Ask Horse Journal: 12/04

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Absorption And Thyroid Therapy
I have an 18-year-old Arabian gelding that has recently been diagnosed with Cushing’s syndrome. He’s been hypothyroid for about nine years. While I know that having a hay analysis done would be the first step, I wondered if any supplements might interfere with his thyroid medicine. Are there certain nutrients I should be wary of or any combination of ingredients'

Heavy concentrations of some minerals, such as calcium, in the gut at the same time as the thyroid supplement will decrease absorption. So does soy. Thyroid supplement is best given about 20 minutes before feeding the first meal of the day, either by oral syringe or in a small amount of applesauce. It can still be effective if added to a grain meal, but you must use a larger dose than if it is given separately. Large amounts of competing substances in the meal may block absorption severely. You want to make sure you have adequate levels of iodine and selenium in the diet to support thyroid hormone production and conversion to the active form.

After you begin treatment for Cushing’s, recheck thyroid levels in about 3 months. As the Cushing’s comes under control there may be less suppression of thyroid function, so that the dose of supplement may be reduced.

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Diverse Nutritional Needs
The barn I am in feeds good grass/alfalfa hay and plenty of it. My Irish Draught Horses are doing well weight wise with just hay. They’re happy out in the pasture 24/7. I anticipate that will change, however.

I have a four-year-old mare who is in foal and a yearling colt. Can I find a supplement that meets the needs of different horses without causing worry about insulin-resistance problems in these easy-keeper horses'

First, don’t assume any of your horses will need anything beyond hay. You have two basic considerations here: adequate calories and adequate protein/mineral/vitamin intake. The first is not likely to be a problem except possibly when the mare is nursing. The second is where you need to focus. Step one is to have your hay analyzed so that you know the level of minerals it’s providing and whether the balance of minerals is acceptable. Step two is to correct the mineral profile of the hay, so that all minerals are in balance by supplementing only those minerals needed.

After that, you will meet the individual needs of growing, pregnant and lactating horses by using any of the commercial supplements that are correctly balanced. You can spot these by checking the label and looking for these ratios:

• The calcium-to-phosphorus ratio should be listed as between 1.5:1 and 2:1.
• Copper:Zinc:Manganese 1:3:3 to 1:3:2.5
• Iron:Copper no more than 4:1

For horses that are insulin-resistant, we also recommend Calcium:Magnesium of 2:1.

You’re not likely to need any additional protein if there are generous amounts of alfalfa in the hay, but if the need arises for protein (pregnancy, growth, lactation) and the diet isn’t adequate, you can use a mineral and protein supplement.

On the vitamin front, you’ll want vitamin E, although supplementing Bs is a wise move during pregnancy.

A few final notes in reference to the insulin resistance. If you need additional calories for the mare when she is lactating, beet pulp with 2 oz. of rice bran added per lb. of beet pulp (dry weight, not soaked) is the safest source of supplemental calories.

Pregnancy can cause insulin resistant, even in mares that are normal to begin with, so following this mare’s insulin every two months or so would be wise. Even some hays are too high in sugars and starches for insulin-resistant animals.

If your horses get too fat on hay alone, have the hay analyzed for sugar and starch. The combined sugar and starch level may need to be kept below 10 to 12%.