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Muscle tremors in big stock horse

Today my big Paint mare exhibited entirely new symptoms. In her paddock in the morning, she had twitching shivery involuntary tremors in her major muscle groups, haunches, upper arm and neck. I handwalked her out to a holding pen to let her roll, then tried to get her to drink salt molasses water, and they eventually abated. I don’t know obviously if this is first time or if she’s been doing this for a while without me there.

Big muscular Paint, now 17, who has always been slow to warm up and sometimes pissy under saddle but forward once she is warmed up. Needs a rest day at least every 5 days for optimum happiness. Very healthy generally, great feet.

Diet for years has been 15 to 18 lbs of good Timothy in 5 feedings a day. Small beet pulp and Alfalfa mash with a cup of flax and a vitamin mineral supplement. Very enthusiastic with her salt block. Weight is good. No metabolic syndrome symptoms.

This past week, she got Wednesday and Friday off because of rain, got attended turnout and refused to move much in turnout. Thursday and Saturday she was very forward under saddle. Saturday, yesterday, we did a big power march walk 2 hour plus trail ride at home that included about half an hour grazing new spring grass under the powerlines. Today Sunday I was going to trailer out, she was excited to see the trailer, but I cancelled when I saw the tremors.

She did not drink much over night, cold Spring weather. I have recently switched her VMS to a much stronger formula. She has also developed a taste for banana peels and has had one almost every day :slight_smile: for the past week. I will link to the VMS in case anyone sees an obvious imbalance in the mineral ratios.

I’ve honestly sometimes wondered about HYPP or PSSM with her, but never had any concerning symptoms other than slow to warm up. Is there anything else I should watch for? I will talk to my vet about the panel tests when we do teeth and vaccinations.

Here is the new mineral supplement I started last month. We have been slowly working up to about 3/4 the recommended dosage. The product in general is about twice the values of everything in my previous VMS.

https://madbarn.com/product/omneity/

We are in a low selenium region. The hay is not tested. We are on city water so it is low iron.

I am not qualified to give nutritional advice I can’t help there.
Does she have any Impressive blood in her pedigree? If so, or if you are unsure, do test for HYPP.
HYPP horses can go for years with no symptoms. It can be “managed” (to an extent) so the sooner you know, the better.

Sending good thoughts your way.

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We never got her papers so don’t know her breeding, unfortunately. I do know Impressive blood is quite widespread.

I’ve just been Googling, and I should add she seemed unconcerned and in fine form during the tremors. No sweating, no obvious pain, no eye droop etc.

Yes, and it is definitely a presence in the Paint registry.

As you know, textbook cases are just that. I hope HYPP is not the problem, but I’d want to find out for sure because of your horse’s breed and type.

Testing for what is applicable, or the whole 5 panel test, cost about the same, is always a good start for any suspected metabolic issues.

A fellow here had a big, beautiful slow gelding he used in parades and rodeo entrances that was Impressive bred.
That was before HYPP was known.
Once the horse was older, almost 20, he had some “spells”, light ones, of shivering and uncoordinated and he quit riding him.
Later he was wondering if it had been a mild expression of HYPP, as you are now.

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Ok thank you all. I will get my vet to run the full panel. No need to do the Lethal White Overo one, she’s an obvious classic Frame Overo :).

Any suggestions as to management strategies in the meantime? She generally gets daily exercise. I can pull the VMS if it has too much potassium. We can quit the banana peels as treats.

Could it just be a bit of dehydration? This horse gave herself repeated impaction colic one winter/spring from not drinking when the weather changed.

I knew someone who had a big, beautiful paint that had the same symptoms. They were very subtle. Testing is the best way to go.

How disconcerting. Jingles for a simple, treatable diagnosis.

Get the Selenium tested seperately. In a low area, like us, we have to supplement Selenium and Vit E in addition to their Vitamin supplement, to insure our horses get enough Selenium. Low levels can affect many parts of the horse system, reproduction, muscles being the most common and visible in daily life. Do not expect a feed mix to supply enough Selenium and Vit E to a horse, especially if you are not giving the maximum recommended daily feed amount on the bag.

Selenium gets used up easily, sweated off, needs constant replenishing. Without Vit E, horse does not absorb the Selenium, just goes thru the horse.

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We had the same thing happen to a big Paint mare in our barn. Hadn’t been ridden for a week or so, owner hopped on and hadn’t even walked halfway around the arena. The mare kind of acted a little slow and lazy, but her rider quickly figured out something wasn’t right. By the time I got out there, her whole back end was in major tremors and lighter tremors in places along the rest of her body. Vet was called and by the time she got there, the tremors had quit. The one thing we did notice was that she was super, super sensitive along her topline, when she hadn’t been when she was brushed and saddled. Vet checked her over and couldn’t find anything. No Impressive in her breeding. Vet put her on muscle relaxants for a few days, and as far as I know it’s never happened again.

This sounds like some kind of tying-up, Monday morning disease, azoturia, Exertional Rhabdomyolysis (ERM).
We had one school horse and endurance horse start this.
We could tell that is what it was, his urine was dark, showing muscle was destroyed.
He also was not wanting to move.
Once vet attended to him, we kept him on special exercise program and he was fine.

This tends to be so specific, there is no question that is what it is.
When it hits, vet is called right away, horse is obviously sick.
Blood work will confirm or rule that out.

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Hmmm. My mare’s symptoms were very light, just the spasms, and those went away in about 20 minutes. We had a fine quiet ride later in the day. Didn’t occur to call the vet then. I will get a full panel test done when we have our teeth and vax appointment done within the next month.

I did as a precaution take her off her new super powered VMS in case this was a HYPP pottasium reaction, and put salt in her mash, good for both HYPP and dehydration. Her diet is low starch and sugar as it is, and she gets 5 feedings of hay a day, 3 to 4 lbs each, so we’re already within the PSSM recommendations there. I’m going to make sure she gets proper movement even on her days off going forward.

Thanks for all the comments. Sounds like whatever it is could be manageable even if it’s a chronic underlying thing?

The standard panel is a great place to start, but PSSM isn’t as straightforward as HYPP. There are 2 commonly accepted variants of PSSM, but another company tests for several more beyond that. The last I looked into it (several years ago), that company claimed peer-reviewed research was on the way, but I am not sure if that ever actually happened. I am in a couple groups on facebook dealing with PSSM and there is a lot of anecdotal evidence for the additional types.

The company that does the testing for multiple variants is EquiSeq. May be something worth reading and you can decide for yourself if it’s worth pursuing.

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That’s pretty classic HYPP.

I’d want to know that, PSSM (type 1 is the test here) and IMM, and by the time you do those, the full 6 panel may be just a little more, but you can do the cost comparison

I wouldn’t say it’s not PSSM, but just hanging out and having muscle tremors in those places is pretty classic HYPP

@JB thanks! Do you think it’s connected to me starting up a new Vitamin Mineral Supplement that has more of everything?

I’m looking at the label of my old supplement and it looks like it had no potassium at all? Pureform Support One. The link to Mad Barn Omniety is in my original post. We’ve been on it for about a month slowly ramping up to full dosage, were at about 3/4 when this happened. My Googling tells me HYPP horses should have no added potassium so maybe I triggered an underlying condition here?

that’s certainly a possibility. They can have added K, but each thing, and for sure the entire diet, should be below 1.3%.

Could she just have been cold and excited? You mention cold Spring weather and then she saw the trailer. Sounds pretty typical of my guys. They can be just fine and calm as can be in the pasture but as soon as they get put in the first stall (that’s attached to the tack room and where I put the horse being ridden) they tremble (are we hunting? Is it time to GALLOP!?) And if it’s cold on top of it they over compensate and can get pretty shaky.

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It’s possible. It wasn’t that cold though, not freezing. And she had wierd spasms in her neck. Given being a very muscular Paint of unknown breeding, HYPP is a reasonable worry, and an episode can be triggered by stress. If she tests negative then I’ll be inclined to agree with you!

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I just looked up some online videos of HYPP episodes and that all over muscle twitching is exactly what she was doing.