Abstract
An in vitro and in vivo experiment was performed to determine the extent of movement of samarium (Sm), cerium (Ce), and lanthanum (La) from the original feedstuff upon which they were adsorbed to other feed particles. The rare-earth elements were demonstrated to be tenaciously bound to the particulate phase, with essentially none of the element occuring in the liquid phase. When Sm, Ce and La were adsorbed onto grain, 92.6% of the elements remained with the grain after a 24 hr incubation period in vitro. When Sm, Ce and La were adsorbed onto hay, 99.2% of the elements remained associated with the hay after a 24 hr incubation period. Four rumen fistulated cows were fed Sm, Ce and La treated hay (1 g of element applied per .9 kg of hay) for 5 days. At the beginning of the sixth day, unmarked hay was fed and removed from the rumen every 6 hr for 24 hours. At 6, 12, 18 and 24 hr, 4.4, 5.8, 5.9 and 10.1% of the rare-earth elements on a ppm basis were detected on particulate fractions other than the one upon which they were originally placed. Possible reasons for the small amount of marker movement are discussed. Rare-earth elements can be used as multiple or simultaneous markers of ration ingredients as they pass through the digestive tract. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.