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.