Mechanical effects of sodium fluoride on bovine cortical bone.

Seventeen 5 to 6-month-old Holstein heifer calves were divided into three groups and fed either a control ration alone or a control ration with sufficient sodium fluoride added to furnish an additional 30 or 50 p.p.m. fluoride based on total dry matter intake. After 6 years of the feedings, mean (SEM) fluoride concentrations in the metacarpals were found to be 594.6 (66.2), 2663.8 (319.2), and 4500.0 (417.8) p.p.m. Bone mineral density and mechanical evaluations were also conducted on the harvested metacarpals after the 6-year period. Using dual energy X-ray absorptiometry, mean (SEM) bone mineral densities of 3.030 (0.26), 2.801 (0.34), and 2.456 (0.19) g cm(-2) for the control group, the group receiving 30 p.p.m. fluoride, and the group receiving 50 p.p.m. respectively were found. For the mechanical testing, specimens were cut and tested in compression parallel to the long axis of the metacarpals. Mean (SEM) ultimate stress of 204.53 (3.63), 208.83 (5.25), and 205.93 (5.12) MPa and mean (SEM) Young's elastic moduli of 20.82 (1.52), 22.68 (2.38), and 21.55 (1.60) GPa for the control, the 30 p.p.m., and the 50 p.p.m. fluoride groups respectively were determined. No significant differences were found between control and treatment groups for either mechanical properties or bone mineral density.

Effect of dietary fluoride on dairy cattle: growth of young heifers.

Thirty 5 to 6-mo-old Holstein heifer calves were divided into three groups and fed a control ration or the control ration with sufficient NaF added to furnish an additional 30 or 50 ppm F based on total dry matter intake. Fluoride content of the hay and grain was 5 and 15 ppm, respectively. The addition of 30 or 50 ppm F had no effect on growth or dry matter intake over the next 70 wk. After 1 yr on experiment, concentrations of F for animals in the control, 30, and 50 ppm F groups were 402, 2509, and 3743 ppm F in vertebral biopsies; .06, .21, and .27 ppm F in serum; and 1, 8, and 13 ppm F in urine. Fluoride ingestion had no influence on various indices of anemia, thyroid function, or on differential white cell counts, nor did it influence ration digestibility. These data suggest that young heifers can be fed up to 50 ppm of a soluble fluoride in their ration with no adverse effect.

Effects of fluoride emissions from a modern primary aluminum smelter on a local population of white-tailed deer (Odocoileus virginianus).

The influence of fluoride emissions from a modern aluminum smelter on concentrations of skeletal fluoride and dental fluorosis in a resident population of white-tailed deer was studied. The smelter was located on Mount Holly Plantation in South Carolina, and concentrations of skeletal fluoride in the deer collected at Mount Holly increased approximately five-fold 3 yr after the operation began. Increases in skeletal fluoride of less than two-fold were observed in deer obtained from Medway Plantation which has its nearest boundary 1.6 km from the smelter site. No dental fluorosis was observed in deer collected at Medway Plantation, but mild dental fluorosis was observed in a significant number of deer collected at Mount Holly Plantation. The dental fluorosis that was observed was not associated with incisor wear or with fluoride-induced molar wear. Osteofluorosis of mandibles or metacarpals was not observed in any of the deer obtained from either plantation. The data obtained from this study indicated that the presence of a modern aluminum smelter caused a detectable increase in concentration of skeletal fluoride in the resident population of white-tailed deer, but that no adverse health effects were seen.

The availability of fluoride from NaF and phosphorus supplements.

The availability of fluoride (F) from dicalcium phosphate (DCP), defluorinated phosphate (DFP), and raw rock phosphate (RRP) has been assessed and compared to the availability of F as NaF. Diets containing 50-55 ppm F were fed to lambs and rats and skeletal F retention determined. The relative availability of F in the different phosphate sources measured by this technique compared to that of NaF was about 50% (DCP), 20% (DFP), and 65% (RRP). Digestibility of F in goats fed similar diets was determined in a 4 x 4 Latin Square design experiment and found to be 38% (DCP), 34% (DFP), 65% (RRP), and 75% (NaF).

Dental fluorosis in bovine temporary teeth.

Deciduous incisors from calves born to dams fed an average of 40 mg of fluoride/kg of forage ration (40 ppm) were compared with incisors from calves born to dams fed a normal dairy ration. Skeletal fluoride concentration in the calves born to fluoride-fed dams was increased 5 to 8 fold, but enamel mottling and hypoplasia, typical of permanent bovine incisor dental fluorosis were not seen by gross, histologic, or radiologic examination. Decreases in the amount of enamel on the tooth or hardness of the enamel were not observed. These data do not support recent reports of widespread dental fluorosis of deciduous bovine teeth as a clinical sign of fluoride toxicity.