No one knew that Dexter had Hyperkalemic Periodic Paralysis (HYPP).

I saw this on FB today… and thought it was very interesting.  I don’t have Quarter horses, but I have heard of this disease.  Also, I was interested how/why Karo Syrup helps, so I did some research on feeding a horse with HYPP.

Thank you, Amanda, for sharing your story!


Amanda Stover
3d  ·
I had one of the scariest and most upsetting events of my horse career happen this past Saturday, and if you are involved with horses (especially Quarter Horses) you need to read this post. I took Dexter to our first show of the season at Maffitt Lake this past weekend. It started out great.
We schooled Friday over fences and he was phenomenal—leaping over flowers, gates and boxes like they were nothing and even getting lead changes. Saturday he was in great spirits, and we had two under saddle classes where he took 3rd both times in huge classes. Then as I waited for my first jumping round, Dexter started to shiver in his neck and sides. We had NO IDEA what was going on so asked him to keep walking, and then for a trot to see what was up. He complied. Then I asked for a canter and he collapsed underneath of me.
His entire back end went out and he crashed to the ground. I rolled out and away from under him and turned to see him frantically trying to lift his body with just his front legs and failing. His his hind legs were paralyzed.
The amazing professional crew at Maffitt acted fast and worked to hold him down so he didn’t injure himself. Vets were called, and we stood and helplessly watched as the paralysis moved to his front legs, too, and my beloved horse lay in what appeared to be rigor mortis. His pulse dropped, his heart started skipping beats and his eyes rolled back in his head. He stayed that was for thirty minutes and then, like nothing had happened, popped up and started grazing.
When the vets arrived, he was identified as having a genetic disease only found in Quarter Horses: Hyperkalemic Periodic Paralysis (HYPP). This is a disease that if the correct low-potassium diet is not fed, can result in paralytic attacks and heart attacks resulting in death if not managed.
I am beyond thankful that Dexter’s first attack happened when I was on him and not one of my children.
I am thankful for the outstanding equestrian crew at Maffitt for acting fast, pulling cars into the arena to block people from seeing him laying on the ground, providing a secluded space for him to recover and the vast wealth of knowledge. Thank you Kyle, Emma, Jessie, Maddie and Dr Hoffman.
Thank you to my barn mom friends Dawn Taylor Jennifer Ried Sara Chung Hannapel and Heather Huntoon for getting Caleb and Joey away so they didn’t sit and watch the disaster, your hugs, and making sure I had food and water as my world fell apart.
And thank you Phil Stover for holding me up while I hyperventilated when we thought Dexter was dying in front of us, standing by my side as we waited for the vet and watching him to see if he would choke or have a heart attack after the episode, and helping me process what this means for the future.
Going forward, I am optimistic we can control this disease with diet and medication.
But if you have a Quarter Horse or know someone with a Quarter Horse, know this disease is out there and get them tested for HYPP. Dexter WAS tested AND tested positive as a foal, but I didn’t know. I didn’t know about this disease and my frustration and sadness realizing if I HAD known this could have been prevented is overwhelming. Do your research so when you buy a horse, you know the questions to ask. And always have Karo Syrup on hand. ????


I found this on the LMF horse feed website (no affiliation, I wish!).  Click here to go to the original article.

The most important management practice for HYPP positive horses is to limit the dietary intake of potassium to less than 1% of the total diet. The largest source of potassium in the diet of a horse is hay. Forages can contain over 3% potassium, factors such as moisture content, stage of maturity and variety (legumes contain more than grasses) all effect forage potassium content. Grains also contain potassium but at a lower rate usually less than 0.5%.

When developing a feeding regime for these horses grass hays or pastures such as Bermuda grass, prairie hay, or timothy should be used as a forage source instead of legume hays such as alfalfa. The use of cereal grain as a major portion of the diet will reduce the potassium concentration of the diet. Beware of commercial feeds containing high amounts of molasses, soybean meal, or dehydrates alfalfa as these all have relatively high potassium concentrations (greater than 2%).

Dietary adjustments include (1) avoiding high potassium feeds such as alfalfa hay, brome hay, canola oil, soybean meal or oil, and sugar molasses and beet molasses, and replacing them with timothy or Bermuda grass hay, grains such as oats, corn, wheat and barley, and beet pulp; (2) feeding several times a day; and (3) exercising regularly and/or being allowed frequent access to a large paddock or yard. Due to the high water content of pasture grass, a horse is unlikely to consume large amounts of potassium in a short period of time if kept on pasture. If the horse is experiencing problems on its present diet, it is recommended to feed a diet containing between 0.6% and 1.5% total potassium concentrations.


I didn’t understand how Karo Syrup helps … because Karo Syrup is a source of potassium.  And, I thought they weren’t supposed to have a lot of potassium.   I was confused.

So I reached out to Amanda and this is what she said:

“It’s my understanding the horses with HYPP have trouble balancing the sodium and potassium in their cells. During an attack, too much sodium enters the cells and pushes the potassium into their bloodstream. The glucose in the Karo syrup binds to the potassium and the cells allow the glucose/potassium mix into the cells and stops the attack. Thanks for reaching out.”

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2 comments have been posted...

  1. Bunny

    What a terrifying experience. Wondering if AQHA horse owners that don’t know their horse’s history if testing as an adult horse is available?

    From a feed standpoint, given that Quarterhorses are the most popular horse breed in the US, and given that so many horses are terribly allergic to all soy products, the best thing the horse feed producers could do is stop using soy products in their feeds. They use it as a cheap source of protein so they can increase their profit margins. Many of the national and even regional horse feed manufacturers will not disclose their feed ingredients on their websites and will flat refuse to answer pertinent questions via email or phone and tell you instead to “go read the feed tag at the retailer because every state has different ingredient disclosure regulations.” While that is indeed true, it’s problematic to have to go to a variety of authorized retail feed dealers and spend hours reading feed sack tags. Best to try to source locally produced feeds and self-educate as much as possible. Note also that taking a deep dive into canine nutrition contraindicates soy products for dogs too – a lot of allergic reactions and also some research is underway regarding an osteoporosis effect on dogs fed products with soy as a major ingredient. The only way these manufacturers who value profit over the health of the animals they profess to “love” will stop piling on the soy is if consumers speak out loudly and at length about their displeasure. Just sayin’.

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