Maternal and fetal selenium concentrations and their interrelationships in dairy cattle

Paired dam-fetus serum, whole blood and liver samples were collected from 101 pregnant dairy cattle at slaughter to establish mean values for fetal tissue selenium concentration and to determine relationships between maternal and fetal selenium status. Samples were assayed for selenium concentration in serum, whole blood and liver and for whole blood glutathione peroxidase (GSH-Px) activity. Fetal age was estimated from fetal crown-to-rump length. Mean fetal liver (2.14 micrograms/g dry wt) and serum (21.4 ng/ml) selenium concentrations and whole blood GSH-Px activity (21.6 mu/ml) differed (P less than 0.0001, 0.0001 and 0.01, respectively) from corresponding maternal values (0.95 micrograms/g liver dry wt; 44.0 ng/ml; 16.7 mu/ml, respectively), while no differences were found between whole blood or erythrocyte selenium concentrations. Fetal liver selenium concentration was greater than corresponding maternal liver selenium in 99% (96/97) of the dam-fetal pairs, suggesting efficient placental transfer and fetal concentrating ability. Maternal liver selenium concentration was most highly correlated to all fetal tissue selenium concentrations and used to develop prediction models. These data suggest that selenium efficiently passes the placenta, and based on published values of adequate adult liver selenium concentrations and maternal-fetal relationships, we suggest an adequate liver selenium concentration in the bovine fetus to be greater than 2.2 micrograms/g liver dry wt, and in whole blood, greater than 120 ng/ml.