Studies on fluorosis of sheep. 1. The toxicity of water-borne fluoride for sheep maintained in pens

Abstract

Five groups, each of six sheep, were fed in pens on an adequate diet of chaffed hay and crushed grain for 3½ years. One group was given rain-water to drink, whereas the others were offered similar water to which sufficient sodium fluoride had been added to give final concentrations of 2.5, 5, 10, or 20 p.p.m. F. The mean daily intakes of fluoride, expressed as fluorine, by the four experimental groups were approximately 5, 9, 18, and 37 mg. F respectively during the winter months and 7, 13, 27, and 53 mg. F respectively during the summer months. The ingestion of fluoride appeared to have no adverse effect on general health, food consumption, or wool production. The mean weights of all groups were approximately the same throughout the experiment except at the end of 2½ years, when the weight of the group which received water containing 20 p.p.m. F was significantly less, but only at the 5 per cent. level, than that of either the control group or the groups receiving the lowest two intakes of fluoride. Mottling of the incisors and molars was only slight among the sheep which received water containing 5 p.p.m. F. It was more evident in the 10-p.p.m. group and was marked in the 20-p.p.m. group. Selective abrasion of the molars was pronounced in this last group but was also noticeable in the 10-p.p.m. group. Fluoride intake caused the incisors to erupt at an earlier age. Ingestion of fluoride brought about increases of up to twentyfold in the fluoride content of the bones and teeth. The bearing of these results on enzootic dental fluorosis among grazing sheep in Queensland is discussed.