Iron-induced copper deficiency in calves: dose-response relationships and interactions with molybdenum and sulphur

Abstract

ABSTRACTThe effects of dietary supplements of iron, molybdenum and sulphur on copper metabolism in calves were examined. In one experiment, 27 castrated male pre-ruminant Friesian calves were given a milk-substitute ration containing 0·9, 4·5 or 9 mmol iron per kg dry matter for 8 weeks. The iron supplements had no effect on liver copper retention. When 24 of these calves were then given a diet based on barley grains and barley straw containing 0, 4·5, 9 or 13·5 mmols iron per kg for up to 24 weeks, liver and plasma copper concentrations were greatly reduced in all iron-supplemented animals but no clinical signs of copper deficiency developed. Reduction in the dietary sulphur concentration from 88 o t 47 mmol/kg after 12 weeks did not prevent the iron-induced reduction in liver copper concentrations n i animals given 9 or 13·5 mmol iron per kg. Plasma copper concentrations increased in all iron-treated calves given the low-sulphur diets, except in animals given 13·5 mmol iron per kg. The results indicate that iron is a potent antagonist of copper metabolism in weaned calves and that its effects are probably independent of dietary sulphur supply.In a second experiment 20 Hereford × Friesian female calves were given diets with supplements of 2·7 mmol iron and 20 μmol molybdenum per kg, separately and together, for 41 weeks. Both supplements reduced liver and plasma copper concentrations but only in the molybdenum-treated animals were live-weight gains reduced. The rate of decline in liver and plasma copper concentrations tended to be greatest in animals given both supplements, indicating that additive action of these antagonists is possible.