Studies on fluorosis of sheep. II. The toxicity of water-borne fluoride for mature grazing sheep.

Abstract

Three groups each of 16 mature sheep were allowed to graze on sown pasture for 26 months. One group was given reservoir water, containing approximately 0.3 p.p.m. F, to drink, but the other two groups were offered similar water to which had been added sufficient sodium fluoride to give final concentrations of 10 or 20 p.p.m. F. During the winter months the treated groups drank only 0.5 1. or less of water per day and ingested virtually no fluoride. During the summer months the daily consumption of water by the groups which received 10 and 20 p.p.m. F rose to between 3 and 4 l., and the daily intake of fluoride, expressed as fluorine, to approximately 30 and 60 mg F respectively, equivalent to 0.4 and 0.8 mg F per kg body weight. The overall mean daily intakes of fluoride for the whole experiment by the two groups were 18 and 33 mg F or 0.24 and 0.44 mg F per kg body weight respectively. The ingestion of the amounts of fluoride supplied by drinking water containing as much as 20 p.p.m. F appeared to have no adverse effect on general health, body weight, or wool production of mature sheep over a period of 26 months. A brown deposit was present on the incisor teeth of all sheep throughout the experiment but was more pronounced during periods when the pasture was green; it did not appear to be related to fluoride intake, for it was as severe among the control sheep as among the treated ones. No mottling of the incisors or molars was observed, nor was there any evidence of excessive or uneven wear on these teeth. Ingestion of fluoride brought about increases up to threefold in the fluoride content of the bones and teeth.