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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Iron Transporters Are Differentially Regulated by Dietary Iron, and Modifications Are Associated with Changes in Manganese Metabolism in Young Pigs^1–3,

Department of Animal Science, North Carolina State University, Raleigh, NC 27695

To investigate the effects of dietary iron (Fe) on manganese (Mn) metabolism, 24 weaned pigs (21 d old) were blocked by litter and weight and randomly assigned to the following treatments: 1) no supplemental Fe [low Fe (L-Fe)]; 2) 100 mg supplemental Fe/kg [adequate Fe (A-Fe)]; and 3) 500 mg supplemental Fe/kg [high Fe (H-Fe)]. The basal diet was analyzed to contain 20 mg Fe/kg. Tissues were harvested after 32 d of feeding. Daily gain (least square means ± SEM) was greater in A-Fe pigs (328.3 ± 29.9 g/d) than in L-Fe pigs (224.0 ± 11.2 g/d). Hemoglobin concentrations on d 32 were lower in L-Fe pigs (62 ± 3.5 g/L) than in A-Fe pigs (128 ± 5.6 g/L) and did not differ between pigs fed A-Fe and H-Fe (133 ± 12.0 g/L). Liver Fe increased with increasing dietary Fe. Relative hepatic hepcidin expression was greater in pigs fed A-Fe and H-Fe than in those fed L-Fe. Relative expressions of duodenal divalent metal transporter 1 (DMT1) and solute carrier family 39 member 14 (ZIP14) were increased in L-Fe pigs compared with H-Fe pigs. Liver copper (Cu) was higher in L-Fe (0.56 ± 0.04 mmol/kg) and H-Fe (0.58 ± 0.04 mmol/kg) pigs than in A-Fe pigs (0.40 ± 0.04 mmol/kg). Liver Mn was lower in H-Fe pigs (0.15 ± 0.01 mmol/kg) than in A-Fe (0.23 ± 0.02 mmol/kg) or L-Fe pigs (0.20 ± 0.02 mmol/kg). Duodenal Mn concentrations were greater in L-Fe pigs than in A-Fe or H-Fe pigs. Fe deficiency in pigs increased gene expression of duodenal metal transporters (DMT1 and ZIP14) and supplementation with H-Fe reduced expression of DMT1 and ZIP14, which may have decreased absorption of Mn.

^* To whom correspondence should be addressed. E-mail: jerry_spears{at}ncsu.edu.

Manuscript received 17 February 2009. Initial review completed 25 March 2009. Revision accepted 21 May 2009.

Published online 17 June 2009.