Studies on Phosphorus Assay Techniques

A NUMBER of chick assay procedures have been devised and tested for the estimation of availability of phosphorus in various mineral supplements. Invariably the assays have indicated a relatively poor availability of phosphorus from soft phosphate, the range extending from 25% (Gillis et al, 1954) to 58% (Waldroup et al, 1965). These low values for the utilizable phosphorus of soft phosphate are in marked contrast with the relatively good growth and bone calcification of chick reported recently with this type of supplement when specific calcium: phosphorus ratios and high levels of vitamin D3 were used (Motzok et al., 1965Motzok et al., 1967; Fritz and Roberts, 1966; McKnight and Watts, 1966). The literature concerned with various aspects of phosphorus biosassay has been reviewed by Nelson and Peeler (1964), Waldroup et al. (1965) and Sullivan (1966). In many of the assay diets the calcium content has been adjusted to give either a constant level . . .