The availability of copper to grazing ruminants in parts of North Yorkshire

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Abstract
Summary: A total of 225 herbage samples were taken from two areas with a history of bovine hypocupraemia and examined for their Cu, Mo, total S, Zn, Fe and Cd content.In general, the concentrations of Cu and Mo (mean values 10·4 and 1·6 mg/kgD.M. respectively) were normal, as were those of Zn, Fe and Cd (mean values 43, 255 and 0–59 mg/kg D.M. respectively). The total S concentrations (mean value 3·5 g/kg D.M.) were, however, higher than found by some other workers.The concentrations of available herbage Cu were calculated using the following relationship of Suttle & McLauchlan (1976):logTA Cu = –0·0019 Mo–0·0755 S–0·0131 Mo × S–1·153,where TA Cu is the true availability of Cu, and Mo and total sulphur (S) are dietary concentrations as mg/kg D.M. and g/kg D.M. respectively. Animal requirements for available Cu were derived from estimates of the factorial Cu requirements of various classes of livestock, and when these were compared with the calculated concentrations of available Cu in the herbage they provided a possible explanation for the widespread hypocupraemia experienced in these areas.
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