Metabolism of Radioactive Cesium (>34Csand lî7Cs) and Potassium by Dairy Cattle as Influenced by High and Low Forage Diets '•*

ABSTRACT A feeding trial was conducted with 10 lactating Holstein cows to de termine the excretion patterns of fallout 137Csand potassium in milk, urine and feces as affected by a high hay (80 % ) or high grain (80 % ) ration. It was found that 13TCs was excreted principally via the fèces as compared with potassium which was largely excreted in the urine. Tracer doses of soluble 134Cswere transferred to milk and urine to a greater extent than fallout 137Cs. A marked decrease in absorption was noted when the dose was administered with a high hay ration as compared with a high grain ration, which was apparently due to adsorption by fibrous components of the ration. The mean transfer coefficients of fallout 137Csto milk (pCi per liter/total daily intake in pCi) were 0.48 for the high hay and 1.21 for the high grain ration. Tracer doses of 134Cs showed transfer coefficients of 0.92 and 1.36 when added to the same rations. Differences in absorption of potassium and 137Csas judged by transfer to milk and urine could be explained on the basis of a lower absorption of U7Cs due to its physical form in fallout contaminated forages. Previous work in this laboratory ind