Transfer and distribution of radioactive cadmium in dairy cows

The metabolism of radioactive cadmium was studied in lactating cows. Faecal excretion, secretion in milk and urinary excretion were followed after (a) a single oral application of ^115mCdCl₂ (b) a repeated oral application for 10 days of ^115mCdCl₂ (c) an intravenous injection of ^115mCdCl₂ (d) an oral administration of ¹⁰⁹CdCl₂ directly, and (e) oral administration of ¹⁰⁹CdCl₂ absorbed in maize leaves. Intestinal absorption was found to be two percent of the dose or less. Secretion into milk was small, and an approximate estimate for the transfer coefficient in milk of 1 x 10^-4 -1 x 10^-3 days/1 was made. Cows sacrificed 131 days after oral application of ¹⁰⁹Cd contained about 0.13 percent of the initial dose but only 0.025 percent after administration of maize. About 50 percent of the activity was found in liver and 20 percent in kidney. A tentative estimate of the transfer coefficient for liver yielded 0.02-0.2 days/kg for meat 1 x 10^-4 -l x 10^-3 days/kg.