Gastrointestinal absorption, tissue distribution, and excretion of 95Nb in newborn and weanling swine and sheep

Carrier-free 95Nb in oxalic acid was administered orally by intubation or intravenously (iv) to sheep and swine 6-18 hr after birth or 3 weeks after weaning. Animals were sacrificed 3 days later and the 95Nb contents of several internal organs, gastrointestinal (GI) contents, and excreta examined. Considerably more 95Nb was absorbed by animals receiving 95Nb orally between 6 and 18 hr after birth (18 to 50 percent of administered dose) than by those receiving it after weaning (0.06 to 0.5 percent). The skeleton and GI tissues of iv-injected neonates contained more 95Nb than iv-injected weanlings, but no differences were observed in total-body 95Nb. While almost all the 95Nb remaining in the digestive tract contents of swine (both age groups) and suckling sheep was present in the ileum and large intestine, as much as one-third was still in the four-compartment stomach of weaned sheep 3 days after oral administration