The importance of molybdenum, sulphur, iron, zinc and cadmium dietary antagonists to ruminant copper metabolism was investigated at the farm level in an attempt to explain the widespread occurrence of bovine hypocupraemia in recent years.
From 22 of the most severely hypocupraemic regions of England, six areas with as wide a range of geological, pedological and topological situations as possible were selected for detailed field work. This involved the collection of topsoil and herbage samples from approximately 15 farms per area with hypocupraemic stock. Possible causal factors of bovine hypocupraemia were then considered on the basis of three criteria: critical concentrations of copper, molybdenum, sulphur, iron, zinc and cadmium in pasture herbage; Cu:Mo ratios in herbage; and copper availability predictions for ruminants.
Absolute copper deficiency and molybdenum-induced bovine hypocupraemia were clearly demonstrated at the farm level. The results also confirmed that dietary sulphur, in particular, plays a significant yet previously unrecognized role in the widespread incidence of bovine hypocupraemia in industrialized Britain. Antagonism due to iron orginating from soil-contaminated herbage was evident, but not common. No evidence was found to support the occurrence of zinc- or cadmium-induced hypocupraemia in the areas examined.