Heavy metal contents of livestock feeds and animal manures in England and Wales

Abstract In this study, 183 livestock feeds and 85 animal manure samples were collected from commercial farms in England and Wales and analysed to determine their heavy metal (zinc, copper, nickel, lead, cadmium, arsenic, chromium and mercury) contents. Zinc and copper concentrations ranged from 150–2920 mg Zn/kg dm (dry matter) and 18–217 mg Cu/kg dm in pig feeds, depending on the age of the pigs. In poultry feeds, concentrations ranged from 28–4030 mg Zn/kg dm and 5–234 mg Cu/kg dm, with laying hen feeds generally having higher heavy metal contents than broiler feeds. Concentrations of Zn and Cu in dairy and beef cattle feeds were much lower than in pig and poultry feeds. Pig manures typically contained c.500 mg Zn/kg dm and c.360 mg Cu/kg dm, reflecting metal concentrations in the feeds. Typical concentrations in poultry manures were c.400 mg Zn/kg dm and c.80 mg Cu/kg dm, and in cattle manures c.180 mg Zn/kg dm and c.50 mg Cu/kg dm. The dry matter content of cattle and pig slurries was a useful indicator of heavy metal concentrations on a fresh weight basis.