No abstract

Groups of lactating cows were fed 0, 40, and 200 mg of added cadmium (as chloride) and 0, 100, and 500 mg of added lead (as acetate) per animal per day in separate experiments. Milk and blood were sampled periodically and analyzed for concentrations of metal ions. Metal feeding was discontinued after 3 mo, and selected animals were necropsied for tissue residue studies. Remaining animals were continued on control ration for another 3 mo and then killed and tissues obtained. Cadmium feeding did not produce a dose-related increase of this metal in blood, milk, or skeletal muscle. Liver and kidneys were the primary organs of cadmium accumulation, and concentration of cadmium in these organs continued to rise during 3 mo of feeding the control diet after the initial exposure period. Lead did not accumulate in skeletal muscle but showed a dose-related increase in blood, milk, bone, liver, and kidney. In most tissues there was a rapid decline of lead concentrations after cessation of treatment, except in bone. Low dietary intake of cadmium and lead do not produce an appreciable rise of these metals in edible products, e.g., milk or meat. Of the tissues analyzed, liver and kidney accumulate both cadmium and lead, and cadmium especially persists in these organs for long periods. Bone is the primary site of deposition for lead but not cadmium.

Cattle normally ingest variable low-level amounts of fluorides with no known adverse effects, but when excessive amounts are ingested, adverse effects are induced. Several sources may contribute to the total fluoride intake. The many recognized factors that influence structural and functional responses of animals to fluorides are cited. Signs and lesions of fluoride toxicosis in cattle have been characterized. Major fluorotic lesions occur in the permanent teeth and in the bones. Dental lesions occur when excessive amounts of fluoride are ingested during the period of tooth formation and calcification. Bone effects can be induced at any time during an animal's life. A table relating structural changes and functional processes in cattle of various ages has been compiled as a guide for diagnosing and evaluating fluoride toxicosis. Recommended fluoride tolerance levels for cattle have been established. Prevention and control of fluoride toxicosis in cattle can be accomplished when the nature of the disease is realized; the symptomatology, lesions and pathogenesis are properly interpreted, correlated and evaluated; and the source(s) of excessive fluorides are eliminated.

IntroductionFluorine occurs throughout the world in soils, plants, water, and animal tissues.Because of its chemical reactivity, it is found in nature in a combined form.Cattle normally ingest variable amounts of fluorides ( u p to 15 ppm F in dry matter) throughout their lives with no known adverse effects. If amounts above the borderline critical level (which varies with the animal species and the type of fluoride) are ingested over long periods of time, fluorine toxicosis may result. Because fluorine is cumulative in the animal body as long as the animal continues to ingest a constant or increasing amount, the major fluorine problem in livestock has involved chronic toxicosis. This has become an important toxicologic problem in some areas in this and other countries.Various sources may contribute to the total fluorine intake by animals. The most commonly encountered sources of excessive fluoride are: ( 1 ) forages subjected to air-borne contamination in areas near certain industrial operations that heat fluorine-containing materials to high temperatures and expel fluorides; (2) drinking water high in fluoride content; ( 3 ) feed supplements and mineral mixtures high in fluoride content; and (4) vegetation growing on soils high in fluoride content.It is generally accepted that the toxicity of a fluoride compound increases as its aqueous solubility increases. Recent experiments with dairy cattle that were fed controlled amounts of different fluorides have indicated that calcium fluoride is less toxic than sodium fluoride or than hay containing fluoride emitted from a n industrial plant (FIGURE 1).Elevated vegetation levels of fluorine generally result from increased atmospheric fluorides. In at least some cases, a large fraction of these fluorides seems to be deposited on the surface of the leaves and, thus, can be readily removed by rain or washing. Particulate fluorides are more likely to accumulate on plant surfaces than gaseous fluorides. Surface contamination of plants by fluoride in dust o r mud splashed on leaves near the ground may also occur and contribute