When I was shopping for an Arabian to be competitive for
50s and eventually 100s, I wanted one that had at least 8" cannon bones -
because I'm a heavyweight and the horse I was getting would be taller (over
15.2) and carrying more weight himself. Some
breed registries with inspections require or recommend their breeding stock to
have a minimum cannon bone measurement. ie. 19
cm (7.5 inches) for Spanish horses and Trakheners. 8" for Canadian sport
horses. 7" for Shagya are a few that I could find.
We have all seen those stocky bulldog QHs with tiny
cannon bones ... not a perfect fit and totally due to selective breeding.
"Foundation" QHs and some paints tend to be bigger boned. Native and wild horses or those breeds that are measured and
inspected tend to have better size cannon bones for their weight than
manufactured/Americanized horses as the only way to keep breeding horses w/ good
bone is to require it by inspections or upholding breeding standards.
Same thing has happened with European dog breeds
introduced to US. Their breed counterparts overseas tend to be sturdier because
of stricter requirements.
So what is the breed standard for Arabians? They
supposedly have more "dense" bone and are typically smaller stature, so
perhaps don't need as much cannon bone circumference under usual
conditions? Of course, keep in mind how much weight is added to the horse
by the rider.
here is an abstract from an article on weight carrying
ability:
To answer the question of whether horse height, cannon bone circumference,
and loin width can be used as indicators of weight-carrying ability in light
horses, eight mature horses underwent a submaximal mounted standard exercise
test under four conditions: carrying 15, 20, 25, or 30% of their body weight.
Heart rate was monitored, plasma lactate concentration was determined in jugular
blood samples pre-exercise, immediately post-exercise, and 10 minutes
post-exercise, with serum creatine kinase activity determined at the same times
as plasma lactate concentrations, with additional samples collected at 24 hours
and 48 hours post-exercise. Muscle soreness and muscle tightness scores were
determined using a subjective scoring system 24 hours before and 24 hours after
exercise. Heart rates remained significantly higher when the horses carried 25
and 30% of their body weight. Plasma lactate concentrations immediately and 10
minutes after exercise differed when horses carried 30% of their body weight
compared with 15, 20, and 25% weight carriage. Horses tended to have a greater
change in muscle soreness and muscle tightness when carrying 25% of their body
weight, and a significant change in soreness and tightness scores was found in
horses carrying 30% of their body weight. Loin width and cannon bone
circumference were found to be negatively correlated to the changes in muscle
soreness and tightness scores. In conclusion, the data suggest that horses with
wider loin and thicker cannon bone circumference became less sore when carrying
heavier weight loads.
