Uptake of fluoride in cattle in the lower Tamar valley

The aim of this study was to investigate the possible impact of fluoride emissions from an aluminium smelter on beef cattle on a nearby property. However, it was not possible to successfully achieve this aim. Instead, all mechanisms of fluoride uptake on the farms studied, including emissions from the smelter, were examined in relation to the condition of cattle on the properties. Ambient air monitoring demonstrated that fluorides, both gaseous and particulate, were generally low at all stations on the study property. The Washington State Standards were exceeded at two of the three monitoring stations early in the monitoring program but were below detection level for much of the later period of the study. Elevated levels of gaseous and particulate fluoride recorded at individual stations did not necessarily correlate. Pasture fluoride was the major source of fluoride for stock and levels varied over a wide range. Many of the very elevated pasture fluoride levels were associated with periods of fertilizer application. Normal fertilizer application practices on the control farm, remote from the smelter, elevated pasture fluoride levels sufficiently for the Washington State Fluoride in Forage Standard to be exceeded. The main study property was marked by low pasture availability, poor pasture cover and heavy grazing for much of the study period. Water was not a significant source of fluoride for the stock. Bone fluoride levels of the cattle on the study farm were elevated relative to those on the control farm. The rate of increase of these levels tended to decrease with age and appeared to be influenced by specific farm management practices. Many of the cattle on the study farm showed tooth damage and loss. This damage was more excessive than would have been expected, given the bone fluoride levels, and indicates that the cattle have been exposed to variable levels of fluoride. Bone fluoride levels and the development of teeth defects have been complicated by agistment of some stock during the period critical for the development of the first permanent teeth. They have also been complicated by other factors including the variations in feed availability across the property and the variability of exposure to fertilizer. Fertilizer application was found to affect both the teeth condition and bone fluoride levels of exposed cattle. A 30% reduction in smelter output during the course of the study did not significantly reduce the rate of increase of the bone fluoride levels in young cattle. Trace element supplementation of calves, distributed over a number of farms, did not produce the same levels of weight gain over all properties, reflecting apparent variations in trace element availability on the farms. Farm management practices, in particular high stocking rates and heavy grazing combined with poor pasture cover, resulted in reduced feed intake and poor condition of the cattle. Low pregnancy rates in some cattle were a result of their poor condition, not fluoride intake. Removal of these cattle to properties with better grazing conditions resulted in remarkable improvements in condition and improved pregnancy rates.