels of from approximately 0.7 to 7.0% of the diet. These levels gave diets containing from 0.15% phosphorus and 0.24% calcium to 1.00% phosphorus and about 2.0% calcium.

Product no. 1, a defluorinated superphosphate, was significantly less efficient for bone formation than calcium phosphate or bone meal. Product no. 1 inhibited the growth of rats, and this became more apparent as the level was raised.

Product no. 2, a defluorinated superphosphate, was less available for bone formation than calcium phosphate at low levels. However, when it was supplemented at approximately twice the level of calcium phosphate, equal bone formation resulted.

Product no. 3, a fused rock phosphate, was slightly less efficient than calcium phosphate at very low levels. When the diet was supplemented with this fused, defluorinated product to contain 0.50% phosphorus or more, however, product no. 3 was equally as satisfactory as calcium phosphate for bone formation.

It is suggested that the low availability of the defluorinated superphosphates, products 1 and 2, may be due to the presence of relatively large amounts of the poorly utilized calcium metaphosphate.

While these results may not apply to farm animals they suggest the importance of giving attention to procedures used in manufacturing defluorinated rock phosphates and of testing these products with farm animals.