An effect of soil ingestion on the utilization of dietary copper by sheep

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Abstract
To test the hypothesis that the ingestion of Mo-rich soils by ruminants might adversely affect Cu metabolism, four groups of initially hypocupraemic ewes were repleted with a Cu-supplemented diet either soil-free or containing 10% of one of three soils of low, medium and high Mo content. The three soils were equally effective in inhibiting the response in plasma Cu and probably reduced the availability of Cu by more than 50%. The ingestion of certain soils produced increases in urinary Mo and Zn concentrations, indicating that the Mo and Zn ingested in soil can be biologically available: however, these Cu antagonists were probably released in insufficient quantities to have contributed greatly to the observed interference with Cu metabolism. Soil ingestion may be involved in the aetiology of hypocuprosis in cattle and swayback in sheep, since it commonly constitutes 10% of the D.M. intake of animals grazing winter pasture.
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