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Feeding HYPP Horses

HYPP horses need low potassium diets when compared to “normal” horses – less than 1% potassium in total diet including hay + grain.  But, a percentage in a feed is really only a percentage and doesn’t tell you what you really need to know – which is, how much potassium your horse is actually getting in the total diet.  This number will depend on the percent of potassium in each feedstuff, and how much of each feedstuff is being fed.

Hay Selection:  Hay makes up the majority of the diet so typically contributes the most potassium. It’s best to have your hay tested if possible, but if you can’t do that, keep in mind the following:

  • Oat hay and grass hay are the lowest in potassium
  • Orchard grass is high in potassium so stay away from that.

Feed Selection:

  • Textured/whole grain based feeds tend to be lower in potassium then pelleted feeds, since whole grains are naturally low in potassium, where some ingredients used in pellets tend to be higher potassium sources.
    • “Sweet” feeds may or may not use a lot of molasses, which is high in potassium. The “wetness” of a sweet feed may come from vegetable oils rather than molasses, so don’t automatically rule sweet feeds out.
    • Some pelleted feeds can be a good choice if the horse is N/H and doesn’t have many episodes, but may not work for horses that are H/H and have severe or many episodes.
  • Higher fat and calorie feeds may allow you to feed less, and this can lower total potassium as well when you can feed less to maintain body condition.
  • Do not feed electrolytes containing potassium.
  • Do not use high levels of cane, molasses, or bran mashes because they may be high in potassium.

Doing the math: To determine how much potassium is in your HYPP horse’s total diet, you’ll need to do some good old fashioned math!

To check for total potassium in the diet:

(Pounds of hay x percent potassium in hay) + (pounds of grain x percent potassium in grain) / total lbs of feed

Example: If you feed 15 lbs of hay at 1% potassium and 6 lbs of grain  at 0.8% the calculation would be:

((15 x .01) + (6 x .008))/21 lbs of total feed = 0.942% potassium in total diet

From this example, the horse should do well on this diet.  If the horse can maintain body condition on less hay or grain, or if the hay tested lower in potassium, then that would be less potassium in the total diet as well.

Other Considerations:

  • Starch Intake: It is a misconception that HYPP horse need low starch.  They actually need sufficient starch as a source of glucose, because glucose stimulates the release of insulin and this promotes potassium uptake by the cells.
  • Management:  HYPP horses should be turned out as much as possible and/or placed on a regular exercise program.