I am starting with a very brief synopsis of Goubaux and Barrier’s principles of ‘zootechnics’ to make sure my readers have context. You can find a longer intro by clicking here.
Even though The Exterior of the Horse was published in 1891, it still offers a very different approach from either veterinary pathologists who look for what is wrong after an issue arises or breeders and trainers of the competitive horse industry, who produce horses that sell young rather than horses that stay sound over the long term. Zootechnics is defined through the reciprocal fitness of the all parts of a horse for the work that they are required to do.
In order to define an absolute equine beauty, zootechnics first asks what do specific parts of the horse actually do. In order to define a relative equine beauty, zootechnics then asks how specific proportions and relationships of those parts of the horse affect their ability to perform the work we humans ask of them. In order to answer those questions, Goubaux and Barrier divided the horse into three functional regions, the head and neck, the body, and the limbs.
Goubaux and Barrier define the horse’s limbs as ‘broken columns articulated from space to space, (that) support the body and, by their movements, transport the whole from place to place. The limbs may be further defined by their position, form and function into pairs of fore and hind limbs.
- The bones of the forelimbs consist of the shoulder blade, the humerus, the forearm, the knee, the cannon bones and the bones of the pastern, fetlock and hoof.
- The function of the forelimbs is ‘to resist the forces of gravity’ by elevating the horse’s mass while moving forward and they carry roughly 60% of the weight in all quadrupeds including the horse
Zootechnic equine beauty is dynamic. Some beauties are absolutes, required for all horses to be healthy and sound. Other beauties are considered relative, varying depending on what sort of specialized work is demanded of a horse. That means that the beauties of the equine forehand vary according to their fitness for the work that the horse is required to do.
The amplitude of the horse stride is limited by the degree of rotation allowed by the shoulder blade. When the foreleg is reaching forward, protraction, the rotation of the shoulder blade allows it to be brought upward and backward to a horizontal position. When the forehand is retracting, the downward and forward rotation of shoulder blade is limited to its reaching the vertical where it can best support the horse’s mass. Forcing the shoulder beyond that point causes injury.
Perhaps because the horse’s forelimbs are connected to their trunk by the shoulder girdle, a sling of thick fibrous connective tissue and muscle, instead of a collarbone, Goubaux and Barrier found it difficult to define absolute beauties of the forehand. Goubaux and Barrier considered a long shoulder blade an absolute beauty because length increases both muscular leverage and amplitude of stride, regardless of its slope.
We have a learned a lot about the importance of the shoulder girdle since The Exterior of the Horse was published. For one, we now know that the entire shoulder blade rotates around the attachment of the serratus ventrales that attaches about midway on the inside of the shoulder blade.
- The serratus ventralis thoracis attaches to the ribs and rotates the shoulder blade towards a more vertical position during retraction of the foreleg.
- The serratus ventralis cervicis attaches to the first few cervical vertebrae and rotates the shoulder blade towards a more horizontal position during protraction of the foreleg.
Although the biomechanics of the forehand tend to reflect those of their hindquarters, discerning a horse’s individual abilities through the relative beauties of the shoulder blade requires developing your ability to perceive these factors that strongly influence the relative beauties of the shoulder:
- The length of the shoulder blade, from the point of the shoulder, indicating the shoulder joint, to the top of the blade near the withers
- The slope of the shoulder blade, indicated by the line of scapular spine
- The length of the humerus, from the point of the shoulder to the elbow
- The slope of the humerus, from the point of the shoulder to the elbow
- The position of the shoulder joint at the base of the neck
- The position of the elbow joint
One of the primary functions of the vertebrae is to protect the spinal cord and the associated nerves from compression and damage. This protection is even more essential at the junction of the cervical and thoracic vertebrae as they are required to protect the thoracic enlargement of the spinal cord. This enlargement is complex enough to be considered a small brain in its own right. It directly controls the activities of the fore legs, so the nervous impulses do not have to travel all the way to the horse’s head and back.
That means that the vertebrae of the thoracic spine themselves have the least allowance for movement of the horse’s entire ribcage. The muscles that attach to their vertical vertebral process help to stabilize the shoulder and foreleg, so those bony levers develop differently depending on the relative beauties of the horse’s shoulder and the work they are asked to perform. The profile of the withers varies depending on the height of those processes.
- The top line of the withers is a relative beauty because the bony vertical processes of the thoracic vertebra that define the topline of the horse’s back are biomechanical levers that develop differently depending how the horse functions biomechanically.
- Although the distance between the top of the withers and the elbow joint may be the same, the length of the shoulder blade is a relative beauty will vary drastically depending on its slope.
- The angle and position of the shoulder joint is a relative beauty that varies according to the relationship between the shoulder blade and the humerus.
- Like the femur, the length and slope of humerus is a relative beauty that depends on the type of work a horse is intended to perform.
- The apparent length and depth of the base of the neck are relative beauties that depend, not only the development of the muscles attached to the shoulder and humerus, but on their slope and the position and angle of the shoulder joint.
- The position of the elbow joint is a relative beauty that depends on the angular displacement of the humerus. It should be energetically efficient AND its placement should passively help to support the horse’s mass
- The width of the breast and the prominence of the sternum are relative beauties. Their characteristics can be increased through muscle development but their essentials vary as the position of the shoulder blade, humerus and the shoulder and elbow joints along the rib cage vary, according to the relative lengths and slopes of both bones.
The relative beauties of the shoulder vary according to so many different factors that it can be difficult to interpret what you see. Imagining the position of the shoulder blade and humerus as hands on an analog clock face may be dated, but it is a very useful image. Make the long or minute hand represent the shoulder blade and the short or hour hand of the clock represent the humerus. Since the hands are moving clockwise, the horse is facing left.
- The slope of the shoulder blade may vary between a more vertical 70o or 1o’clock and a more sloping (45o) or 2 o’clock
- 3 o’clock is the shoulder blade’s horizontal limit of forward extension
- 12 o’clock is the shoulder blade’s vertical limit of rearward flexion.
- The standing position of the humerus when the horse is at rest may vary between a more vertical 5 o’clock and a more horizontal 4 o’clock
I have also found the way types of horses were defined by use in old cavalry manuals and Baroque texts helpful. When horses were essential, the relative beauties of the shoulders of sound serviceable horses who stood up to the work demanded of them tended to vary in these patterns. From left to right, are the Square Horse selected for endurance and agility, the Rectangular Galloper selected for speed on the flat and the Trotter selected for work in harness:
In these stick figures, the shoulder blade is red and the humerus is blue. I have done my very best to limit the number of variables, so to the best of Microsoft’s ability, the length of lines of the same color are the same in each figure. The distance from the top to the bottom of all three figures is the same.
The single change I had to make was to lengthen the green line of the forearm in the Square Horse in order for the cannon and pastern to be correctly positioned. The pronounced slope of the shoulder blade and humerus elevate the shoulder and elbow joints relative to the hip joint even when the horse is standing at rest.
While we are told that the ideal slope for the pastern and hoof is always 45o, the angle of the hoof and pastern is actually a relative beauty that should reflect the slope of the shoulder if the horse is to remain sound. So the short yellow line at the base of the limb reflects that zootechnic dynamic.
Those who have questions about how the information in these posts can be pragmatically applied to schooling their horses can find detailed descriptions and instructions in my horse training series, Light in the Saddle. Those want to discuss the implication of these posts on work under saddle are welcome to join my Facebook group aimed at trainers and serious riders, The Isometric Rider.