In the same way that the weight bearing ability of a bridge is only
marginally a function of its height off the ground or the weight of the
materials from which it is constructed. How it is engineered and the
quality/composition of the materials used is far more important.
As an example...I can remember a physics assignment in high school where
we were all given 55 tooth picks (all the same brand) and a tube of DUCO
cement and told to build a bridge that spanned 6 inches. After all the
bridges were built, we brought them to class and the teacher spanned them
across the classroom desks, hung a bucket off of them, and proceeded to
add weight to the bucket...until the bridge broke.
The purpose of the assignment was to design and build a bridge that would
support the most weight before breaking. The differences (everybody
using the same materials and spanning the same distance) were substantial
(from ~200 g to ~1.5 kg).
Jesus rode a donkey (ass) into Jerusalem. Presumably it didn't have too
much trouble carrying his weight (donkeys are notoriously good weight
carrieres) which was probably as much as 50% of its body weight. Ponies,
too, are notoriouly good weight carriers.
How a horse is put together, and the composition of the materials (bone,
muscle, fat, ligaments, etc) is a far better indicator of the weight
carrying ability of a horse than is its total body weight. Short
coupling, strong muscles over the loin and along the underline for
supporting the back, strength and resiliancy in the ligaments of the
back, and great flexibility in the sacro iliac joint are a number of
things to look for in a horse that you want to carry weight. In addition
you want to look at the conformation of the legs, the substance and density of
bone, the quality of hoof, the resiliance of the supporting ligaments and
tendons (especially those of the lower leg i.e. the suspensories and the
flexor tendons).
Susan's data about the rider/horse weight ratio at Tevis tells me nothing
more than "the average endurance rider with all his/her tack weighs about
20% as much as the average endurance horse." Which is only slightly more
informative than saying the average person with a bunch of tack weighs
about 20% of the average horse (which is also probably approximately
true). Although, in general, the average endurance rider is probably
lighter than the average person. And the average endurance horse is
probably lighter than the average horse.
It doesn't mean that an endurance horse can't carry a higher percentage
of its body weight...it might just mean that most people aren't that big,
and most horses aren't that small. On average horses weigh about 5x as
much as people do (and I didn't need a study to tell me that).
In short, don't ask the question "What percentage of its body weight can
my horse carry?" The question is almost totally irrelevant. Weight
carrying ability is (I won't say "not at all") is hardly a linear
function of size at all.
Generally speaking, a smaller horse can carry a higher percentage of its
body weight than a larger one (in much the same way that...all other
things being equal...a shorter bridge can suppport more weight than a
longer one), but this is still a gross generality and I would never dream
of trying to put a number on it.
If you want to know if your horse is a weight carrier...look at the way
it is built...don't put it on a scale.
kat
Orange County, Calif.