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RE: [SPAM] Re: [SPAM] Re: [RC] Thumps - heidi

I had a horse that was prone to thumping, but was one of those on which it
meant nothing.  He could be absolutely normal at every perimeter, but still
have that slight tic in his flank.  I controlled it with extra doses of
calcium.

Which will certainly work, if calcium is the issue.  In some horses, the
problem seems to be magnesium.

In researching some of the reasons this particular horse was prone to
thumps, I came up with some interesting information.  One of the very well
known Endurance vets told me this horse had a large heart for his body size.
This was a very small horse, less than 13.3.  It seems to me since the nerve
in question runs near the heart and fires in rythym with it, that an extra
large heart in a smaller body cavity would be more likely to cause thumps as
the nerve would be positioned closer to the heart.  Is this false reasoning?

I suspect so.  The nerve runs right across the heart, and the heart
discharges an electrical potential with each beat.  The size of the
heart really has nothing to do with it.  Think of the nerve instead as
being like an electrical wire.  If there is a hole in the insulation,
the wire will short out.  The problem is with the myelin sheath
insulating the nerve itself--not with any sort of anatomical size
differences.

Another factor that I felt contributed was, this horse was raised in an area
where the grass is very high in calcium.  Cows pastured in the area often
develop milk fever in the spring due to the high level of calcium in the
soil.  I was given this information from a local large animal vet who
treated these cows so I assume it is accurate.  I know when a horse is given
an excess of calcium, his system loses the ability to source it from his
skeleton which I believe is what the normal horse does under stress. So it
stands to reason if a horse was raised in an area with an over abundance of
calcium available in the grass, his system is probably not well developed to
pull calcium from his bone.

This ability usually comes back when the diet is corrected, though. 
This scenario could certainly be a factor as long as the horse is on
the improper diet--provided his phrenic nerve is susceptible to the
problem.  This seems to be as much genetic as anything.  Horses that
are not going to thump won't do it no matter how bad the diet or how
badly they are overridden or dehydrated.  Horses that are prone to
thumping will do so with very little provocation.  And there are all
"shades of gray" in between.

I participated in a study conducted by Dr. Nagota back in the '80's.  He was
researching calcium levels and how they related to thumps.  At a 105 mile
ride in Ohio, blood was drawn from horses participating in the study 6
different times throughout the ride.  This particular horse finished that
ride in 3rd or 4th place so I was not riding conservatively.

After the ride was completed and all the data collected and reviewed, Dr.
Nagota called me as my horse was the only participant whose calcium levels
stayed stable or even elevated a little throughout the ride.  Since this was
inconsistent with the results from the other horses, he wanted to know why.
The answer, of course, was the extra calcium supplementation I was doing.

But did the other horses thump?  This sounds like an interesting
project, but unless one has already determined that a given horse is
prone to thumping, I don't think it has much application across the
board to other horses.  I've seen too many horses "clear off the
charts" that don't thump, while others thump with very little
variation.

The only time this horse was ever pulled from a ride for thumps was at the
World Championships in Front Royal.  A Swedish rider had leased him and did
not follow my instructions on administering calcium during the ride.  The
horse was thumping slightly at 60 miles, but was absolutely normal in all
other perimeters.  Had we had another 15 minutes in the check, I could have
eliminated the thumps, but as I was unable to administer the extra calcium
until the check and he'd had none for 60 miles there wasn't enough time to
get the thumping under control.  Therefore, he was pulled.  The rider could
not have continued any way.  She was in far worse condition than the horse,
but the horse could have finished easily barring other unforseen events.

Sounds very typical of a horse that will thump with very little
variation--and as you've found out, some of these individuals can be
controlled by very careful e-lyte regimens.

One other thing of note, at a convention where Valerie Kanavy was a guest
speaker. During her presentation, she talked about horses that recover to
extremely low  pulse rates, stating, that in her experience, these horses
often have issues in other areas.  One of the issues she mentioned being
thumps.  My horse had extremely good recoveries under extreme conditions.
He was often recovered to 32/36 BPM at a vet check very quickly.  I wonder
if the large heart may have contributed to the low recoveries and the
thumping as well.

I'd have to disagree.  I've seen thumpers in all sorts of pulse
brackets, and have seen far too many low pulsing horses that NEVER
thump to think that there is any correlation.  Yes, the large heart
will contribute to the low recoveries--but as I already stated, I think
it has nothing whatsoever to do with the thumps.  Just coincidental
traits that in this case happen to occur in the same individual.

Heidi


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