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Discussion on OC incidence the effects of genetics and size
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Moderator:
DrO
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Posted on Monday, Feb 13, 2006 - 10:38 am:
Everytime they look at osteocartilagenous lesions (let's call it osteochonDrOsis OC) and genetics a fairly strong connection is found. Not surprisingly a positive correlation between height and OC has also been found. The reason this is not surprising is that OC is most often a lesion started by trauma and not necessarily acute injury but just the daily trauma of getting about. Healthy joints repair this trauma back to normal. OC occurs when the repair does not keep up this trauma. The larger the animal, the more daily trauma the joint undergoes. You might think that since the joint is bigger and that this counteracts the larger size of the horse. But as animals get bigger, weight grows at a cube rate while the joint surface grows at a square rate.
The take home message is that when breeding it behooves you to check the OC status of your breeding stock and that bigger is going to be more fragile.
Vet J. 2006 Jan;171(1):147-56.
Factors associated with the prevalence of osseous fragments in the limb joints of Hanoverian Warmblood horses.
Stock KF, Hamann H, Distl O.
Institute of Animal Breeding and Genetics, School of Veterinary Medicine Hannover, 30559 Hannover, Germany.
Factors associated with the prevalence of osseous fragments (OF) in fetlock and hock joints were investigated in a population of young Hanoverian Warmblood horses selected for sale at auction from 1991 to 1998. The study was based on results of a standardized radiological examination of 3127 horses. The prevalences of OF in the two joints were significantly dependent on the date, type and quality of the auction, the region of origin and on the anticipated suitability of the horses for dressage and/or show-jumping. The probability of finding OF increased with wither-height. Furthermore, there was a significant association of the individual sire with the prevalence of OF in both fetlock and hock joints, and of the maternal grandsire with the prevalence of OF in the hock joints. Consequently, both non-genetic and genetic parameters should be taken into account in order to reduce the prevalence of OF in young Warmblood riding horses.
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Member:
Erika
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Posted on Thursday, Feb 16, 2006 - 10:41 am:
Very interesting, Doctor O. I have heard numerous times that horses 15.2-ish are usually the most likely to stay sound. Why then do you suppose this trend toward huge horses? Do they really perform better even at the risk of unsoundness, or is it just aesthetics and fashion? Anybody have any ideas or opinions about this? I don't show, so I don't know the thinking behind the "bigger is better--and lots more expensive" rule!
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Member:
Lilly
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Posted on Thursday, Feb 16, 2006 - 3:02 pm:
Hi Erika,
I wanted to respond to your "why go big" question. I am 5'8" and I ride dressage. Every instructor I have ever had said I should be on a horse larger than 16 hands. I guess my legs are nice and long and just fall right on a big horse. I also feel more comfortable trotting on a large horse. I love a nice long stride. I just retired my horse but we were a great match and he is almost 17 hands. I also don't believe that falling off a 15 hand horse is going to hurt less than falling off a 17 hand horse. I have gotten some massive bruises from little horses  .
Ann
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Member:
Terrilyn
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Posted on Thursday, Feb 16, 2006 - 4:36 pm:
Hi Ann and Erika---
I am 5'10" and prefer 15.1-15.3H horses, no larger. Always have. Like Ann, I've been told that my long legs look just great on TB-type larger horses...but that's not my preference. I am just more comfortable on a smaller, more compactly built horse and for the type of riding I do (nothing fancy, just trails) that's fine with me. Give me a stock-type horse any day!
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Moderator:
DrO
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Posted on Thursday, Feb 16, 2006 - 5:59 pm:
You have to admit a snappy dresser on a snappy 17 hand horse is both a beautiful and impressive site.
Then again to overcome the slightly unsnappy natural demeanor of many of our warmbloods to produce that snap is kinda what a lot of dressage training is all about. I often thought Arab X WB crosses might make dressage a good bit easier in some ways and it looks like they may be sounder but I usually get funny looks when I say it aloud.
DrO
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Member:
Lilly
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Posted on Thursday, Feb 16, 2006 - 9:36 pm:
DrO,
At my barn there is a Polish Arab/Hanoverian cross that is just the prettiest thing in the world. She is almost 2 years old and has already passed the 15 hand mark. Her mother is over 17 hands. The barn manager used a large Hanoverian dam with a smaller Arab sire (Ahmeetz) so that the foal would not be too big. She had previously bred a thoroughbred with a Hanoverian sire and the babies were huge! I would love to have an arab/warmblood cross to call my own.
Ann
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Member:
Parfait
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Posted on Thursday, Feb 16, 2006 - 11:54 pm:
Dr. O.
You are SO cutting edge! They are doing a lot of crosses for our Sport Horse discipline and the horses are way cool. It's a lovely combo of a slower mind and lighter feel...I might even pick up one of those babies myself.
Kerry
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Member:
Erika
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Posted on Friday, Feb 17, 2006 - 8:43 am:
Just an interesting sideline to the Bigness issue. We were in NW China, near Mongolia a couple of summers ago. We rented horses to ride there. Not a one could have been more than 13 hands. Some of the men there were bigger than their horses. Not such a "snappy" image!
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Member:
Christel
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Posted on Friday, Feb 17, 2006 - 9:16 am:
On the other side of the coin, one must not forget how small the cutters and reiners are getting. It seems they get smaller each year while the riders stay the same size or bigger, and those horses are still packing em around.
I remember a dear friend of mine that passed away 5 years ago and he telling me- the older I get the smaller I want my horses- they are easier to get on-
None of my horses even reach 15 hands, one comes pretty close, I am always in awe of those big 17 hand horses as I am not use to being around them. Heck anything over 15 is big to me.
Chris
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Member:
Mrose
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Posted on Friday, Feb 17, 2006 - 10:23 am:
Like Chris, I'm at the point where I like little horses. My knees don't bend enough for me to get on a tall horse; not only am I getting older, but am only 5'3" to start with. I have to use a step stool to get on the stallions. Luckily, they are patient.
I think what a horse can carry has more to do with bone density and stoutness then height. Of course, some breeds are both big and stout, like the draft breeds. I was thinking about some of the mountain pony breeds and the loads they carry.
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Member:
Hwood
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Posted on Friday, Feb 17, 2006 - 11:21 am:
Yes, Sara . . .
Shetlands are can carry up to 2/3 their weight . . . more than any other breed in relation to size . . . and the smaller horses tend to have longer lifespans . . . When talking with Clydesdale and Shire folks, it's rare for their horses to live a useful life past their teens. I don't know what breeds of horses tend to live the longest . . . but it seems to me that there are an awful lot of old Shetland ponies and Appy geldings around (the Appy mares probably all died earlier due to B*#chiness  )
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Member:
Warwick
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Posted on Friday, Feb 17, 2006 - 12:21 pm:
Thanks for starting this interesting thread, Dr O. The study indicated that the trial population was young horses. Do you know of any studies that address the prevalence of OC in mature horses that were free of OC during their growth years?
This is of particular interest to me as one of my geldings is over 18 hands but was vetted OC-free when he underwent a fluroscopy exam at 4 years of age. He is now 8, schooling 4th Level dressage and (touch wood) shows no indication of joint trouble at this point in time.
Sue
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Member:
Lilly
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Posted on Friday, Feb 17, 2006 - 12:43 pm:
Hi Chris,
If you are in awe of 17 Hand horses, you should meet the big mare at my barn. She is a Hanoverian cross and over 17 Hands. Everything about her is big but she has a wonderful personality. She has been teaching me a lot about individual horse behavior and learning how different horses communicate in their own special way. When I enter her stall she loves to spin around and point her rear end towards me. She then backs towards me quite aggressively but her ears are not back. All she wants is to get her butt scratched. The behavior might scare the crap out of someone who doesn't know her.
Ann
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Moderator:
DrO
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Posted on Saturday, Feb 18, 2006 - 10:26 am:
Sue OC is occasionally diagnosed in older horses but we do not believe the OC developed later, it formed during growing and for some reason or another did not cause problems until later in life.
DrO
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Member:
Warwick
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Posted on Monday, Feb 20, 2006 - 11:50 am:
Many thanks for the update, Dr O. It's comforting to know that my big guy should be in the clear!
Thank you for this wonderful website and all your dedication.
Sue
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