The effect of dietary molybdenum and iron on copper status and growth in cattle

Abstract

SummaryThe effects of supplementation of a barley-barley straw diet containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 mg iron (Fe)/kg D.M. on the Cu status, growth and clinical condition of calves are described. Liver and plasma Cu concentrations declined rapidly within 12–16 weeks to levels indicating severe Cu deficiency in both the Mo- and Fe-supplemented groups. The changes in Cu status were similar for both supplements and did not differ significantly from each other. Clinical signs of Cu deficiency, as indicated by reduced growth rate and changes in hair texture and colour, were evident after 16–20 weeks only in animals on the Mosupplemented diet. The reduced growth rate was accompanied by a decreased food intake and reduced efficiency of food utilization. The Mo-supplemented animals also exhibited an altered Fe metabolism, particularly when the growth rate was affected. The results confirm earlier reports that the effects of Mo on growth and clinical condition are independent of its effect on Cu status and suggest that the altered production might be due to effects on the control of food intake, food utilization, or Fe metabolism.