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Managing Shivers

I have a wonderful horse in my barn who has suspected neuromuscular disease, or Shivers. This horse has difficulty backing-up, lifting her hind feet for the farrier, exhibits some muscle trembling and likes to stand in a “parked out’ position. She is a 12 year old mare and has exhibited these symptoms most of her life. She is also one of the most balanced horses under tack, has a terrific jump and bascule over fences and is a genuine sweetheart. I feed Ultium in the barn.

My question, can you advise if I should alter her feeding and/or add a supplement? And, second question, what do you think is her prognosis? I understand this condition will not improve, however, will it progress to a point where she cannot walk/stand and need to be euthanized?

Thank you in advance for your consideration, guidance and opinion. LH, New Jersey

Dear LH,

For those unsure what “shivers” is, classic signs of the disease are trembling of the tail while held erect and trembling of the thigh muscles while a hind limb is held flexed. However, the signs described above are pretty common, too. It’s most often seen in draft horses like Belgians but it also occurs in warmbloods and other breeds. The bad news is that experts don’t know what causes “shivers.” The really bad news is that there is no treatment and the condition does slowly progress over time until the horse cannot stand because of muscle wasting and weakness.

My first advice to you is to be absolutely sure you’re dealing with “shivers” and not some other neuromuscular condition of the hind limbs, as there are plenty:

polysaccharide storage myopathy (PSSM)
• fibrotic myopathy
upward fixation of the patella
• equine motor neuron disease (EMND)
• “stiff horse syndrome”
equine protozoal myelitis (EPM)

Some of these are treatable or at least manageable so make sure an equine veterinarian confirms the diagnosis.

As far as what to feed her, because many horses with “shivers” also have PSSM, some owners have success with a low carb/high-fat diet (check out my article and my blog on this condition). As long as you involve your veterinarian in formulating the diet and make changes gradually, there shouldn’t be any harm in trying this.

And I always recommend Vitamin E for any neurological or muscle condition, because it’s such a great antioxidant specifically for these tissues. The sixth edition of the National Research Council (NRC) Nutrient Requirements of Horses says horses at maintenance need 1 IU (international unit) of Vitamin E for every kilogram of body weight. This works out to 500 IU for an 1100lb horse. For horses at work they recommend twice that or 1000 IU daily. However, veterinarians are recognizing the value of Vitamin E for many of the conditions listed above and prescribing much higher amounts, such as 2,500 IU, 5,000 IU and even 10,000 IU. Fortunately, the NRC says “Vitamin E does not appear toxic to horses even at relatively high intakes.” I still recommend you involve your veterinarian in selecting the most appropriate dose.

Same goes for Selenium, which partners with Vitamin E as a beneficial antioxidant in nerve and muscle tissue. The NRC recommends 1 mg per day (noting that 3 mg per day improved the immune status of mares and their foals) but the window between deficiency and toxicity is much smaller. Therefore, ask your veterinarian to take a look at the hay and grain your horse is getting now and recommend an amount of Selenium (if any) be supplemented.

The only other management advice I can give you is keep her in light, consistent work to try and prevent muscle wasting. Rest appears to benefit some horses but as soon as they are brought back into work signs reappear as badly as before. Stress and excitement do seem to worsen the condition, so try to keep her schedule and environment as consistent and calm as possible.

For more information on “shivers” and other neuromuscular conditions of the horse, I encourage you to visit



Lydia F. Gray, DVM, MA SmartPak Staff Veterinarian and Medical Director Dr. Lydia Gray has earned a Bachelor of Science in agriculture, a Doctor of Veterinary Medicine (DVM), and a Master of Arts focusing on interpersonal and organizational communication. After “retiring” from private practice, she put her experience and education to work as the American Association of Equine Practitioner’s first-ever Director of Owner Education. Dr. Gray continues to provide health and nutrition information to horse owners through her position at SmartPak, through publication in more than a dozen general and trade publications, and through presentations around the country. She is the very proud owner of a Trakehner named Newman that she actively competes with in dressage and combined driving. In addition to memberships in the USDF and USEF, Dr. Gray is also a member of the Illinois Dressage and Combined Training Association (IDCTA). She is a USDF “L” Program Graduate and is currently working on her Bronze Medal. Find Dr. Gray on Google+

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