Uranium and radium in livestock feed supplements

Uranium (2 to 180 ppm) is present in livestock feed supplements in proportion to their phosphorus contents. This is apparently due to the transfer of uranium with phosphorus from the original mineral phosphate (rock phosphate) to the feed, regardless of whether the mineral has been chemically processed or used more or less directly. However, feed supplements fall into two groups with respect to 226Ra: one in which radium is approximately 70% of the equilibrium amount, and one in which the radium is only about 6% of the equilibrium amount. This difference is a function of the type of phosphate material used in the supplement. Calculations indicate that neither the uranium nor the radium in livestock feed supplements is hazardous to human beings, assuming it is valid to utilize the results of the studies cited in estimating the ingestion and transfer of these isotopes via feeds. (author)