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.
