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Riding Drafts
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neal
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 Posted: Tue Nov 4th, 2008 04:16 am
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hey  dr, deb , got a chuckle out of this cat fight between you an pam . shes probl;y  hopes to get something going with the martingale man . lol. we all know a good  horseman  has no need of a martintale. apprently shes not intersted in good horsemanship. now about riding drafts in my assocation with hundreds of saddle type horses i cannot recall see  bone deformities  among them , if so it was rare, such is not the case with draft stock,  it was not        uncommon to see deformites ring bone an splints . the bone in draft horses is course, where as in the arabian his bone is dence  thefor stronger, all light horse breeds stem from the arab so they all carry dencer bone to some degree. when i was a kid we had a team of percheons this one was tall rangey  type 16, h or better           i used to ride him bareback an he could streach out an lope pretty good , percheons have arab blood in them i believe. just  my 2 cents .  neal

DrDeb
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 Posted: Tue Nov 4th, 2008 05:19 am
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Hey, Neal -- I think you probably don't mean anything bad by it, but I'd appreciate not being referred to as a "cat". I am the teacher here, and I am requesting that your language reflects the appropriate level of respect. Sometimes, Neal, I get students who are immature and/or difficult such as Pam. It's my job to wrestle with them, and by God, you ought to know if you've read very much here at all, that I am not one to mince words. I am willing to go to the mat with any student that I think has potential, even if they act, at the time, like tantrummy toddlers. But there are no "cat fights" here. You go to the bar, OK Neal, if you want to see a cat fight, but you will never find me in a bar.

As to the statement you make about "all light breeds of horse coming from the Arab," that is a false idea. Some light breeds have Arab in them, but by no means all. Mustangs, for example, have zero Arab blood, nor has any other Iberian breed (Andalusian, Lusitano, Sorraia, etc.). There are also many Asian riding breeds that have no Arab blood: Marwari, Plateau Persian, Lokai, Bashkir, Akhal-Teke, etc. Your confusion may come from the fact that you think the Arabian is an old breed, but in fact the Arabian originates in Syria and southern Turkey no earlier than the time of Mohammed, i.e. in the 8th century -- and in actual fact that's probably about two centuries too early. The Arabian comes FROM some other middle-eastern breeds, it is not the ancestor OF them.

Another false idea that you have is that the Arabian (or other light breeds) have "denser bone". I got so sick of hearing this idea when I used to give a lot of seminars to Arabian breeders back in the 1980's, that I finally did a formal study on it, using the large collection of domestic horses housed at the U.S. National Museum of Natural History/Smithsonian Institution, where I used to work. What I found was:

(1) Arabians, and other light breeds, have normal bone density. High bone density is a disease called pachyostosis, and this disease is extremely rare in horses.

(2) Heavy breeds (and any heavy individual), if they weigh over 1450 lbs., bone density tends to drop off. The heavier the individual, the more it tended to drop off, so that many of the heaviest draft horses in the collection had bone verging on osteoporotic, i.e. very low bone density or abnormally low bone density. The best predictor of low bone density is large size/massiveness.

Heavy horses are more prone to ringbone and sidebone, which are abnormalities that are promoted by concussion, simply because they are massive. The maximum weight for any wild horse or horselike animal in nature is 1100 lbs. Between 1100 lbs. and 1450 lbs. lies a kind of "gray area" where you could have the horse that big and still be OK. Above 1450 lbs., your chances of having the horse be sound get less and less.

Another result of my study was that the larger your horse, the smaller the bone-tendon circumference will be relative to his weight. The average circumference-to-weight ratio in domestic horses (excluding miniature ponies) is 8 inches per 1,000 lbs. of weight. Once we get over about 1450 lbs. we never find horses that will meet this rule -- it would require that a 2,000 lb. big draft horse have 16" of bone, and I can tell you Neal, there is not one single record of any horse with legs that heavy. The average for horses that weigh between 1500 and 2,000 lbs. is 5" per 1,000 lbs. of mass. This is another reason that big horses suffer far more frequently from all kinds of unsoundnesses from the hock and knee down.

What about horses that weigh less than 1100 lbs.? Those horses tend to have at least 8" of bone per 1,000 lbs. of mass, and as you get down toward the smaller end, i.e. animals that weigh 600 to 800 lbs., they may have as much "bone" substance as the Mongolian Wild Horse, which is 14" of bone per 1,000 lbs. of weight.

You are right about one thing, though, Neal: Percherons do indeed have Arab in them. This was done in the 18th century as an attempt to make them more compact, more active, and improve the quality of the horn of the hoof. -- Dr. Deb

neal
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 Posted: Tue Nov 4th, 2008 06:55 pm
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hi dr deb please  accept my aplogy . i in no way refered to you as a cat . i didnt mean it that way .as to this bone stuff thanks for clarifiying it for me those are ideas iv, heard for long  time .  neal

Pam
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 Posted: Sat Nov 22nd, 2008 01:15 am
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Neal,

A couple of things to straighten you out:

1)  I am not interested in getting anything going with the martingale man

2)  I am interested in good horsemanship - practice what I know everyday with my  horse - will continue to the learn the skills needed be-it here or elsewhere

3)  I did not know martingales are harmful to horses at the time - that's why I asked about them - would never allow my horse to be ridden in one now!  I am a fan of Philippe Karl and his way of contact with the bit.

4)  Did not ride in the clinic with the martingale man and stated I wasn't going to after I was educated about them.

Regards,

Pam

neal
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 Posted: Sat Nov 22nd, 2008 08:22 pm
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hi pam i thought i replyed to your post, but i dont see it any more on the board.i want to thank you for your reply, hope you continue to post, im glad your pursing good horsemanship, best wishes neal

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 Posted: Mon Dec 1st, 2008 08:59 pm
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"The average circumference-to-weight ratio in domestic horses (excluding miniature ponies) is 8 inches per 1,000 lbs. of weight. Once we get over about 1450 lbs. we never find horses that will meet this rule -- it would require that a 2,000 lb. big draft horse have 16" of bone, and I can tell you Neal, there is not one single record of any horse with legs that heavy. The average for horses that weigh between 1500 and 2,000 lbs. is 5" per 1,000 lbs. of mass. This is another reason that big horses suffer far more frequently from all kinds of unsoundnesses from the hock and knee down."

I am responding to the logical sounding statement above. I asked an engineer about weight bearing capacities of cylinders (which are a rough approximation of the idea of "bone"). My question is: Are there draft horses out there will 11 - 12 inches of bone? In which case they should be quite capable of carrying their weight and that of a rider.

This is his response: Load depends on the area. A cylinder with twice the circumference has more than twice the area. You would need a cylinder (of similar material) with a
circumference if 11.31 inches to support 2000lbs

DrDeb
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 Posted: Mon Dec 1st, 2008 11:55 pm
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Sunny, the weight-bearing capacity IN POUNDS of a cylinder is a function of:

(1) The cross-sectional area (or the circumference; one is directly convertible into the other) of the cylinder. In other words, "how thick the post is".

(2) The material out of which the cylinder is made (if you have two cylinders of the same cross-sectional area, one made of steel and the other made of styrofoam, the steel one will bear more weight). What we are talking about here is what is called the 'failure point' of bone in resisting compressive forces. This will fall somewhere between styrofoam and steel; but closer to styrofoam. Bone's failure point is actually less than that of wood. So your statement about 'a cylinder of 11-12 inches in circumference should bear the weight perfectly well' is incorrect because you have not thought about the difference between bone and steel.

(3) It also matters what you mean by 'it will bear weight perfectly well'. What does 'perfectly well' mean? Well, it would mean at least these two things: one, that the legs won't crush, fracture, or collapse when the horse + rider is standing still. Much more importantly, it will have to mean that the legs will stand up to the ADDITIONAL STRESSES that are normal and unavoidable parts of MOTION: torque, peak impact forces, centrifugal and centripetal forces associated with accelleration and deceleration. In other words, Sunny, we never want to design a bridge, for example, that is expected to undergo vibration, wind-shear, bounce, and other forces of movement by building it only to the level of specification required merely for it to support its own weight. Typically, engineers allow a margin of at least 50% "over". This is true not only in engineering bridges, windmills, car engines, and other things that move, but even in the design of houses and farm buildings: you have to allow for wind-shear and snow load. So again, your statement is incorrect because you haven't remembered to include these factors, which in the living horse are crucial to ongoing soundness and even to the animal's survival.

(4) We know that "11-12 inches" is not enough also by the best test in the world: looking at nature. The 'natural' equines -- and to be fair, selecting only those that are relatively heavy-bodied, as the domestic horse is -- have bone-to-mass ratios in the 14-inch range, in other words, approximately twice as much "bone" as the average figure for domestic horses. We can check this idea by referring to other hoofed domestic mammals such as cattle and goats: their wild relatives, too, have "bone" approximately twice as substantial as the domesticated varieties.

(5) Another check on the reasonableness of what I have told Neal -- because, for goodness sake, it isn't just 'logical-sounding' -- is to remember the fact that in nature, no equine ever exceeded 15 hands in height or 1100 lbs. in weight. Draft breeds begin getting really large only after about 1820, and the increase in size from Suffolk-Punch sized farm horses, that weigh 1100 to 1400 lbs., to the Belgians, Percherons, Vladimirs, Shires, and other behemoths now bred, is correlated historically with the coming of railroad systems which made it profitable for teamsters to make a circuit, picking up big loads of farm produce, which they then drove to the railheads. Fashion and marketing savvy played their part here too, as breweries and other companies realized that really big horses impressed people (huge horses are expensive to feed: so the thought back in those days, when the ordinary farmer could not afford any such kind of horse, was 'blimey those Guinness people must be doing really well').

(6) No equine whatsoever, not even 'Big Jim' or the other largest draft horses we have on record, has ever had 16-inch cannon bones, or even 15-inch cannon bones. The most substantial cannon bone measurement of which I am aware is less than 15 inches, whereas the top reported weights for the largest draft horses are in excess of 2,000 lbs., on up to 2200 lbs. Looking at this, and looking at all the reported tables of data for large horses, it may be seen that the average for horses weighing over 1500 lbs. is 5 inches of bone per 1,000 lbs. of mass, which is more than 2 inches less than the AVERAGE for domestic horses across the board, and more than 9 inches less than what the Plains Bontequagga or the Przewalski horse (see photo attached).

(7) I am not trying to use this information to discourage anyone from breeding draft horses. What I am doing is giving you the FACTS, and then asking you and other people to use common sense in asking big, heavy horses to perform -- especially when you ask them for work which involves bounding (jumping and landing) and/or highly suspended gaits (i.e. passage, a lot of trotting, etc. as in the dressage style of competition). The intended use of the draft TYPE is to work at a WALK and/or at the draft horse's version of a "stepping trot", a type of semi-suspended or nonsuspended trot. If you don't know what a "stepping trot" is, go get a copy of Eadweard Muybridge's "Animals in Motion" and look at the sequence photos of heavy draft horses trotting -- you will see that although their legs are moving in diagonal pairs, they don't typically bound up into the air like a smaller horse that is of riding TYPE will.

(8) I suggest that you telephone Equus Magazine (at (301) 977-3900, push "0" when the recording comes on, then ask the secretary if you can talk to Christel). Obtain from them the back issue containing the article "Size Matters", and read it. There you will find this information backed up by other experts -- veterinarians who attend the massive horses so fashionable at present in competitive dressage. These experts are asking you to do the same thing that I am asking: use common sense; and never select a horse for purchase merely because it is big. -- Dr. Deb

Attachment: Przewalski mare Monarto cprsd.jpg (Downloaded 259 times)

sunnyriot
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 Posted: Tue Dec 2nd, 2008 03:55 pm
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I am still a bit confused.

Sunny, the weight-bearing capacity IN POUNDS of a cylinder is a function of:
(1) The cross-sectional area (or the circumference; one is directly convertible into the other) of the cylinder. In other words, "how thick the post is".
>>not on a one to one basis however as shown by the engineer's calculation<<

(2) The material out of which the cylinder is made (if you have two cylinders of the same cross-sectional area, one made of steel and the other made of styrofoam, the steel one will bear more weight). What we are talking about here is what is called the 'failure point' of bone in resisting compressive forces. This will fall somewhere between styrofoam and steel; but closer to styrofoam. Bone's failure point is actually less than that of wood. So your statement about 'a cylinder of 11-12 inches in circumference should bear the weight perfectly well' is incorrect because you have not thought about the difference between bone and steel.
>> I don't understand this point. I assume that both the 8" boned horse and the horse with 11.3" of bone have "bone" made of the same material i.e. bone and tendon.<<

(3) It also matters what you mean by 'it will bear weight perfectly well'. What does 'perfectly well' mean? Well, it would mean at least these two things: one, that the legs won't crush, fracture, or collapse when the horse + rider is standing still. Much more importantly, it will have to mean that the legs will stand up to the ADDITIONAL STRESSES that are normal and unavoidable parts of MOTION: torque, peak impact forces, centrifugal and centripetal forces associated with accelleration and deceleration.
>> Ok, this I get. Of course, bigger bone would mean increased limb weight, so increased torque on a moving limb, so this would affect the joint (not the weigh-bearing ability tho). Increased weight/torque is also added by shoes and boots. I imagine owners with horses light in bone should avoid these?
I will ask my engineer friend about the forces on the same cylinders from a moving object. <<

(4) We know that "11-12 inches" is not enough also by the best test in the world: looking at nature. The 'natural' equines -- and to be fair, selecting only those that are relatively heavy-bodied, as the domestic horse is -- have bone-to-mass ratios in the 14-inch range, in other words, approximately twice as much "bone" as the average figure for domestic horses. We can check this idea by referring to other hoofed domestic mammals such as cattle and goats: their wild relatives, too, have "bone" approximately twice as substantial as the domesticated varieties.
>>If we have domestic horses of 7" or 8" of bone that are surviving into old age soundly is that "not enough" for our purposes? Sure more would seem to be better, but again, limb weight will add torque etc, so perhaps, bone size in the domestic horse represents a trade-off between limb weight-bearing capacity and minimizing joint stress? Could this be an equally important factor in a performance horse?<<

Thanks for clarifying these concepts. I have no desire to purchase a "large" horse, draft or otherwise, as I am a small person and the kind of riding I do suits a more agile animal. I personally have not seen as much lameness in heavier horses as in light horses, but have not allowed for differences in use certainly.

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 Posted: Tue Dec 2nd, 2008 05:21 pm
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I'm not sure this has helped at all LOL! Comments from the engineer:
Of course, larger, heaver more heavily muscled animals will produce more
force, and the bones will be bigger. But again, the same laws of force /
area still apply.

The simple fact that doubling the diameter of a support, produces 4 times
the area and that 4 times the area will support 4 times the load is really a
very simple thing. This fact still applies to dynamic situations.

But, of course, there are many factors that affect the whole thing.

This does not even take into account that bones can acquire more or less
size depending on use over time. For example, the bones on a baseball
pitcher's throwing arm are much thicker and more dense than in the other
arm. This also applies to sprinters....and weight lifters and everything
else...

Tom

DrDeb
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 Posted: Tue Dec 2nd, 2008 07:42 pm
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Tom....your failure to understand the points I have made is due to your own inability to correctly comprehend physics concepts. Your objections are fallacious because you are muddled.

Your inability to understand, is however, also due to my inability to do any more to explain it to you here. The way to fix this is for you to attend one of my anatomy/biomechanics classes, in which these basic concepts are always taught. There I would be able to give you the one-on-one attention that enlightening you will require. What I would envision would be repeating the correct ideas to you many times, in different ways, until you understood.

It might also help you to do some background reading. Particularly, I would recommend that you obtain a copy of Schmidt-Nielsen's book entitled "Scaling". The book is quite an enjoyable read. -- Dr. Deb

Tutora
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 Posted: Tue Dec 2nd, 2008 11:27 pm
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OK--I thought it over more and I was thinking of something else with what I said about the increase in area of a long  egg shape. Sorry.

Where was I when Dr. Deb  recommended the lost art of being silent?

I would like to add that  the only horse I've had any hoof bruise issues with in about 23 years of smallish barefoot horses and ponies, is my Andalusian/Percheron gelding Aquila. He's about 16 hh and 1200 lbs., with feet that look great. ( I use a very good farrier, but I've been to a Gene Ovnicek seminar and I'm decently well informed on feet.) He had  a hoof bruise in front as well as in a hind foot this year. It's pretty hard  not to think his size is a factor in that

"And now for something completely different..."---I'm going to be quiet. :-)


Last edited on Wed Dec 3rd, 2008 12:22 am by Tutora

rifruffian
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 Posted: Wed Dec 3rd, 2008 04:28 pm
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Why should size of horse be directly proportional  to likelihood of sustaining bruised feet?

Ben Tyndall
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 Posted: Wed Dec 3rd, 2008 05:28 pm
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I certainly have some muddiness on this topic of bone size vs horse weight. I have not read the Equus article mentioned by Dr Deb. My question for Tom's engineer friend: Regarding the statement "Load depends on the area", is the relation between cross section area and load bearing capacity linear?

My guess is that for substances like steel and concrete cylinders, the answer would be yes, but for the bones in question perhaps not, given that we're talking about a combination of bone, tendon, skin, hair, blood vessels and maybe other stuff (marrow?).

I think the relationship between circumference (which is what we typically measure on the horse) and cross section area (which tells us about load bearing capacity), to which Tom alluded earlier, has to be somewhat significant in this. If circumference is increased by x, the area will increase by x-squared, so the relationship is not even close to linear.

...Ben

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 Posted: Wed Dec 3rd, 2008 08:21 pm
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Hi folks,

Maybe I can be of assistance (mech eng by training, though I haven't done much of it in the last few years).

You're probably best to look at buckling, since we're dealing with thin columns for the most part. See: http://en.wikipedia.org/wiki/Buckling

From:
http://www.springerlink.com/content/v674tvt57gr4t62l/
and:
http://en.wikipedia.org/wiki/Young%27s_modulus
...we note that we're probably dealing with a substance that falls somewhere between wood and concrete in most mat'l properties. If you read the wikipedia entry for where thin beam buckling applies, we're probably not far off in assuming that this is valid.

For simple buckling, force at failure is proportional to moment of inertia. A nice simple calculator here:
http://www.engineersedge.com/calculators/section_square_case_12.htm

Can be used to get that for various thicknesses.

For that 2000lb draft horse mentioned, Dr. Deb's findings indicate that draft horse likely has about a 10" cannon dia. Let's assume for argument that's all bone, and has a wall thickeness of 0.25" (inner dia of 9.5"). That gives I=90.9 according to our calculator.

The guideline says we should be up at 16" dia, however, so let's scale up to the same proportional wall thickness and use a 15.2" ID. That gives I=595, or about 6x the buckling resistance. Makes you think.

I found it amazing that my new Icelandic @~1000lbs and 14hh has a dia measurement of 9", where my old 17hh Holsteiner was 1400lbs and only 10.5" dia. Reading that Wiki entry also reminded me that the shorter leg length factors in favorably as well, since short columns are less likely to buckle (ie 16 hh and 1000lbs isn't the same situation as 14hh and 1000lbs).

For the really dedicated:
http://jeb.biologists.org/cgi/reprint/202/18/2495.pdf

Hope that helps in some way. I don't know if buckling is the best way to look at things, since joints will likely fail before the "beams"/bones themselves buckle, but it's an interesting excercise.

Cheers,
Adam

Last edited on Wed Dec 3rd, 2008 08:35 pm by AdamTill

AdamTill
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 Posted: Wed Dec 3rd, 2008 08:27 pm
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Ben Tyndall wrote: I certainly have some muddiness on this topic of bone size vs horse weight. I have not read the Equus article mentioned by Dr Deb. My question for Tom's engineer friend: Regarding the statement "Load depends on the area", is the relation between cross section area and load bearing capacity linear?

My guess is that for substances like steel and concrete cylinders, the answer would be yes, but for the bones in question perhaps not, given that we're talking about a combination of bone, tendon, skin, hair, blood vessels and maybe other stuff (marrow?).

I think the relationship between circumference (which is what we typically measure on the horse) and cross section area (which tells us about load bearing capacity), to which Tom alluded earlier, has to be somewhat significant in this. If circumference is increased by x, the area will increase by x-squared, so the relationship is not even close to linear.

...Ben

Ben, I'm not the engineering mentioned, but no the relationship isn't linear. Go to the calculator I mentioned above:
OD (outer dia)  ID    I        area (units^2)
16                  15.9  79.5   2.5
16                  12     2195  87
16                  8       3010  150
16                  4       3198  188

This is proving the concept that, assuming it doesn't get so thin-walled as to buckle, a tube on average is much stronger in bending then a rod OF EQUAL MASS. Remember that mass increases dramatically with wall thickness, but bending strength doesn't match that increase. With increases in mass come increased forces as well, questioning again the claim that "bone density" is somehow a benefit.

Last edited on Wed Dec 3rd, 2008 08:30 pm by AdamTill


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