Effects of Alternating Periods of High- and Low-Fluoride Ingestion on Dairy Cattle

Abstract

Two- and five-month old Holstein heifers were exposed to different intake patterns of dietary fluoride for 6 years. They were divided into five lots: Control, no fluoride supplement (I); continuous exposure to 1.5mg F/kg body weight per day (II and IV); alternating exposure to 1.5mg F/kg for 6 months and control for 6 months (III); or 3.0mg F/kg for 4 months and .75mg FAg for 8 months (V). The average yearly exposure of Lot V was equal to Lots II and IV while that of Lot III was equal to half of this intake.None of the fluoride treatments affected growth rate or reproduction. There was no consistent effect on milk production. Plasma fluoride concentrations closely followed current fluoride intake. Urinary fluoride concentrations varied with intake but remained elevated during low intake. Skeletal fluoride retention was directly related to total fluoride intake and not to pattern of intake. The degree of dental fluorosis was related to the amount of fluoride fed and to the plasma fluoride concentration at the time each incisor was developing. The dental lesions observed in Lot III (alternate exposure) were similar to those often seen in field cases of fluoride exposure.The most severe effects of fluoride ingestion were in Lot V (high and low intake). These animals had severely worn molar teeth, extensive osteofluorosis, and they experienced periods of extreme lameness. Short periods of high fluoride intake balanced by periods of lower intake were more damaging to cattle than constant exposure to the same average yearly intake.