Ingestion of soil fluorine: Its impact on the fluorine metabolism and status of grazing young sheep

Abstract

When young sheep ingested soil fluorine (F) at moderate to high rates (69–184 mg F day⁻¹ for 63 days) the apparent absorption of F ranged from 44 to 53%, while apparent retention of F ranged from 28 to 42%. The respective values for ingestion of sodium fluoride (NaF) at 69 mg F day⁻¹ were 69% and 39–45%. Increasing F intakes had little effect on kidney and liver F concentrations, but markedly increased the bone F concentrations in the sheep fed NaF or soil with high levels of F. Further, serum F concentration and the rate of F accumulation in bone were related to soil F intake. The rate of F accumulation in bone was curvilinearly related to serum F concentration, and serum F concentration had to be > 0.25 mg litre⁻¹ before a significant accumulation of F occurred in bone. Serum F concentration could be a useful index to assess the soil F intakes and F status of grazing sheep. An examination of the sheep during and at the end of the study showed no clinical signs of fluorosis, such as mottled teeth or bone abnormalities.

Keywords:

• sheep
• fluorine
• soil F intake
• serum F
• bone F