The Body Length Line. This line is going to be pretty critical to the rest of your critique. You will join the dot at the point of shoulder to the one at the point of buttock with a line - most horses this will be a slightly downhill sloped line. Step 4
Join the dot at the top of wither to that at the point of shoulder. Then join the point of shoulder to the point of elbow with another line.
Now, measure the first line - it should run along the scapula of the horse (the shoulder bone).
What did you get? :
Divide that by the body length - and turn it into a percentage. :
We now have the shoulder length, the ideal shoulder is no less than 1/3 of the body length.
Measure the second line.:
This is the humorous length. We're going to divide that by the shoulder length... and turn it into a percentage :
The ideal humorous is at least 50% of the shoulder length, longer is better.
Now, Shoulder slopes and angles.
The shoulder slope is found by measureing the angle between the scapula and a horizonal line (don't use the body length line, because it's usually slightly sloped, but a straight line running horizontally from the point of shoulder across the photo.) The "ideal" is between 45 and 50 degrees, though some sources will say between 40 and 55.
The shoulder angle is found by measureing the angle between the scapula line and the humorous line. The "ideal" is 100 degrees.
What do the angles mean? They will tell us if the horse is going to be more prone to having short choppy strides, how high it'll be able to lift it's knees... the scope and flexibility of the horse's front end.
They don't stand alone though - a horse is the sum of all it's parts, so we're going to connect the angles with the lengths. The longer a scapula and humorous the more compensation there is for less than ideal angles.
What can you tell me about your horse's shoulder?