Question: I am currently studying as a vet tech and have interesting questions that you may be able to help with.   I have a 16 yr MSF. I have many indicators of iron toxicity, the first being my demographics; I live in NH, secondly has dermatological signs of systemic imbalances including his mane and tail have been in the past very red. The reason why we removed iron from his diet was firstly a debiliating case of scratches that was remedied through removing iron from his feed. He is now getting:

Hay by weight for him is 18 -201bs daily while monitoring weight during winter. Orchard grass pasture in summer grazing muzzle always used  

4 0z. timothy pellets 

1/4 cups Omegashine ground flax

fed by label instructions:

Uckele: zinc pellets, copper pellets,  Lysine

Elevate SE/d-alpha-tocopherol acetate (natural vitamin E), selenium yeast, dextrose.

Magnesium 1/2 t

My continuing concern is in his seasonal change in performance. I am completely convinced that it is not IR or if it is it is due to damage of the liver and/or liver taxation. Additionally my reasoning is based upon his dermatological issues that are related to shedding, not foraging. Also, his lethargy is most prevalent after a summer on pasture always wearing a grazing muzzle, whereas the winter and spring he is more motivated when on hay.

Given this information I'm asking you if my plan is sound. Remember, I am a vet tech student that has limited funds and understand that typically a full blood and liver enzyme test would be the first step, however I do not have that financial luxury. Blood test in the past have not revealed to our physicians an iron toxicity/liver disease. However his scratches were (the most concerning dermatological issues)  remedied.

My plan is to treat with the only non pharmaceutical treatment I have found, a product called milk thistle. My reasoning for the herb as apposed to the liquid is education I have received has stated that he would absorb through his secum more directly to his liver than if he was to have the liquid which may be absorbed through the stomach. Do you agree?

After treatment do you suggest supplementing vitamin C to aid in future iron absorption?

Dr. Kellon:  You are certainly correct that you live in a high risk area for excessive iron intake and the coat changes, and infections you describe are common signs of iron overload and accompanying zinc and copper deficiency.

The hay made from high iron grasses is just as high, sometimes higher because of surface contamination, so other problems seen when on pasture are unlikely to be iron related.  You shouldn't guess about IR.  The test is inexpensive especially if you pull the blood and process the sample yourself, ask the practice just to bill you lab cost: 


It may be that your horse just likes cool/cold weather better (most do), but there are two other conditions that may cause fall lethargy. Lyme disease flares are very common in the fall.  There is also a natural fall rise in the hormone ACTH, which causes cortisol release and worsens IR.  This becomes larger as the horse ages.


Your supplement choices are good, but a hay analysis would be useful in telling you how much you need to supplement.  The sun really is involved in coat discoloration over the summer, but it happens because of insufficient melatin pigment, which requires copper and zinc.  You should also add an iodine source such as Ocean K to your supplements.


Normal liver indices on blood work means the liver has not been damaged enough to compromise its function.


Routine bloodwork can't diagnose iron overload. The only way to diagnose iron overload by blood work is with the iron scan at Kansas State University. You need iron, TIBC and ferritin, with ferritin being the most important test:


Note: Sample handling is very important.


There is some evidence the silimarin found in Milk Thistle can chelate iron and it is also an excellent antioxidant to protect the tissues.  However, to get a therapeutic amount from the whole herb you would have to feed around 6 to 12 ounces per day.  It would be more economical to get a standardized product in bulk, such as: a generous teaspoon once or twice a day will do it.  Also need to continue to supplement trace minerals.


Vitamin C should not be used in this situation. You will never remove even close to the total amount of iron stored in the body and the horse will be continuing to ingest a high iron diet.  Vitamin C enhances iron absorption.