ous related to the oral dose for calves. It concerned the original intraven um dose to adult cows that would eventually result in the appropriate plutoni concentration per gram of milk. It should be noted that there are normal the variations in daily milk production which can apparently alter either um plutoni of amount total the or milk of gram per plutonium concentration transferred to milk per collection. Furthermore, while the daily milk produc- tion of adult Holstein cows often approximates 20 liters, an individual 10-day- old calf will ingest only 2 to 4 liters of this milk per day. Table 1 presents some background information on the animals and the plutonium doses administered during the feasibility study. As stated above, all intravenous doses to the lactating cows were given as citrate-buffered plutonium-238 The first adult cow received a single 83 mCi injection. nitrate injections. Milk, urine, and fecal samples were taken for 72 hours after injection, but no tissue samples were collected at time of sacrifice 90 hours post-dosing. second adult cow received an initial injection of 9.95 mCi following which The As noted in Table 1, three milk, urine, and fecal samples were collected. ly administered to this animal sequential additional plutonium injections were 144 hours after the initial beginning e (one per day for three consecutiv days) dose. The im vivo plutonium-labeled milk collected following these sequential injec- tions was fed to two calves. Background information on these calves is also The second adult cow was sacrificed approximately 13 presented in Table 1. days after the initial dose, but no tissues were collected. The calves ingested plutonium-labeled milk for 6 days. For 2 days after the last treatment feeding, the calves were given uncontaminated milk from the dairy herd. All calves were then sacrificed, including two control calves that had received uncontaminated milk throughout the study. Calf tissues were taken at sacrifice and included samples of liver, lung, bone (femur-diaphysis and epiphysis, sternum and marrow), gall bladder and bile, gonads, duodenum (mucosa and serosa), spleen, muscle (skeletal and cardiac), lymph nodes, thymus, adrenals, thyroid, abomasum, omasum, reticulum, rumen, and blood. Phase II Information gained during the feasibility study was applied to the design of a definitive effort (Phase II). This Phase II program has recently been conducted and will thus be briefly summarized. this portion of the project. Tables 2 and 3 provide an outline for Four adult cows were given a single intravenous injection of citrate-buffered plutonium-238 nitrate (approximately 16.6 mCi per animal). Plutonium-labeled milk from these cows, collected during the period of peak concentration, was fed to four calves. Four additional calves . received in vittro plutonium-labeled milk prepared with approximately the same plutonium concentration as in the im vivo labeled milk. Each group of calves contained two control animals which were sacrificed along with the experimental calves. Tissues were collected from 11 of the 12 calves for plutonium analysis. Furthermore, for the Phase II effort, tissues were taken from the adult cows and analyzed for plutonium content. Additional details of this second phase experiment will be presented, along with the analytical results, in-a subsequent comprehensive report. , 181