Phosphatic Clay as a Phosphorus Source for Chicks

AMONG the sources of phosphorus available for poultry feeding is phosphatic clay, which is also called soft phosphate with colloidal clay. Representative samples of this product contain about 8.5 percent phosphorus, 18 percent calcium and 1.2 percent fluorine. Gerry, Carrick, Roberts and Hauge (1947) found that 2.5 percent phosphatic clay produced a satisfactory calcification in young chicks, but the rate of growth of groups fed phosphatic clay was lower than with groups fed equivalent amounts of bone meal, an effect attributed to the fluorine contained in phosphatic clay. Miller and Joukovsky (1953) compared phosphatic clay with Curaçao Island rock phosphate, defluorinated rock phosphate, dicalcium phosphate and bone meal at calcium-phosphorus ratios of 2:1 when the supplement provided 0.2 percent or 0.4 percent phosphorus. They estimated that somewhat less than half of the phosphorus of phosphatic clay is available, as compared with the other sources tested. At the higher phosphorus level, …