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(Iron Storage Disease)

This is a disease that is still being researched, and there are many questions still unanswered. I do not believe that with a normal diet this is a problem with European Starlings; however, the message board receives numerous questions about it, so I thought this page would be of benefit. Wild European Starlings normally have an iron content in their organs 2-10 times higher than in chickens or quails, especially in the liver (1310-3300 pg Fe/g wet) and feathers (380_78O~g/g wet). The iron concentration per body weight ranged from I53 to I85 ppm, which was 24 times higher than the values for other birds or mammals. (Garcia, Planas 1984) I believe this normal high iron concentration is one of the reasons that European Starlings are often said to be susceptible to hemochromatosis.

Iron is a necessary component of the diet and is found in every cell in the body. It is involved in a wide range of processes including cell respiration, DNA synthesis, and is a part of many enzymes. It serves as a cofactor to the enzymes needed for the electron transport chain, from which ATP is generated. Iron in the body is predominantly found bound to the proteins hemoglovin and myoglovin, which serve to carry and release oxygen." (Crissey, Trusk 1993).

"In captive starlings the absorption of 59Fe was measured by whole-body counter after varying degrees of liver iron loading (by i.m. injections of iron dextran). The haemosiderosis, which occurred particularly in the post-moult period, had no detrimentral effect on liver functions. Birds with haemosiderosis absorbed up to 10% of an orally administered test dose of the radioactive iron, even when the hepatic iron concentrations were markedly increased. It was concluded that the absorption of iron at the intestinal mucosa in avian species is not as tightly regulated as that in some mammals." ( Ward, Smith, Henderson, Peters 1991).

Any animal or human can get the disease. In birds it is a disease of primarily fruit eating birds, (frugivorus) such as Mynahs, Toucans, and Lories. In a laboratory you can induce it by massively overdosing an animal with iron, as the body can not expel the overload of induced iron quickly enough. This is true of anything, for you can also cause toxicity with massive overloads of water as well. In a healthy animal the body excretes the excess iron, but for some reason with Hemochromatosis the body no longer excretes the iron but starts to store it in the liver. It can cause the accumulation of fluids in the body with difficulty breathing, and it can involve the heart and other organs. If accumulated in large concentrations, iron is toxic to liver cells. Toxicity can lead to cell death and fibrosis.

Iron storage is not usually caused by dietary iron, but some years ago the theory was that perhaps the iron in the diets of some captive birds was causing the overload of iron, and some genetic factor was the reason for it. Hemochromatosis is not known to be in wild populations of birds; it is considered to be a disease of captive birds, yet in the wild, a mynah's main diet is figs, which have a very high iron content; if this were a genetic problem, then you would expect to see it in wild populations.

Dietary components that increase the storage of iron include Vitamin C, ascorbic acid (citrus fruit) and sugar. Other things such as copper and tannin compete with, or bind up iron so that it isn't as available. The figs I mentioned are also very high in tannin. I believe that it will be shown that the tannin in the native fruit and water of susceptible birds is one of the main reasons it isn't seen in the wild. In an article on tannin found in Green Tea the "Alternative Medicine Review" - Volume 5, Number 4, August 2000 states that "green tea polyphenols stimulate the activity of hepatic detoxification enzymes, thereby promoting detoxification of xenobiotic compounds, and are also capable of chelating metal ions, such as iron, that can generate radical oxygen species." To read the full article go to Green Tea. Additionally, Zhi Zhong, PhD, from the University of North Carolina at Chapel Hill, and colleagues looked at whether the powerful, free-radical scavenging antioxidants in green tea could alleviate some of the problems associated with fatty livers. They found that "Green tea extract scavenges harmful free radicals in fatty livers and therefore could be an effective treatment to prevent failure of liver transplants."

In a study at Brookfield Zoo, fifty eight European Starlings were studied after feeding one group a low iron diet of 148 ppm and the other group a high iron diet of 3,035 ppm of iron. All birds were euthanized after four months and tested for iron storage. Birds in both groups had similar liver iron content, but the birds on the high iron diet had significantly higher values. Yet with this massive overdosing of iron, none of the birds had developed Hemochromatosis.

Riverbanks Zoo did a similar study with fifty European Starlings. They were fed a normal dog food diet for six months to one year; half of them were also given tannin in their water. They were tested for iron storage, and no difference was found between the two groups. The iron was increased to 800 ppm and the birds were tested again; the birds given the tannin had lower amounts of iron in the liver than the birds without tannin. Again, 800 ppm is an excessive amount of iron and not representative of a normal diet. No European Starling in these studies developed Hemocromatosis.

Thomas Roudybush writes: "Recent biochemical evidence indicates that immunologic stress raises the level of iron-binding proteins that function in iron transport and that synthesis of these proteins is regulated by stress hormones. With our present level of understanding of iron-storage disease, it appears that nutrition is, at best, a minor player in the disease. Stress factors, as mediators of iron metabolism, need further investigation". (Roudybush,1999)

No one knew up until recently what exactly regulated the control of iron in the body. A few years ago hepicin was discovered. It is believed to be the protein regulator of iron accumulation.

Hepicin is located in the liver, and when its levels are high it blocks the delivery of iron to the cells and blood, and the excess iron is excreted. Not only does hepcidin appear as a key regulator of body iron content, but it may play an important role in defense against infection by depriving microorganisms of a ready source of iron.

I believe that the ability of tannin to chelate iron has caused us to overlook the fact that tannin also protects the liver because of its Anti-Oxidation and Anti-Microbacterial activity. Theoretically, in birds, tannin could increase or protect the naturally occurring hepcidin in the body, as several studies have reported an increase in protein flow when moderate doses of tannins were used. Current research has shown that after administration of lipopolysaccharide (LPS), an iron chelator, that hepicin increased, thereby blocking the iron not only in the liver but also in the intestines. Even though this hasn't yet been researched in birds, I believe that the iron chelator tannin could very well have this same effect.

NOTE: Tannin's effect on iron storage was recently researched at Texas A & M University and it was found that the addition of inositol or tannic acid may be a reasonable alternative to low iron diets. It was also found that tea didn't reduce the iron levals in the liver of birds with already high levals of iron, but that tannin helped in preventing the absorption of iron. (D.Phalen)

We know that in the wild toucans and mynahs receive tannin in their diet and drinking water, and this is the substance that is most lacking in the captive diet. We also know that hemochromatosis is not a disease of wild birds. In one antidotal experiment mynahs were given free choice a bowl of tannin water and a bowl of plain water each day; the mynahs seemed to self regulate the amount of tannin water they consumed. Research has shown that starlings can not only taste tannin but can also judge its strength. (Espaillt, Mason 1990)

As there are many links to hepcidin on Google I won't list any here.

The ppm of iron found in different dog food types and brands:
Purina - adult dry dog chow 269, puppy 287
Purina Moist N Meaty - chicken 365, beef 471
Science Diet dry - adult 184, puppy 338
Poultry mash (approx.) 240 ppm

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My thanks to Martin Vince for his kindness in sharing information on the Riverbanks project.

Literature Cited:
D Phalen, Falcon, Dierenfield, Russell, Olsen, From a yet unpublished, but accepted for publication, research paper "Impact of Supplements on Iron Absorption from Diets Containing High and Low Iron Concentrations in the European Starling (Sturnus vulgaris)"

J.E. Espaillat and J R Mason,1990, Differences in taste preference between Red-Winged Blackbirds and European Starlings. Wilson Bull,102 (2) pp 292-299

F. Garcia, J. Ramis and J. Planas, 1984, Biochem. Physiol. Vol. VA, No. 4, pp. 651-654,

Ward, R. J. Smith, T. Henderson, G. M. Peters, T. J., 1991, Avian Pathology, Vol. 20, No. 2, pp. 225-232

S.D. Crissey, A. M. Trush, S Black, P. McGill 1993, Effect of dietary iron on the accumulation of iron in the liver of European Starlings. Proceedings American Association of Zoo Veterinarians

Thomas E. Roudybush, 1999, Psittacine Nutrition. Veterinary Clinics of North America: Exotic Animal Practice Vol. 2 Number 1.

Park, C.H., Valore, E.V., Waring, A.J., & Ganz, T. (2001). Hepcidin: a urinary antimicrobial peptide synthesized in the liver. J. Biol. Chem. 276, 78067810

Copyright © 1999-2011 Jackie Collins - All rights reserved.