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Water Quality Ambient Water Quality Criteria for Fluoride 6.0 Livestock Effects The effects of fluoride in drinking water on animals are analogous to the effects on man (McKee and Wolf, 1963). Fluoride accumulates in bone rather than soft tissues, leading to tooth damage and bone lesions (Rose and Marier, 1977), but is transferred only slightly to eggs (Messer et al., 1972). Fluoride is transmitted to the fetus through the placenta (Anon, 1974). The addition of fluorides to a cow's food or water has little effect on fluoride levels in the milk (Anon, 1973; McClure, 1949; Tobey, 1937; and Greenwood et al., 1964). Fluoride at 500 mg/L in the water resulted in increases in the milk of less than 0.5 mg/L (Smith et al., 1945), while fluoride at 109 mg/kg in the feed for seven years only brought milk levels up to 0.2 mg/L (Greenwood et al., 1964). Concentrations of 30 to 50 mg/kg fluoride in the feed are considered safe for dairy cows (Anon, 1971b); however, retarded weight gain in sheep resulted from 25 months of 53 to 70 mg/kg fluoride in their diet (Said et al., 1972) and daily weight gain in young pigs was decreased by about 4%/100 mg/kg of fluoride in the feed over the 18-week growing period (Rose and Marier, 1977). Although beneficial in improving resistance to decay in teeth, fluoride has not been unequivocally demonstrated to be an essential element (Anon, 1971a). Water with 1 mg/L fluoride is beneficial, but at 30 mg/L fluoride the water is toxic to most livestock, and 1 mg/kg fluoride in feed is adequate to prevent deficiency symptoms. Mineral supplements may be a source of excessive fluoride since some rock phosphates and bone meals are very high in fluoride. Livestock drinking water should not exceed 2 mg/L (Anon, 1973; Anon, 1980; and Anon, 1984), since excess fluoride affects breeding efficiency and mottles teeth (Anon, 1973). Cattle develop mottled teeth when given water with fluoride at 0.5 to 0.6 mg/L, and teeth are eroded at 3.3 mg/L (Hibbs and Thilsted, 1983), or 4 to 5 mg/L (Obel, 1971). Other references indicate that tooth mottling does not occur until 1 to 2 mg/L fluoride, and that several times more is required for other tissue damage (Anon, 1973; McKee and Wolf, 1963; Anon, 1971b; Schroeder et al., 1968; Saville, 1967; Shupe et al., 1964; Anon, 1966; and Harris et al., 1963). Signs of fluorosis in livestock include mottling, chalkiness, staining, hyplasia, abrasion and excessive wear of permanent teeth in animals over two years old. Skeletal deformation, lameness, stiffness and treading of the feet occur, as well as anemia, hypothyroidism, stunted growth, delayed estrus, poor breeding and general adverse health effects (Tillie, 1970). Table 6.3 summarizes typical tissue levels related to diet.
The major source of fluoride is browse contaminated by aerial deposition in industrial areas (Anon, 1971a), though there are some areas with naturally high levels in the soil. Hay from areas presumed free of industrial fluoride pollution in the United States ranged from 0.8 to 36.5 mg fluoride/kg of hay with a mean of 3.6 and median of 2.0 mg/kg (Suttie, 1969). The levels of fluoride in forage in British Columbia are not known since forage has not been systematically analyzed for fluorides. Cereals usually contain 1 to 3 mg fluoride/kg of grain (Anon, 1980). Forage in most unpolluted areas contains 2 to 16 mg fluoride/kg forage (dry weight), but crops grown in high fluoride soils in non-industrial areas of Tennessee had fluoride levels in the 25 to 300 mg fluoride/kg crop range (Suttie et al., 1972; and Merriman and Hobbs, 1962). In areas known to be affected by atmospheric pollution, fluoride levels may range from 7 to 292 mg fluoride/kg forage on a dry weight basis and vary seasonally (Anon, 1971a). Mixed forages can contain 15 to 25 mg fluoride/kg forage when the irrigation water contains 6.2 mg fluoride/L (Rand and Schmidt, 1952). Fluoride levels in forage are primarily due to deposition of particulate fluoride on the surface of the plants; little is actually incorporated into the plant. Dairy feed and mineral supplements may contain high levels of fluoride, up to 200 mg/kg, though most are under 30 mg/kg. Cows may thus get more than their recommended daily dose of fluoride from this source before water and forage are even considered (Suttie, 1969). Bone meal supplements can be very high in fluoride since cattle grazing contaminated pastures may accumulate 10 g fluoride/kg of bone; the normal level is around 1.5 g fluoride/kg (Anon, 1980). It is recommended that such products not be marketed if their fluoride levels exceed 5 to 10 mg fluoride/kg of product. Levels in excess of this put severe restrictions on the levels of fluoride which can be accepted in forage and water, if the acceptable total fluoride dose in the diet is not to be exceeded.
The toxic effects of fluoride can be affected in several ways. Alternating high and low fluoride levels have been shown to be more toxic than a steady dose of the same total amount over a period of time (Suttie et al., 1972). Fluoride toxicosis is reduced if the diet is high in calcium (Lawrenz and Mitchell, 1941; Ranganathan, 1941; Peters, 1948; Danowski, 1948; Weddle and Muhler, 1954; Boddie, 1957; Boddie, 1960; and Suttie et al., 1957), sodium chloride (Ericsson, 1968), aluminum oxide (Boddie, 1960), calcium carbonate (Boddie, 1960; and Suttie et al., 1957), aluminum sulphate (Greenwood et al., 1964; Hobbs et al., 1954; Hobbs and Merriman, 1962; and Allcroft et al., 1965), aluminum chloride (Hobbs et al., 1954; and Sharpless, 1936), or aluminum acetate, (Hobbs et al., 1954; and Sharpless, 1936). Aluminum salts must be fed simultaneously; they will not deplete already deposited fluoride. Aluminum compounds may, however, affect dietary phosphorus retention and, if used to alleviate fluoride toxicosis, supplemental phosphorus may have to be fed as well (Hobbs et al., 1954; Street, 1942; and Alsmeyer et al., 1963).
Criteria from the literature are summarized in Table 6.1. The surface water quality objective for fluoride in Alberta and Saskatchewan is 1.5 mg/L (Anon, 1975; Anon, 1977; and Anon, undated). In Manitoba it is 1.0 mg/L for all types of use and areas (Anon, 1979). Class 4B waters in Manitoba, used for agriculture and wildlife, should not exceed 2.0 mg/L (Anon, 1980). In Ontario, water used for livestock watering should not exceed 2.0 mg/L (Anon, 1984). Table 6.2 gives some safe total dietary levels of fluoride for livestock. However, this total includes feed, forage, mineral supplements and drinking water. Generally, since their exposure times are much shorter, finishing or slaughter animals can be exposed to higher levels of fluoride than breeding stock, laying hens or dairy cows.
The total fluoride recommendation for dairy cows, breeding stock and other long-lived animals is a 30-day average of 1.0 mg/L. The maximum level is 1.5 mg/L. The recommended fluoride level in the drinking water of all other livestock is a 30 day average of 2.0 mg/L and a maximum of 4.0 mg/L, unless fluoride is present in feed or mineral additives in which case a 30 day average of 1.0 mg/L and a maximum of 2.0 mg/L is recommended (Anon, 1980; Marier, 1977; Hart, 1974; Anon, 1984; Williamson, 1983; Anon, 1979; and Anon, 1980). The CCME guidelines are 1.0 mg/L when fluoride supplements are fed, and 2.0 mg/L otherwise (Anon, 1987).
Effects on livestock, wildlife and people are basically the same and occur at about the same fluoride levels. Aesthetics of mottled teeth are considered when people are concerned, but only function is considered when livestock and wildlife are concerned. Thus slightly higher levels of fluoride can be tolerated by livestock and wildlife. Dairy cattle appear to be the most sensitive livestock to fluoride toxicity. They have high food and water uptake rates and long productive lives which leads to maximal opportunity for fluoride to accumulate to harmful levels in the bones and teeth. Birds, sheep, swine and horses are less sensitive to fluoride. Apart from breeding stock, most other livestock is slaughtered well before fluoride accumulation would become a problem. For dairy cattle, the recommended maximum dietary fluoride levels are 30 mg fluoride/kg feed (Puls, 1981), or 30 to 50 mg fluoride/kg dry matter consumed (Fisher and Waldern, 1979). A food consumption rate of 30 g dry matter/kg of animal, for a 600 kg dairy cow, results in a fluoride uptake rate of 0.9 mg fluoride/kg of cow (Bowden et al., 1981; and Richy et al., 1961).
30 g feed/kg cow x 0.030 mg fluoride/g feed = 0.9 mg fluoride/kg cow Existing evidence indicates that the average dose of 1 mg fluoride per kg body weight per day by livestock during their productive lives has no demonstrable injurious effect (Gisiger, 1968; Neeley and Harbough, 1954; and Schmidt et al., 1954). This total fluoride load needs to be partitioned between feed and water. While the fluoride level may exceed 30 mg fluoride/kg feed in some polluted areas or areas of natural high fluoride soils (Suttie et al., 1972; Anon, 1971a; Merriman and Hobbs, 1962; and Rand and Schmidt, 1952), typical levels are 1 to 3 mg fluoride in cereals (Anon, 1980), 2 to 16 mg fluoride in forage (Suttie et al., 1972), and 0.8 to 36.5 mg fluoride (mean of 3.6) in hay (Suttie, 1969). If we assume a high fluoride level in the feed of 15 mg fluoride/kg feed then the feed contributes 0.45 mg fluoride/kg animal leaving 0.55 mg fluoride/kg animal for water and mineral supplements. 30 g feed/kg cow x 0.015 mg fluoride/g feed = 0.45 gm fluoride/kg cow A 600 kg dairy cow may drink 200 mL of water per kg of its weight. If the water contains 2 mg fluoride/L then the uptake of fluoride from the water is 0.4 mg fluoride/kg of cow. 0.2 L/kg cow x 2.0 mg fluoride/L = 0.4 mg fluoride/kg cow This gives a total of 0.45 mg fluoride from the feed plus 0.4 mg fluoride from the water, for a total of 0.85 mg fluoride/kg of cow from food and water leaving 0.15 mg fluoride/kg of cow for mineral supplements and prepared feeds.
1.0 mg fluoride/kg (total)-0.45 mg fluoride/kg (feed)-0.40 mg/kg (water) = 0.15 mg fluoride/kg cow While such supplements may have very high fluoride levels most are under 30 mg/kg of supplement (Suttie, 1969). At the level of 30 mg fluoride/kg supplement up to 17% of the cows total daily diet could come from supplements and the maximum dietary fluoride level would not be exceeded. 0.15 mg fluoride/kg cow/(0.030 mg fluoride/g suppl x 30 g feed/kg cow) = 17% of diet If water supplies contained only 1 mg fluoride/L then supplements could reach 40% of the daily ration without exceeding the daily fluoride dose. (0.15 + 0.20 mg fluoride/kg cow)/(0.030 mg fluoride/g suppl x 30 g feed/kg cow) = 40% of diet Low fluoride supplements should be selected for feeding cattle since some of the highest ones on the market would supply the entire daily dietary fluoride ration if fed at 17% of the total diet, leaving no room for contributions from feed and water (Suttie, 1969).
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