Gastrointestinal Absorption, Tissue Distribution, and Excretion of <tex-math>${}^{95}{\rm Nb}$</tex-math> in Newborn and Weanling Swine and Sheep

Carrier-free <tex-math>${}^{95}{\rm Nb}$</tex-math> 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 <tex-math>${}^{95}{\rm Nb}$</tex-math> contents of several internal organs, gastrointestinal (GI) contents, and excreta examined. Considerably more <tex-math>${}^{95}{\rm Nb}$</tex-math> was absorbed by animals receiving <tex-math>${}^{95}{\rm Nb}$</tex-math> orally between 6 and 18 hr after birth (18 to 50% of administered dose) than by those receiving it after weaning (0.06 to 0.5%). The skeleton and GI tissues of iv-injected neonates contained more <tex-math>${}^{95}{\rm Nb}$</tex-math> than iv-injected weanlings, but no differences were observed in total-body <tex-math>${}^{95}{\rm Nb}$</tex-math>. While almost all the <tex-math>${}^{95}{\rm Nb}$</tex-math> 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.