Ruminant Utilization of Inorganic Phosphates

Abstract

Steers and lambs were used to ascertain the relative availability of various inorganic phosphatic materials for ruminants, using phosphorus balance and inorganic blood phosphorus levels as criteria. Yearling steers, which had received rations low in phosphorus for 4 months, were fed approximately 1.70 or 1.00 gm. of phosphorus per 100 weight daily in successive experiments, of which 50% in the first experiment and 66% in the second experiment was supplied by inorganic phosphatic material. Weanling lambs were depleted of phosphorus stores by feeding a semi-purified ration containing about 0.03% organic phosphate. Following depletion, the lambs were fed experimental rations containing 0.13 to 0.16% phosphorus of which almost 80% came from the inorganic sources. Two commercial, electrothermally produced, dicalcium phosphates, two calcined defluorinated phosphates, and one sample each of bone meal, soft phosphate with colloidal clay, and Curacao Island phosphate were of equal value in promoting phosphorus retention and maintaining blood phosphorus levels in yearling steers. Of the 4 commercial phosphate samples tested with lambs, dicalcium phosphate and Curacao Island phosphate were well utilized but soft phosphate and a calcined defluorinated phosphate were poorly utilized. Gamma calcium pyrophosphate was essentially unavailable to lambs. Vitreous calcium metaphosphate was utilized to some extent but significantly less so than was the orthophosphate (monocalcium phosphate).