21 C.F.R. § 573.200
(b) Specifications. The additive shall conform to the following percent-by-weight specifications:
Moisture, not less than 45 percent nor more than 50 percent. Protein, not less than 24 percent. Salt (NaCl), not more than 15 percent. Phosphorus, not less than 2.25 percent.
(c) Uses. It is used or intended for use as a source of animal protein, phosphorus, and salt (NaCl) as follows:
(d) Labeling. The label and labeling shall bear, in addition to the other information required by the act: