A Note about Sugarbush Draft Horses

I see it over and over again, and no matter how many times it's said, it's still wrong. "Sugarbush Drafts are just an Appaloosa Draft Cross". Uh.... no. The Sugarbush Draft Horse was a breed created many years ago in Ohio. While the initial cross was made using Percherons to Appaloosas, in the many generations following, the breed has been solidified into a consistent type. Saying these horses are "just" a draft cross makes as much sense as saying that AQHA horses are "just" a Thoroughbred cross, American Cream Drafts are "just" a dilute Belgian, or that Morgans are "just" a grade.

Thursday, February 9, 2012

Conformation Clinic: The Forelegs

Yesterday, we discussed the shoulder of a horse.  Today, I want to talk about the horse's front legs, and how to angles of those legs affect a horse's future soundness.  Like the shoulder, there are a lot of imaginary lines involved in measuring this, and those lines can often get overwhelming.  I hope to break them down into something that makes a little bit of sense.

Today's example horse, is Boo, a 13 year old Arabian Gelding.  I've often referred to Boo as my "conformational nightmare" (in a loving way of course) because while he has all the "foof" you can want, his bits and pieces aren't exactly correct.  Before I embarrass the poor guy though, lets talk about the ideal foreleg and it's purpose in the horse.

The Front Leg:
The natural balance of a horse puts about 60% of the animal's body weight on the forelegs.  This means that the front legs are doing most of the work in supporting the entire body of the horse. Good muscling and straightness of bone help to prevent soundness issues.  The size of the tendons as compared to the size of the horse's joints and bones is also important.  They must be large enough to support the weight above, and angled in a manner to be the most efficient.

The pasterns should slope at the same angle as the shoulder.  This allows the joints to have a spring effect with out damaging the internal structures.  When the angles are the same, it minimizes the forces acting upon the connective tissues.  Since none of us wants a physics lesson, you'll have to trust me on this.  The pasterns should fall within a range of 3/4 to 1/2 the length of the cannon bone.  More then 3/4 the length of the cannon is considered long, while less then half is considered short.

Ideally a horse should have a forearm longer then the cannon bone.  This allows the horse more length of stride with less effort, and absorbs some of the concussive forces (from the impact of the leg striking the ground).  A short forearm will give the horse more "action" but can also inhib a horse's speed abilities.

Leg Placement on the Body:
Ok,  so we know what we should be looking for, the big question is, how do we figure it all out.  Many of those phrases are pretty vague and while they seem to make sense, our confusion appears as soon as those dreaded colored lines show up on a horse picture.  Uh oh, I think I can see some now!
Those red lines may look familiar from the discussion on shoulder angles yesterday.  The blue line is measuring Boo's withers to his elbow.  Ideally this line should be straight up and down (vertical) but you can see it's not.  The yellow line is where the vertical should be.  One of the things that becomes aparent from that triangle and vertical line comparison, is that Boo has a shallow chest, hence his legs are not able to be placed in the ideal position.

I chose Boo, because he is a wonderful example of one wrong angle setting the rest out of place.  If you look at the slope of his shoulder, you can see that it is very steep.  This means that Boo should have a jarring gait that tends to be short and choppy.  And yes, you can ask any one who has ridden him, and they will tell you this is a fair assessment of his way of going.  But, that upright shoulder moves his withers forward, puts the point of his chest in (toward his body), which makes that blue line have to slope back to meet his elbow.  In other words, his center of balance on the forehand is not vertical, and thus causes more wear and tear on his legs.
Here is a horse with a much better leg placement.  Keeley is a 22 year old Quarter Horse mare.  You can see here that her withers to elbow line is not quite vertical, but the mare is leaning forward (for the cookie used to get her ears up).  The slight variation shown here is well within what is considered an ideal range, especially considering the mare is not standing perfectly - and really, how often DO they stand perfectly?

You can also see that Keeley has a much better shoulder slope, but a tighter shoulder angle (the longer red line is laid back more, but the joint isn't as wide on the grey horse as the bay).  This indicates that Keeley will have some inhibition in stride length, because of how she's put together (and oddly, she tends to take small steps).

Notice how the yellow line on Keeley (grey mare) falls almost perfectly down the backside of her front legs?  This is the ideal conformation placement of the legs in relation to the rest of the body.  Boo's legs (the bay gelding) peek behind the yellow line, a conformational fault often called "camped under" "standing under itself".

Straightness of Leg:
You can already see from the placement of the leg on the body that Boo's front legs aren't ideal, but lets look into this a bit more.
The red lines again show the points of his wither, point of chest, and elbow (from top down).  The yellow lines are "guide lines" and are perfectly vertical.  The rightmost yellow line is straight down from his elbow, and the leftmost is striaght up from the tip of his hoof.  This is the ideal placement for his leg - no part of his leg should fall outside these yellow lines, but his pastern does.  The pink line in there, is placed at the center of his upper arm bone, and is also vertical.

Now, lets pick apart the poor gelding's legs!  Starting from the top, and working our way down, you can see that the back side of his leg does not line up well with the right most yellow line.  This is because Boo's leg attaches too far forward in relation to his center of balance, and so he must stand "under himself" in order to keep from tipping over.  Intense impact, such as jumping, higher level dressage movements, or riding through difficult terrain would be hard on the soundness of this horse's legs.

Calf Knee:
Next you can see that the front edge of Boo's leg seems to fall further away from the left most yellow line as you move down.his leg almost makes a backwards C shape"
The green line shows the backwards C shape I was referring to above.  This fault is known as calf kneed (although Boo's version is minimal).  It is commonly seen in horses who stand under themselves, but is more of a conformational concern in a horse who has a good base to its leg.  In Boo's case, this is caused by the pressures of gravity pulling against his angled leg support causing slight hyper flexion.  In a horse with a straight base of leg, being calf kneed is a sign of a weak carpus (front "knee") joint.  Horses who have a weak carpus often will show some signs of being unsound very "young" (mid teens) and require light riding and supplements for their comfort.

In all honesty, I can't think of a single horse who is back at the leg, and doesn't show some form of a calf knee.  I'm sure they exist, but these 2 faults often go hand in hand.

Camped Out, or Standing in front of him/herself:
While Boo is a typical example of standing under himself, the reverse is also a flaw.  Horses whose legs attach behind their center of balance must stand with their legs out in front of their body in order to hold the weight.

This flaw is rare enough that the only good example I could find was a diagram (shown at left).

In most cases, horses who have this type of stance are uncomfortable.  Navicular, laminitis (founder) or other hoof related issues can be the cause of it.  In some cases this fault can be corrected with proper hoof care, in others - such as Navicular Disease/Syndrome - the problem is with the connective tissues (tendons, ligaments).  In most cases proper farrier care is extremely important to keep the horse comfortable. Minor examples of being camped out in the front may be sound for light riding, but I highly recommend veterinary advice before making that decision.

As you can see, camped out is a much more serious flaw then camped under.  While a camped under horse must have it's conformation taken into consideration for the work it is asked to do, most camped under horses are sound and make great trail horses, or light competition mounts. So long as the horse's conformational faults are realized, and their job is chosen based on their physical limitations, the unsoundness issues mentioned above can be avoided.

Over At The Knee:
The opposite flaw from Boo's "Calf Knee" is what is called "over at the knee. This is most commonly seen in young horses, as they grow.  Here are a few examples:

The chestnut Appaloosa gelding (top) shows a minor "buck knee" while the mule (bottom) shows a more obvious example of this fault.  The Appaloosa image was kindly submitted by Mary B, and the Mule from Anna L.  Thank you for the examples ladies!

Here's the colored lines to make the flaw more obvious in case you're still trying to see it:
Notice the bend in the front legs?  That is the flaw that "over at the knee" or a "buck knee" (same thing) causes.  This means that the horse's legs are structurally more inclined to fold, rather then support the horse.  Now, these are both babies, and we tend to not worry too much about being over at the knee as a young animal.  This is because every joint bone has a growth plate on it.  The growth plates are sections of bone that have not yet calcified, and leave room for expansion.  The "I hate science' version: this is where the growing happens.  As these bones expand and lengthen, their relation to the ideal angles of the animal will alter as well.  Often times a growth spurt causes all the bits to get out of line with each other, but time corrects it. 
So, while this is something to be aware of, do not judge young animals too harshly for being over at the knee.  Once the horse is mature though, this is a significant conformational flaw.  Animals who are over at the knee when mature tend to experience more stress on all the joints of the leg.  Just like with Boo above, their conformational faults need to be taken into consideration when choosing a job for them.

Above is the Appaloosa gelding shown at 2 years of age.  While you can still see a slight bend in his carpus angle, it is greatly reduced from his younger picture.  Of course, his dark knees help to amplify the appearance of any variation.  By the time this boy is fully grown (around 6 in horses) I would expect any deviation to be so minor as to be within "normal" range.

The Pasterns:
Ok, so the last part of the leg is the pasterns.  So often I have heard people talk about a horse with "long pasterns" or "short pasterns" or "upright" pasterns.  Yet, when I went to double check my own knowledge, there's rarely ever given a base of comparison.  This leaves people trying to guess more often then measure, and results in a lot of confusion.

But there is a basis of comparison.  The horse!

The green line shown here is Boo's cannon bone length, while the pink line shows both the length and slope of his pastern, and another pink line shows the slope of his shoulder.

The horse's pastern should slope at the same angle as the horse's shoulder.  This creates symmetry and efficiency in the horse's shock absorption.  in Boo's case, the angles are pretty close, his shoulder angle is 52 degrees, and his pastern angle is 54 degrees.  The ideal of course is 45 degrees, with up to 50 degrees being acceptable.  Boo, as we've talked about before, is rather steep in his angles. 

This means that when his legs hit the ground, the concussive forces of that impact are sent right up the leg bones, and into the rider.  In other words, his gaits tend to be jarring.  This is similar in physics to a tight spring as compared to a loose one.  The more area available to flex, the more energy goes into flexing those areas, and not flexing the rider's hiney.

A more laid back angle allows this.  Just think about those lines as pieces of wood, joined with a single nail through them.  Push straight down, and it's likely that the nail will not hold the wood in place, and the angle will ultimately bend into an L shape.  The more upright the pink lines, the more you have to push to get the L.  That force - used to flex the joint - is the energy of impact that is absorbed by proper joint angles.

Upright pasterns (straighter then 50 degrees) make the horse prone to health issues such as Navicular, ringbone, arthritis, and splints.  Overly long pasterns are directly correlated with bowed tendons and leg fractures.  Of course, these are the extremes of problems, but horses with these conformational flaws are more likely to experience them then a horse in the ideal range.

Now, not only is the angle important, but we also have to look at the length of the pastern. Using a measuring stick against Boo's picture, his canon bone measures out to 2.3cm.  His pastern is 1.2cm.  The ideal length for his pastern is based upon the length of his cannon.  At 2.3cm, his pastern should be between 1.15 and 1.725cm.  At 1.2cm, it falls on the shorter side of ideal.

Long pasterns increase the leverage action on the tendons and ligaments of the pastern joint.  This stretches them out, and can cause tears, bows, and other soft tissue injuries easier.  Think of a pry bar.  We all know that a longer pry bar means more force on what ever it is we're trying to pry up.  Well, in the horse, his pastern is that prybar, and the thing being "pried" upon is his own joint.

Too short of a pastern reduces the buffer for impacts though.  Instead of prying at the pastern, we're smashing on it each time the horse's foot hits the ground.  With an average weight of 1000 pounds, that's a whole lot of force to be exerted on such a small area.  The flexibility of a medium length pastern absorbs that, and dissipates it.

The Overview:
We want our horses to have good sound legs.  This means straight support under the horse, and angles that are moderate.  Too much is just as bad as too little in the legs, and with the amount of use a horse gets out of its legs, I personally consider this to be the most important piece of conformation in any horse.

I did not go into size of the bone here, as I will cover that when I get to overall balance.

The Sugarbush Draft Horse:
Now, lets see how all of this works when "super sized".  Today's examples have all been "light" horses (common saddle horse size).  With drafts, the front leg conformation really isn't any different, just larger.

The Sugarbush Draft should have a straight leg, set well under the body.  The joints should be large and "dry" (without excess fat or tissue) and the lower leg should be strong and dry.  The pasterns should be of medium length, and well sloped, with solid well formed hooves to support the horse's weight.

In other words, a good front leg is pretty much universal across all breeds and types of horses.

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