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. 
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14 Responses to Feeding HYPP Horses

  1. Patricia Baring says:

    So what Nutrena feed do you recommend for an N/H HYPP horse?

    • Gina T. says:

      Hello Patricia, Thanks for the question! Our lowest potassium feeds that we recommend for HYPP horses is XTN or Vitality Ultra. XTN is 12% fat and high in calories. Vitality Ultra is 10% fat and high in calories.

      Higher fat and calories allow you to feed less than other feeds, and this can lower total potassium as well when you can feed less to maintain body condition. These are textured feeds and textured feeds tend to be lower in potassium then pelleted feeds. We have several halter horse farms that use these products for their show horses with HYPP. For pelleted feeds, SafeChoice Original can be a good choice if the horse is N/H and doesn’t have many episodes. We do not recommend SafeChoice Original for horses that are H/H and/or have severe or many episodes. Some horses on acetazolamide have done well on SafeChoice Original. It really depends on the individual horse and the severity of the episodes if any and management is key for HYPP horses as well.

      Keep in mind as well that it will also depend on type of hay you are feeding and percent potassium in hay.
      Thanks ~ Gina T.

  2. Leeann says:

    We have raised hypp n/h horses for over 16 years. We have never fed them any differently than the n/n horses and never had any problems. Even our foaling mares are fine. We feed pellets, oats, alfalfa and coastal. Too much bad publicity out there for these horses.

    • lisa says:

      i’m glad you haven’t had any issues. here comes the but, I didn’t either I’ve had my 2yo since he was 9 months old when I didn’t know his hypp status. he was on my growing plan of all the alfalfa he could eat and a 14% 6% fat ration . he started showing signs of attacks with his 3rd eyelid showing and roaring breathing I would give him karo and he would get better. after a couple of these I put him on acetazolamide and added salt . three months ago he had a full blown falling down dog sitting attack. I had had him on oat hay and a small amount of alfalfa , after that I doubled his ace and cut out alfalfa and he had another attack. at this time I now have a useless horse, pretty but useless no trainer will take him to ride due to the unpredictability of the attacks. moral of the story is that just because you haven’t had an issue doesn’t mean you won’t .

  3. lisa says:

    sorry, he didn’t show symptoms til he was around 18 months old.

  4. Denise says:

    I have a n/h mare who’s 7. Didn’t know her testing till after I bought her. Worst thing is I loved this mare well still do. Had no problems ever with her and now I scared to ride her and she is suck a good mare. I had a gelding have a heart attack on me and went down. Dead. Totally did t see that coming. Had another fracture his seamoid bone while riding. A girl friends mare snapped her leg riding her. I just with someone would shed some positive light because I feel like I have been handed the death sentence now.

    • Gina T. says:

      Hi Denise – Sorry to hear about your run of bad luck! We would suggest following the guidelines in this blog post, and also working closely with your veterinarian to manager her condition. Many, many n/h horses have led successful careers and lives with proper management. Good luck! Gina T.

  5. Laura Molloy says:

    I have a 7 yr old HYPP N/H mare. I have owned her since she was 3. No signs of attack until I started pushing feed/hay to get her ready for a horseshow. She started sweating,listless and signs of attack. Vet took blood samples and confirmed.she now exhibits withdrawn, weaving to the point of trance like state ,restlessness after eating.this happens, almost daily and after she eats. I feed dry cob, orchard grass and small flake of alfalfa twice a day. In summer, she only gets grass hay and still exhibits signs. She is such a sweet mare, I don’t want to let her go. What can I do?it doesn’t seem to matter what she eats, she exhibits these signs. I also keep karo on hand .

    • Gina T. says:

      Hello Laura, Thanks for the question. The big key to diets for HYPP horses is low potassium. This means less than 1% in total (hay + grain) diet and no more than 30g potassium in any given meal.

      The horse should be turned out as much as possible and/or placed on a regular exercise program. Feed oat grass or grass hay but NOT orchard grass hay, which is high in potassium. You can get your hay tested for potassium content from your hay supplier or local extension office. Other consideration are do not feed electrolytes containing potassium, and avoiding feeding high levels of soybean meal. Soybean oil, canola oil, cane molasses or bran mashes as they may also be high in potassium.

      We would recommend straight oats, grass hay and a vitamin mineral supplement for your mare.
      Thank you ~ Gina T.

  6. Pat baring says:

    I’ve had my n/h for 4 years now. He’s had 4 episodes.
    1. When I first got him and the vet gave anesthesia to float his teeth and he went down. I didn’t realize he was hypp til then.
    3 at home, 2 mild and 1 bad. He only gets safe choice original and coastal hay. As long as I keep him on that and turned out he does good.

  7. Clarice Rinard says:

    I try to minimize the potassium in my HYPP mare. I just bought dry COB of a new brand and its label says it contains Potassium Bisulfite as a preservative. Should I avoid giving this to her?

    • Gina T. says:

      Hello Clarice,

      Thanks for the question! You don’t really want to focus on the specific ingredients that are the source of the potassium in the case of HYPP horses, but rather focus on the total potassium in the feed, and then in her overall diet, using the formula shown in the blog post. You will want to look at the tag and see if they guarantee the potassium level, and then do the math based on the feeding rate you would give her, to see if she will stay under that 1% total potassium in the diet target level or not. If the potassium level isn’t on the tag, then contact the feed company and they should be able to tell you. Since COB is made of straight grains, which are typically very low naturally in potassium, you may still be OK to use it.

      I hope this is helpful to you! If you have other questions, please let us know! Thank you ~ Gina T.

  8. Kimberly I. says:

    I just received a beautiful, 4yo gelding from my husband for Christmas. When he purchased Jake we knew going into this that he was HYPP N/H. The people we bought him from said he has never had an attack and they were feeding him alfalfa hay in the am and bermuda in the pm. Alfalfa is completely out of his diet since we have had him! We have done all the research on feeds and hay and have him on as strict of a potassium diet as possible. The only problem is that his feet could use a little help. I have tried to find a biotin supplement that would be safe for him, but everything either has linseed meal, flaxseed meal/oil, or soybean meal/oil. Do you have any recommendations? I just want to take care of him the best I can without causing him any harm.

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