Re[2]: cannon bone size

[Jack_Weaver@cc.chiron.com]

In my first post I state I'm trying to evaluate an endurance prospect 
(nearly 7 yr old gelding Arab).  He has "medium" legs.  I'm looking for 
(cheap) ways to evaluate soundness and potential.

Susan Garlinghouse replied:

> However, the short answer is that we couldn't find a statistical 
> difference in cannon circumference between completions and pulls, but the 
> average measurement for all entries was about 7 1/2" measured midway 
> between knee and fetlock.  Because Tevis entries are not a random         
> population, we drew the conclusions that 7 1/2" is a good measurement to 
> shoot for in an average sized (950 pound) horse and the more the
> better.  We also concluded that many horses with inadequate bone went 
> lame prior to entering Tevis and so weren't there to be measured in the 
> first place.

> We attempted to prove a hypothesis that would have nailed down better 
> predictions based on CBC, but the hypothesis didn't prove out---which 
> in itself indicated that CBC is only one of MANY factors to consider 
> when looking at a prospect.  Of course, look at angles, joints and all 
> that.

I was also informed by Lynette that the weight of the horse can also be 
considered.   I think this was also Susan's  formula.

> If you add up the total mass of the horse's body weight plus the 
> weight of the rider and tack, and divide that number by the cannon 
> bone circumference, and then divide that number by two; the resulting 
> number should not exceed 80 lbs per inch of cannon bone 
> circumference, and ideally should be 75 or less.  Horses that have to 
> carry more than 80 pounds of weight per inch of cannon bone had a 
> higher incidence of lameness.

I presume an overall average for an endurance type Arab would be around 
a 7.5" circumference since body weight would not be that different, but 
the weight formula would be a little more accurate.

Ok, there are other factors.  I would think that cannon bone length 
would also be a factor because of leverage (torque).  Two horses of 
equal height can have cannon bones of different length.  I think I would 
prefer the horse with longer upper leg (a larger bone) and shorter 
cannon bones.  Has there been a study of cannon bone length?

And as I was reminded by Sandy:

> While circumference is not a small matter, bone density and shape are 
> equally if not more important. Many a top notch distance horse had 
> seemingly smallish bone, but high quality bone, with good shape and 
> excellent density. Good luck! sandy

I agree, but bone density (quality) is much harder to measure.  I think 
ultrasound is good for this, but costly.  Are X-rays any good for 
assessment of bone density?  I have 3 month old X-rays of this horse.


So now I've decided!  I will take the ratio of upper leg length to 
cannon bone length multiplied by cannon bone circumference and divide 
that by the number leg X-rays I have and this should be less than his 
age in months.  Then I'll say screw it, I'll buy him anyway because he's 
pretty and has a good mind.

Thanks for you help.

Jack

Jack_Weaver@cc.chiron.com wrote:
> 
>      I think I remember a study of cannon bone length and diameter in
>      endurance (Tevis?) horses.  Can anyone tell me where I can find it?  I 
>      looked around the Tevis home page and some in the ridecamp archives
>      without success.  I'm looking at a new prospect with what I would call 
>      medium size legs and would like to see how he compares to some
>      successful endurance horses.
> 
>      Thanks for any help
> 
>      Jack