Copper poisoning threatens food chain

Excessive supplementation can lead to copper poisoning of stock, as the element accumulates in animals' livers. "It's excessive supplementation that raises its head time and time again," said Dr Jo Payne from the Veterinary Laboratories Agency (VLA).

Copper can cause premature cattle death and threaten human health if not identified in cattle, as it can be carcinogenic. Presenting to the Advisory Committee on Animal Foodstuffs (ACAF) last month, Payne said: "Concern has been expressed by the Food Standards Agency that, following relaxation of OTMS (Over Thirty Month Slaughter Scheme) Regulations, cull cows can enter the food chain, and their livers [can be] used in food products."

Copper levels in cows' livers had been "creeping up over the last few years" and it could taint liver pâtés, as dairy cattle entered the food chain, she said.

Peter Bone of supplement specialist Telsol, co-presenter with Payne, fears over-supplementation is more widespread in the UK than was commonly recognised. "We feel the VLA is only seeing the tip of an iceberg."

Bar a vet's prescription, the top legal level of elemental copper is 40mg/kg of total diet dry matter (DM). The VLA wants a normal formulation level of 18mg/kg DM.

Insufficient controls in the way farmers added copper often led to over-supplementation, Payne said. Many British forages were low in copper, raising the copper deficiency risk in unsupplemented diets, she added.

546 cases of copper deficiency had been diagnosed in suckler beef cattle since 2005, she said.