Nutritional Interrelationships between Iron, Copper and Manganese in Domestic Livestock

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Title: Nutritional Interrelationships between Iron, Copper and Manganese in Domestic Livestock
Author: Hansen, Stephanie Laura
Advisors: William Flowers, Committee Member
Vivek Fellner, Committee Member
Jerry Spears, Committee Chair
Jack Odle, Committee Member
Abstract: Oftentimes the diets of cattle and pigs contain levels of iron well beyond the nutritional requirement of the animal. This superfluous iron may come from feedstuffs naturally high in iron, or from the consumption of soil, though bioavailability of iron from soil is unknown. Additionally, excess iron in cattle diets has been shown to negatively impact the metabolism of manganese and copper, though the molecular mechanism behind this interaction is unclear. The purpose of this research was threefold: 1) to determine the effect of ensiling on bioaccessibility of iron from soil contamination of corn greenchop, 2) to identify proteins important in iron metabolism in bovine and swine, and 3) to determine if these proteins are affected by dietary iron concentration. The results reported herein suggest that bioaccessibility of iron from soil contamination is greatly increased when soil undergoes a prolonged exposure to a low pH environment, such as that found with fermenting forages. These data indicate that very little iron from soil is available to the animal if no prior exposure to an acidic environment occurs. Also, for the first time we report that several proteins known to be essential to iron metabolism in rodents are present in bovine small intestine and liver. Specifically, the iron importer divalent metal transporter 1, the iron exporter ferroportin, and the multi-copper ferroxidase hephaestin were all present in bovine duodenum. In the bovine, reduced iron status, as induced by a primary deficiency of copper, resulted in increased gene expression of divalent metal transporter 1 and ferroportin in duodenum and decreased expression of the ferroportin regulatory hormone hepcidin and divalent metal transporter 1 in liver. Protein expression of ferroportin and hephaestin were also increased in duodenum due to reduced iron status. The addition of excessive amounts of iron to the diets of young calves also appeared to regulate protein expression of transporters important in iron metabolism. Specifically, high iron tended to decreased duodenal protein levels of divalent metal transporter 1 and reduced ferroportin protein levels, though no effect on hephaestin was observed. We also examined iron metabolism in the young pig, in order to examine the effect of an iron deficient diet on expression of these proteins. We found that hephaestin protein in the duodenum was lowered by feeding a high iron diet, and levels of both ferroportin and divalent metal transporter 1 tended to be reduced by high dietary iron compared to pigs fed a low iron diet. Additionally, we found that feeding a high iron diet to pigs negatively impacted liver concentrations of manganese. And feeding a high iron diet to either pigs or calves reduced duodenal concentrations of manganese, suggesting that high dietary iron reduces manganese absorption. Because high iron diets fed to both pigs and calves tended to reduce duodenal levels of divalent metal transporter 1, a protein known in rodents to transport both iron and manganese, it appears that the observed reductions in duodenal manganese concentrations may be a result of reduced transporter availability. Collectively, our data suggest that high dietary iron may negatively affect manganese absorption, and because the iron content of livestock diets is often high, further research is warranted.
Date: 2009-03-04
Degree: PhD
Discipline: Nutrition

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