Placental transfer of fluoride in Holstein cows.

Placental transfer of fluoride was studied in 40 Holstein cows and related to a previous 7 1/2 y study for comparative purposes. Animals were randomly assigned to fluoride dosage groups of control, 0.51, 1.31 or 2.66 sodium fluoride/d (10, 25, 50 or 100 ug/g feed). Each animal received the dose daily via gelatin bolus for 4-14 d prior to parturition. Maternal heparinized blood samples were collected before dosing and after parturition. Placental cotyledon and calf blood samples were collected from each animal immediately after parturition. Maternal and calf plasma and placental cotyledon fluorine concentrations were determined. Increased levels of fluoride given to pregnant cows resulted in significantly increased (p less than 0.05) maternal plasma and placental cotyledon fluorine concentrations. Calf plasma fluorine concentrations at birth did not significantly increase in relation to the fluoride treatment level of dams. The data support the concept that under normal circumstances in cattle there is a partial placental barrier to fluoride that operates to limit fluoride concentrations in the fetal circulation and tissues.