What is the maximum amount of lead permitted in animal feed?
According to information found in NAS. 1980. Mineral tolerance of domestic animals. Natl. Acad. Press, Washington, DC. p. 256-276. Cattle, sheep, and chickens have been fed 10 ppm supplemental lead in a soluble form for extended periods without adverse effects. Significant increases in tissue lead levels occurred when 100 ppm lead was fed to the same species. Dietary lead at 1,000 ppm has been tolerated by ruminants and poultry for several months with no visible signs of toxicosis. Approximately 300 ppm dietary lead resulted in observable signs of toxicosis in horses of various ages. Young growing pigs fed 11 mg lead per kilogram of body weight suffered from diarrhea, and 33 mg resulted in decreased growth and muscle tremors. Death occurred with a dietary intake of 66 mg lead per kilogram of body weight. With regard to acute toxicosis, the ingestion of 200 to 400 mg lead (as acetate) per kilogram of body weight caused acute death in calves and lambs up to 4 months old. In older cattle and sheep, the lethal single oral dose was 600 to 800 mg/kg of body weight. A single oral dose of 500 g lead acetate (700 mg lead per kilogram of body weight) was lethal to horses. The maximum tolerable dietary level for lead is considered to be 30 ppm for most species, although detectable increases in lead concentration may occur in certain tissues.