Manganese Utilization and Placental Transfer in the Gravid Gilt

Fifteen yearling sows and 73 third trimester fetuses were used to study tissue-organ distribution and movement of stable Mn and retained 54Mn across placental membranes. Sows consuming 87 mg Mn per day excreted 62 mg and absorbed 28% of the daily intake. After 7 days 26% of the oral and 78% of the IV 54Mn dose was retained. 54Mn clearance by kidneys was greatest 45 to 60 min. post-dosing, averaging 0.72 ml urine per minute and 0.3 mg Mn per day. Blood 54Mn disappearance was rapid, and after 5 min. only 25% of the injected dose remained in total blood. Liver served as a principal metabolic pool, reaching maximum 54Mn concentration 6 hr. post-dosing. Pregnancy had no significant effect upon maternal tissue retention, organ distribution or turnover rate. Fetal mass appeared to be a major factor affecting total Mn transfer. Third trimester litters contained 6.4 mg Mn; placenta, 1.4 mg, and total placental fluids 0.6 milligrams. After 168 hr., 25.7% of the retained 54Mn was transferred to the conception products, 87% of which was in the developing 110-day old fetuses.