IMPRESSIVE: What we should all know about HYPP!!!

    When it was requested that I do an article on Impressive and the 
problems with HYPP, I was really hesitant. For one, I was bound to hurt 
someones feelings, and for two, I could conceivably get the old tar and 
feathers. Both thing I really dont like, but, since I am really brave 
(or really stupid) I decided to jump in with both feet.I also wanted 
to learn more about this myself and felt that I could as I researched 
this out. Boy, what an eye-opener this has been! Now I am really glad 
that I did this, though I can almost smell the tar heating up.
    It seems as though all horse folks have some prejudice, though some 
may not be aware of it themselves. I know that personally I have a strong 
prejudice against non-working horses of any breed. I dont mean horses 
that are someone's pet either. I mean halter horses (yep, distinct smell 
of tar on the breeze). Unless one is raising horses to be sold by the 
pound, I can see no point in having horses that are only shown at halter. 
Thats for beef cattle! My feeling is that a halter class should only be 
allowed when a horse has qualified by placing in a performance event. 
Im just not a "feed-em and lead-em" person. I like horses that are 
athletes.(If I hold my head just right I can hear the feathers being 
plucked). So with this confession made, I will commence with my  article.
    Firse of all HYPP is the short version of Hyperkalemic Periodic 
Paralysis. It is a muscular disease that affects both horses and humans. 
HYPP was first diagnosed in humans,and later; in horses of Impressive 
blood. It is a heriditary gentic defect that causes unpredictable attacks 
of paralysis which, in severe cases, can lead to collapse and sudden death. 
The cause of death in this case is usually cardiac arrest and/or 
respiratory failure.
    An attack involves involves episodes of muscle tremors which appear 
as generalized or localized shaking, trembling, and weakness. These 
attacks are occasionaly accompanied by respiratory noises caused by 
paralysis of the muscle in the upper airways (larynx and pharynx). In 
very mild attacks muscle tremors may only be detected by an experienced 
clinician doing actual testing for HYPP.
    There is quite alot of difference in episodes that horses experience. 
Homozygous horses are more severly affected than heterozygous horses, 
though none of my research revealed why. Also, why some horses are 
dramtically affected and others hardly affected id still being investigated. 
Unfortunately, the level a horse is affected has nothing to do with how 
inheritable this defect is. Either extreme is equally capable of causing 
a severe effect in the offspring.
    This genetic defect that causes HYPP involves the muscle and occur 
when a disruption of a protein called sodium ion channel, a tiny gateway 
in the membrane of a muscle cell, happens. At this time the channel's normal 
opening and closing is disrupted and an uncontrolled sodium influx occurs. 
This in turn alters the voltage current of muscle cells, causing uncontrolled 
muscle twitching and extreme muscle weakness. As a result of these 
interruptions, potassium leaks from the inside of the muscle cell and 
therefore, into the bloodstream, thus raising the blood potassium 
concentration. Potassium is an important electrolyte and is vital for the 
normal function of the muscles and nerves. In fact, every cell in the body 
contains potassium and it maintains the cell's volume and electrical activity.  
A horse's diet normally contains high levels of potassium,and pasture grasses 
and hay are providers of a high percentage of your horses's dietary need for 
potassium.  Regulation of potassium is complicated and is regulated by 
hormones produced by the kidneys, adrenal glands, thyroid, and pancreas.  
Normal horse excrete excess potassium in their urine. Studies of HYPP 
positive horses found that potassium levels were normal, however muscle 
function in these horses was a different matter.
     In earlier studies of HYPP, abnormalities in skeletal muscles was found 
in affected horses, and more specifically, spontaneous activities from muscles 
with no stimulation. The affected horses muscles are hyperexcitable(overly 
excitable), and even when the horse appeared normal, in between attacks, the 
abnormalities were repeatable. The abnormalities even occured when the horses 
were under general anesthetic and/or nerve blocking agents. This provided that 
it was indeed the muscles that were abnormal.
     Some horses are thought to be suffering from "tying up" syndrom (or Monday 
morning sickness, as the old timers called it), during the attack, as some 
symptoms are very similar to this malady. However, the HYPP horses seems to 
experience no actual pain during an episode, unlike the horses that is tying up.
A horse that has suffered tying up will also have residual muscle soreness, 
stiffness and weakness after an episode. The HYPP horse has no discomfort after 
an episode. Also, unlike a horse who is tying up, the HYPP horse will benefit 
from forced excercise (providing he hasn't collapsed of course).
     Young horses seem to suffer more frequent episodes of HYPP though the 
common consensus of experts is that the younger horse suffers more stress in 
unusual situations, whereas an older horse with more experience is less anxious, 
so, it is only the stimuli of stress that causes the problem.  Any new or unusual 
experience can bring on an attack.  One can learn to manage the stress in their 
horse's life and help to prevent the episodes as well,so,HYPP is, to a degree, 
something that can be dealt with, with the help of a good veterinarian and your 
own knowledge concerning your horse.
     The genetic defect that causes HYPP is a natural mutation. Mutations occur 
constantly though most do not survive. However, the one that causes HYPP produced 
a functional, though altered, sodium ion channel.
     Many people, falsely assumed this mutation occurred as a result of 
inbreeding.  As many of you know, Impressive is an intensely linebred horse. 
He has more Three Bars(TB) in him than nearly any horse in Quarter Horsedom.
(Nearly more than old Three Bars himself!!) His sire was a son of Three Bars and 
his dam a paternal granddaughter and maternal great-granddaughter of Three Bars.
This sounds like alot of marryin'amongst cousins, and it is, but, it is not the 
cause of the HYPP cropping up in the Impressive line.  It is the result of a 
horse having this mutant gene and a heavy musculature. It became widespread when 
horses were bred with the idea of attaining excessively heavy muscling, and that 
was very easily done with the Impressive line. However, that doesn't mean that 
all heavily muscled horses will have HYPP. It also doesn't mean that it can't 
happen.
     My research turned up the name of a deceased broodmare that produced HYPP 
in her offspring, and neither her, nor her foals were related to Impressive. 
Her name was Cloudy Review, AQHA number 1603536. She also was an intensely 
linebred horse of heavily muscled line of horses. She was sired by Sheik's 
Review and out of Cloud Skipper. She traces to Skipper W three times, Slipalong 
Weiscamp four times, Santa Maria two times, Nick S four times, and Starduster 
twice. Yes, she is pretty tightly bred. Mr. Weiscamp did this in his program 
to achieve the extreme muscling that is found in his horses and it has been 
continued by breeders trying to acheive the same thing, to a greater extreme, 
in their own programs.
     The inheritability of HYPP is certain, though. If you have a horse with 
HYPP, it will pass it on to it's offspring. Breeding trials done at University
of California at Davis (UC Davis) determined that it is equally inherited 
through both male and female horses. It is ingerited from generation to 
generation and IS NOT DILUTED OUT. Some breeders are assuming it will dilute out 
if you have a horse that is only distantly related to Impressive, but, they are 
absolutely wrong in this. The only way to be sure is to test your horse.
     According to UC Davis studies, breeding an affected heterozygous(N/H) horse 
to a normal(N/N) horse will result in 50% carriers of the gene. Breeding an 
affected homozygous(H/H) horse will result in all the offspring carrying the 
genedefect, regardless of the other parent.
     Normal(N/N) offspring can safely be bred without fear of the defect and it 
will not be inherited. So, if breeders would only breed N/N horses, they could 
still enjoy the benefits of the Impressive line without fear of creating more 
HYPP postive horses. Because HYPP is inherited as a dominant condition, it is 
being spread to other breeds such as Paint and Appaloosa horses. Again, it's the 
quest for the excessive muscling hat created the problem. In reality, if ethical 
standards were adhered to, HYPP could easily be bred out of the industry.
     To add a personal opinion, HYPP positive horses should be in the same 
category as crytochid and parrot mouthed horses, and only be registered as a 
gelding or a spayed mare. I also feel that if the average breeder would have 
come up with a line of horses with HYPP, those horses would probably have been 
eliminated from the registry and not encouraged by continuing registry of 
affected individuals. (Man I can hear the tar bubbling!) Obviously, there is 
a huge amount of money to be made in the breeding of the world beating halter
horse, so nothing has or probably will be done to enforce the elimination of
affected horses. It is a shame too, as the HYPP monster lurks around the corner 
of every horses known to be of Impressive blood, even if they are N/N tested 
horses.
     It is so simple to determine if a horse is HYPP positive and it is actually 
quite inexpensive. Breeders would be wise to have any mares or stallions that 
could possibly carry the gene tested and then they can promote their horses and 
assure buyers that they are N/N horses.
     I have not personally ridden an Impressive bred horse, but, have many 
friends (at least I had friends before I wrote this...) who ride and use close 
up Impressive horses. They range from pleasure horses to capable ranch horses, 
and are appreciated greatly by their owner. I also know of a PRCA pickup man 
that uses many Impressive bred horses to pick up broncs at rodeos all over the 
nation and many times at the NFR. He is sure enough ahorseback and they are fast 
and very handy at this gruelling equine profession. So, the Impressive horses 
are athletes, their pedigree says they should be, but you need to select a horse 
that has been tested to determine HYPP negative status. Don't even go look if 
the horse hasn't been tested.
     A simple test(blood or mane roots) can be performed to detect the defective 
gene carriers the HYPP possess. For a $50 investment, UC Davis can perform this 
accurate and reliable test on any horse. The AQHA, (who should have their wrists 
slapped for allowing this mess to continue) can give you detailed information on 
how to perform the test and how to attain the kit. I encourage anyone breeding 
and/or selling Impressive bred horses to get it done, and furthermore, if they 
have a positive horse, put a stop to the further breeding of that individual and 
make this condition known to any potential buyers. Knowing is half the battle.
     So, now that I probably have hurt some feelings and will no doubt be tarred 
and feathered, I will close by saying that there is encouraging news about 
Impressive's line of horses, and if you are careful, you can own an Impressive 
horse with no worry about this disease.
     By the way, does anyone have a good way of removing tar from clothing and 
hair? How 'bout feathers....

                                    Written by Jan Swan Wood
                          Taken from the Midwest Horse Barter April/May Issue


    I'd like to thank Jan for her article and add one thing myself.The American 
Quarterhorse Association could put an end to this whole mess so easily by simply 
forcing the spaying and gelding of positive horses.They say that their primary 
goal is to better the breed yet, they continue to let this problem destroy and 
divide the industry on account of a few politically powerful (and more importantly) 
rich people who think they need to show these defective horses. I hope and pray 
just one person who makes these decisions reads this article and my comments
because I say to you- Quit being afraid of making one person angry and start 
worrying about the thousands of breeders you are hurting shame on you for letting 
this go on. None of you have any business being in charge of this organization, 
and you know there are a lot more people that feel this way than there are that 
like to breed positive trash horses.The Quarterhorse is America's breed and should 
be something to be proud of. Promoting the breeding of positive horses is shameful, 
fix this problem, and fix it now, before the American Quarterhorse Association is 
nothing more than a distant memory. Anyone who agrees with this opinion please let 
the Association know how you feel. Let your opinion be heard, dont sit idly by 
while our livelihood is destroyed by a few foolish individuals.
                                   
                                    Written by Rodney W. Burgerhoff
                                    Quarterhorse Breeder