Utilization of Calcium and Phosphorus from Soft Phosphate by Chicks

MUCH of the research into the availability of phosphorus of soft rock phosphate prior to 1965 has been reviewed by Almquist (1962) and Motzok et al. (1956, 1965). Recently, McKnight and Watts (1966) reported that soft phosphate was inferior to Curacao Island phosphate and dicalcium phosphate as a source of phosphorus, but that the addition of vitamin D3 at levels above the established requirements resulted in increased growth, percent ash and efficiency of feed conversion. Increasing the level of phosphorus tended to reduce the differences between sources of phosphorus and the response to increasing levels of vitamin D3. Fritz and Roberts (1966) reported that with soft rock phosphate, normal calcification with White Rock chicks was obtained with 0.55% added phosphorus and 3,000 I.C.U. vitamin D3/kg. in a diet containing about 0.25% phosphorus from plant sources. The best results were obtained with Ca:P ratios near unity and excess calcium depressed growth …