DSLD: a hereditary disease

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Lord Helpus
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Sat Mar 17, 2018 5:14 pm

I am posting in the breeding forum because DSLD/EPSA is a hereditary disease which affects TB's (as well as a number of other breeds). It is irreversible and inevitably results in euthanization.

You may well ask "Why have I never heard of it and how can I prevent a horse that I own from passing it on"?

You possibly have never heard of it because the early symptoms are similar to other diseases. Also, the early symptoms often are varied and they come and go. Why is this important in TB's? Because DSLD may well contribute to those catastrophic breakdowns that are so devastating.

DSLD [Degenerating Suspensory Ligament Desmitis] is a systemic disease of the connective tissue of the horse. It mostly shows up in the suspensory ligament, which is made up of nuchal (pronounced "nukal") tissue. Nuchal tissue appears in other places in the body (specifically in the neck, where its job is to stop the stretching of muscles whose job it is to lower the head (my simplistic understanding). A horse's neck would continue to fall forward unless there was a nuchal ligament which comes into play when the neck has reached its maximal appropriate extension. At that point, the nuchal ligament takes over; the neck muscle stops working, and the head and neck lift again.

DSLD is a horrible life sentence because, in horses afflicted, the fibers of the suspensory get stringy until they begin to detach from the lower hock joint.

Since the symptoms come and go, and move around, and are often subtle (a "hitch in his gitalong" which gets better, then comes back, etc) it is often overlooked or misdiagnosed. The one indisputable system is the dropping of the fetlock until it is horizontal. At that point, the suspensory is no longer doing its job, and there is nothing left to do.

What can an owner or breeder do? 1. Since it is heredity, a breeder should be very leery about using a mare or stallion who has less than optimal pastern angle, or whose immediate ancestors did. 2. If a horse has intermittent, mild lameness (with or without heat or swelling), talk to your vet ASAP about the possibility of DSLD.

I wonder just how many catastrophic breakdowns, which are caused by a blown suspensory (or which are caused by broken bones which might have been snapped by an iffy suspensory which could not withstand the rigours of racing at high speeds.

Until recently.trainers, and even vets, did not suspect DSLD early enough to take the horse out of work before he is left lying flat on the track.

The only way to prevent this is to ask questions, because stallion owners certainly will not say anything. Be wary of horses who sire unsound progeny (or that unsoundness runs in the family). It may have nothing to do with DSLD, but it is worth thinking about using the stallion.

Mares with dropped fetlocks may just have had a lot of foals, and the collapsing fetlocks are the result. But younger mares should not have them.

Believe it or not, I know a lot more than I am covering here. My heart horse, who is beautiful, talented and so personable that he makes me smile has it, so I have spent hours researching it. He is 6. And will be a pasture pet until he has no quality of life --- when he will be euthanized. The average time between diagnosis and euthanization is 2 years. :(
BaroqueAgain1
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Sat Mar 17, 2018 6:02 pm

Is there a diagnostic test for the disease? Can it be found in blood samples, or would it require a DNA test? :?
Lord Helpus
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Mon Mar 19, 2018 12:47 pm

There is a new test which is still in the testing stage. I have Goober doing it; I should have answers this week.

A pathologist in Georgia noticed that the nuchal ligament in horses who were necropsied, had nuchal ligaments which matched the nuchal ligament in living horses with suspected DSLD. So the lab at Georgia State (or Georgia University?) has started a test to see if the disease can be correctly diagnosed in living horses. So far the test is looking very hopeful.

If the test is viable, then the hope is that these living horses will be diagnosed early enough that they will be candidates for suspensory surgery, or who will be retired from their job as breeding stallions

The problem with this plan is that it is rare that horses will have the test in the early phases of the degeneration.

But, since DSLD is hereditary, perhaps owners of from lines who have offspring with early lameness will use the test. I am thinking of Unbridled's Song, but I do not want to defame him --- he is just the KIND of horse (reputation for unsoundness in his progeny) who should be tested.

Then, with the goal of not breeding to such a stallion, the disease will be eliminated from the breed. Sadly, people are happy to breed to unsound horses. :(
TBird
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Joined: Thu Sep 19, 2013 9:09 am

Mon Mar 19, 2018 1:50 pm

Yes, hereditary--in warmbloods.

It seems a huge stretch to try and include Unbridled's Song here when the unsoundness his offspring displayed had nothing to do with the symptoms of DSLD.
aethervox
Posts: 191
Joined: Wed Sep 18, 2013 11:48 am

Mon Mar 19, 2018 3:18 pm

DSLD/EPSA affects a horse systemically, i.e. throughout the body, and affects the aorta and coronary arteries, per article at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1459153/.

Could this be a cause of the 'heart attacks' that cause young horses to suddenly collapse and die?

Just a thought.
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Treve
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Mon Mar 19, 2018 7:25 pm

TBird wrote:Yes, hereditary--in warmbloods.

It seems a huge stretch to try and include Unbridled's Song here when the unsoundness his offspring displayed had nothing to do with the symptoms of DSLD.
Considering warmblood is a term/type rather than a breed, with most having open studbooks (I believe Trakehners are the only exception and the only non-Traks that can be approved are Arabians and Thoroughbreds... ie fixed gene pools) it is safe to say that if it is hereditary in them, then it would be hereditary in a closed gene pool like Thoroughbreds, Arabians etc. If it were found to be hereditary in just one closed gene pool that would be a different matter.

Lord Helpus was pretty good about specifying that they weren't including Unbridled's Song as a horse that needs to be tested (anyway... bit late for that) rather he's a recent, famous example of a stallion whose offspring seem to be reputed for unsoundness. And that TYPE of reputation should give one reason to at least test for DSLD. I don't see how that's a stretch, especially since LH specifically said they didn't want to defame Unbridled's Song and weren't accusing him or his offspring of having DSLD or being test candidates.
A filly named Ruffian...

Eine Stute namens Danedream...

Une pouliche se nommant Trêve...

Kincsem nevű kanca...


And a Queen named Beholder
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Ridan_Remembered
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Tue Mar 20, 2018 7:05 am

In an announcement by Taylor Made just in the last few days about Unbridled's Song being 2017 Leading Stallion (thanks mostly to money won by Arrogate in the Pegasus), they even said he had a reputation for producing unsoundness in his offspring. Whatever the cause, if one stallion's get have a higher than average incidence of unsoundness, then there has to be a genetic component. Whether it's DSLD or other condition would take research, studies, etc., to determine.

Arrogate's racing career was very unusual in that he was an average racehorse until he suddenly became a world beater for 4 races, then became average again. Why? Who knows, but if I was a breeder, I would not send a mare to him until his first couple of crops were racing.
Ziggypop
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Tue Mar 20, 2018 4:26 pm

Ridan_Remembered wrote:In an announcement by Taylor Made just in the last few days about Unbridled's Song being 2017 Leading Stallion (thanks mostly to money won by Arrogate in the Pegasus), they even said he had a reputation for producing unsoundness in his offspring. Whatever the cause, if one stallion's get have a higher than average incidence of unsoundness, then there has to be a genetic component. Whether it's DSLD or other condition would take research, studies, etc., to determine.

Arrogate's racing career was very unusual in that he was an average racehorse until he suddenly became a world beater for 4 races, then became average again. Why? Who knows, but if I was a breeder, I would not send a mare to him until his first couple of crops were racing.
I agree. Couldn't believe my eyes wben I read Songbird was going to him.
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Treve
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Tue Mar 20, 2018 6:49 pm

Ziggypop wrote:
Ridan_Remembered wrote:In an announcement by Taylor Made just in the last few days about Unbridled's Song being 2017 Leading Stallion (thanks mostly to money won by Arrogate in the Pegasus), they even said he had a reputation for producing unsoundness in his offspring. Whatever the cause, if one stallion's get have a higher than average incidence of unsoundness, then there has to be a genetic component. Whether it's DSLD or other condition would take research, studies, etc., to determine.

Arrogate's racing career was very unusual in that he was an average racehorse until he suddenly became a world beater for 4 races, then became average again. Why? Who knows, but if I was a breeder, I would not send a mare to him until his first couple of crops were racing.
I agree. Couldn't believe my eyes wben I read Songbird was going to him.
It was already unusual enough sending a maiden to a first year stud. I'm still not quite over it, but I just read in an article that Juddmonte is limiting his book on purpose so there's less competition between breeders at the sales and it'll hopefully increase the value of Arrogate's offspring... so who knows what they might've wooed Pope with. Still I don't think they're even a good physical match. And I still think they should've gone with their first gut feeling, Pioneerof the Nile (several other stallions could've been good too of course but I think that would've been a good decision commercially and physically).
I do hope overall they've managed to find mares that will hopefully correct his physical issues because if his offspring have even just a fraction of his talent (I wouldn't say he was necessarily average before the Travers and it's possible he just simply didn't care for Del Mar after at all but who knows) and are sound they're gonna be pretty popular.
A filly named Ruffian...

Eine Stute namens Danedream...

Une pouliche se nommant Trêve...

Kincsem nevű kanca...


And a Queen named Beholder
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Sparrow Castle
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Tue Mar 20, 2018 10:30 pm

Doesn't really shed much light on the details, but Mandy answered the "why Arrogate for Songbird" question in the Winter 2018 edition of Thoroughbred Today (on issuu.com). She basically said her first choice was Tapit but, after she, Wayne (I assume Wayne Sweezey at Timber Town), and their pedigree expert did a lot of research and going to see Arrogate, they made the decision. She said she knows it's a little different to breed that kind of maiden mare to a maiden stallion but they figure if they get a nice foal they'll have a really interesting horse to put on the market.
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