Proteins involved in iron metabolism in beef cattle are affected by copper deficiency in combination with high dietary manganese, but not by copper deficiency alone.

A 493-d study was conducted to determine the impact 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 high Mn (-Cu+Mn). Copper deficiency was induced through the addition of 2 mg of Mo/kg of DM. After weaning, calves remained on the same treatment as their dam through growing (basal diet analyzed 7 mg of Cu/kg of DM) and finishing (analyzed 4 mg of Cu/kg of DM) phases. Plasma Fe concentrations were positively correlated (P < 0.01; r = 0.49) with plasma Cu concentrations. Liver Fe concentrations were greater (P = 0.05) in -Cu vs. +Cu calves and further increased (P = 0.07) in -Cu+Mn vs. -Cu calves. There was a negative relationship (P < 0.01; r = -0.31) between liver Cu and Fe concentrations. This relationship is likely explained by less (P < 0.01) plasma ceruloplasmin activity in -Cu than +Cu calves. As determined by real-time reverse transcription-PCR, relative expression of hepatic hepcidin was significantly downregulated (>1.5 fold) in -Cu compared with +Cu calves (P = 0.03), and expression of hepatic ferroportin tended (P = 0.09) to be downregulated in -Cu vs. +Cu. In the duodenum, ferritin tended to be upregulated in -Cu. vs. +Cu calves (P < 0.06). No significant change (P > 0.2) due to Cu-deficiency was detected at the transcriptional level for either isoform of divalent metal transporter 1 (DMT1 mRNA with or without an iron responsive element; dmt1IRE and dmt1-nonIRE) in liver or intestine. Duodenal expression of hephaestin and ferroportin protein was not affected by dietary treatment (P > 0.20). However, duodenal expression of DMT1 protein was less (P = 0.04) in -Cu+Mn steers vs. -Cu steers. In summary, Cu deficiency alone did affect hepatic gene expression of hepcidin and ferroportin, but did not affect duodenal expression of proteins important in Fe metabolism. However, the addition of 500 mg of Mn/kg of DM to a diet low in Cu reduced duodenal expression of the Fe import protein DMT1.