Ruminant Nutrition: Minerals and Vitamins

Iron (Fe) and copper (Cu) metabolism are closely intertwined, and a deficiency of Cu may lead to a secondary Fe deficiency. The impact of a severe Cu deficiency on proteins involved in Fe metabolism in the bovine has not been studied. Therefore, a 493 day study was conducted to determine the effect of a severe long-term Cu deficiency on Fe metabolism in beef cattle. Twenty-one Angus calves were born to cows receiving one of the following treatments: 1) adequate Cu (+Cu), 2) Cu deficient (-Cu), and 3) Cu deficient plus 500 mg Mn/kg DM (-Cu+Mn). Following weaning, calves remained on the same treatment as their dam through growing (basal diet analyzed 7 mg Cu/kg) and finishing (analyzed 3 mg Cu/kg) phases. Plasma Fe concentrations were positively correlated (P < 0.01; R2 = 0.49) with plasma Cu concentrations. Reciprocally, there was a negative relationship (P < 0.01; R2 = -0.31) between liver Cu and Fe concentrations. This relationship is likely explained by lower (P < 0.01) ceruloplasmin activity in -Cu. vs. +Cu calves. Based on Western blotting of duodenal mucosal scrapings collected at harvest, concentrations of hephaestin (Hp), a Cu-dependent ferroxidase, were greater (P = 0.01) in -Cu+Mn compared to -Cu calves. Similarly, concentrations of the Fe export protein ferroportin (FPN) tended (P = 0.07) to be higher in -Cu+Mn vs. -Cu calves, likely due to lowered Fe status of -Cu+Mn calves. However, concentrations of divalent metal transporter 1 (DMT1), a protein responsible for import of Fe, Mn and Cu into cells, were lower (P = 0.04) in -Cu+Mn calves vs. -Cu calves. Concentrations of Hp, FPN and DMT1 did not differ (P > 0.1) between +Cu and -Cu calves. In summary, while Fe status of calves was impacted by changes in Cu status, Cu deficiency alone did not impact duodenal concentrations of proteins important in Fe metabolism. However, excessive dietary Mn appeared to regulate DMT1, and this regulation was able to override low body Fe signals.