Placental transfer and maternal-fetal utilization of manganese and copper by swine and sheep

Both manganese and copper have been shown to be necessary for the normal functioning of the animal body, and although there is a vast quantity of information available from laboratory animals, little or no factual information is readily available on placental transfer or maternal-fetal utilization of these two minerals. For these reasons this study, utilizing 15 yearling gilts (73 fetuses) and 15 yearling ewes (13 fetuses), was initiated during the spring of 1968. Pregnant gilts and ewes were dosed with a single tracer level of radiomanganese and radiocopper for blood balance and subsequent tissue-organ distribution and placental transfer studies. Results indicated that, within species, stage of pregnancy did not influence blood disappearance rate, tissue-organ distribution or excretion of manganese and copper. Species did influence fecal excretion of manganese, with sheep retaining approximately one-fourth the intravenously injected manganese as did swine. Amount and rate of manganese transfer was also influenced by species. During the third trimester and at 168 hr. post-dose administration, an 8,000 gm. swine litter contained 22.8 percent of the intravenously injected ⁵⁴Mn; while a 5,000 gm. lamb fetus contained 3.0 percent. Fetal weight within species was the main factor in determining total percent ⁵⁴Mn transfer. However, 24 hr. post-dosing, an 8,000 gm. swine litter contained 2.4 percent and a 5,000 gm. lamb fetus contained 2.2 percent of the ⁶⁴Cu dose, indicating that fetal weight, rather than species, influenced the total percent transferred. Total fetal analysis indicated that radiomanganese transferred during the 168 hr. time study was in relation to manganese content, but this relationship was not reached for radio-copper and copper by 24 hr. post-dosing. Many factors have been shown to influence placental transfer, and this study further indicated that numerous interrelated factors contribute to the determination of what passes from dam to fetus.