Rock Phosphates as Phosphorous Supplements for the Growing Chick

There has been considerable recent interest in the use of defluorinated rock phosphates as a source of phosphorous supplement. Observations on the use of defluorinated rock phosphate for the growing chick have been made by Bird and Caskey (1943) who concluded that the phosphorus of amorphous calcium meta phosphate is as available as that of tri-calcium phosphate; and by McConnell et al. (1944) who found fused rock phosphate to be as satisfactory as bone meal but obtained inconsistent results with calcium meta phosphate. A critical study of the data appearing in these two papers reveals that Bird and Caskey (1943) used a basal diet containing 0.42% phosphorus and supplemented it with tri-calcium phosphate or calcium meta phosphate so as to bring the phosphorus content up to 0.8% to 1.10%, while McConnell et al. (1943) obtained inconsistent results with a diet containing 0.6% phosphorus, 33.3% of which was contributed by calcium . . .