Influence of Varying Calcium Levels on the Utilization of Calcium Meta- and Pyrophosphate in Chick Diets

THE wide variety of commercially availble phosphorus supplements which frequently change in analysis and availability require constant research effort in order to provide accurate information for formulation purposes. Many factors have been shown to influence the biological availability of these materials. Gillis et al. (1948) indicated that availability differences were largely due to variations in the content of metaphosphate and pyrophosphate. These compounds are primarily calcium metaphosphate and calcium pyrophosphate which the product contains naturally or which is produced by the heat of defluorination. Both of these compounds also have several different enantiotropic forms (mirror image isomers), and calcium metaphosphate has an additional vitreous form. Grau and Zweigart (1953) cited a personal communication indicating that only 36 to 60 percent of the phosphorus in phosphatic clays was available to the chick due to the significant amounts of pyrophosphate and metaphosphate forms present. Gillis et al. (1948) found the alpha, beta…