When referring to the study of external horse characteristics, it is zoometrics within zootechnology that is in charge of the complete or partial (regional) measurement of the animal, which must be used to establish certain indexes.
To obtain the lineal measures (height, width, and length), ametric tape and zoometric cane are the standard measuring.
A metric tape presents on one hand, the decimal metric system and, on the other, that if the Castilian bar, divided into “cuartas” (meaning fourths) and “dedos” (meaning fingers). A “cuarta” is equal to 21 cm (9.5 inches) while a “dedo” measures 17 mm (0.5 ich). This type of tape has a mark at 7 “cuartas”, which coincides with 1.47 m (just under 14.2 hh), and which was the minimum height required in the acquisition of three year-old colts fir the Military cavalry. This is the reason behind such sayings as “this colt has to grow a couple of fingers” or “this horse is eight fingers at the withers”.
The cane consists of a rod, marked in centimeters with some bars attached to it, so that a 90 degree angle can be formed, thus facilitating the measurement on uneven ground. In the world of horses, it is a cane that is used for lineal measurements while the metric tape is used to find out the perimeter of the thorax, the knee and the cannon bone.
PRE horses could be subjected to an evaluation of its zoometric measurements on at least two occasions:
- The first, when it is presented at the test for Basic Breeding Stock, to be registered in the Purebred Spanish Stud Book as breeding stock;
- The second is when, at the request of the breeder, the horse is presented at a Tribunal for Qaulified Breeding Stock to surpass a further hurdle within the Selection Scheme and can, therefore, continue to be awarded the distinguishing characteristic of Qualified Breeding Stock.
Height at the Withers
The height at the withers represents the height of the animal and corresponds to the distance that exists between the highest part at the withers and the floor. This highest part of the withers is easily felt because anatomically, it consists of the spinous processes of the first thoracic vertebrae.
Previously, a metric tape was also used to measure the height at the withers and the reference marks were the highest part of this and the pad of the hoof next to the heel. Nowadays, only the cane is used, because with the metric tape the measure of the height varies according to the muscular mass and the amount of flesh covering the horse at the time of the measurement.
The minimum height at the withers, measured with the cane, for a horse to be registered as breeding stock, or to pass the Basic Evaluation is 1.52 m (just under 15 hh) for Stallions and 1.50 m (just over 14.3 hh) for Mares. For those horses presented at the TQB, the minimum height at the withers, measured with a cane is 1.55 m 9just over 15.1 hh) for Stallions and 1.53 (just over 15 hh) for Mares.
This is determined by the distance between the foremost point that can be found (joint formed by the scapula and the humerus) and the ischial tuberosity or the rearmost point of the buttocks. this measurement is a longitudinal measure which is atken with the cane.
depending on these two parameters, height and scapula-ischial length, you can determine whether a horse is short-backed (height greater than length), medium-backed (height and length equal), or long-backed (height less than length.
Chest Height (Depth of Girth)
This is the distance between the highest point of the withers and the lowest point of the thorax coinciding with the region of the girth.
Height of the Sub-Sternal Space
Thsi is represented by the length between the lowest point of the thoracic cavity or point of maximum bend of the breastbone and the floor. As can be deduced, the sum of the chest height and the height of the sub-sternal space should equal the height at the withers.
In theory, there must be proportion between the chest height and the height of the sub-sternal space. When this proportion changes to favor the chest height, the horse is considered to be “close to the ground”. if, on the contrary, the proportion favors the height of the sub-sternal space, the horse is said to be leggy, “up in the air”. ” showing too much daylight” or “off the ground”.
This is determined by the lineal measurement that is carried out between the most laterally extended part on each side of the horse, at the height of the point of shoulder.
On occasion, the chest width is directly related to problems in the alignment of the forelimbs and as a consequence, to problems in movement. Horses with an excessively wide chest tend to have bowlegs in the forelimbs and dishing in movement. The opposite is when horses have a narrow chest and therefore tends to toe out.
Perimeter of the Thorax (Heart Girth)
This measurement is the longest around the barrel or thorax. It is measured with the metric tape totally encircling the thorax, by way of the girth, running from the lowest part of the withers, over the ribs, the girth area, to return to the point of origin.
A greater thoracic perimeter/heart girth measurement is desirable in mares, due to their breeding aptitude. A greater thoracic area is therefore a sign of beauty.
Perimeter of the Knee
When speaking of external conformation, of the exterior of the horse and when using the term knee, you are actually referring to the carpal joint and not to the stifle joint or the femur-tibia joint. This measurement is taken by encircling the carpal joint with the metric tape at its widest point.
Perimeter of the Cannon Bone (Bone Measurement)
This is obtained by encircling the lower third of the cannon bone with the metric tape.
Asign of beauty is that the horse gives you the sensation of solidity, of robustness and therefore that “they have bone”, but that they maintain their fine skin and giving the perception of quality. Years ago it was required that the minimum perimeter of the cannon bone should be 20 cm for the Stallions and 19 cm for the Mares.
All these measurements are merely statistical in nature, with the exception of height, which can also act to disqualify a horse. Those horses that do not reach the minimum height of 1.52 m (just under 15 hh) for Stallions and 1.50 m (just over 14.3 hh0 for Mares will not be ables to be registered as breeding stock. Additionally, those horses that do not exceed the height of 1.55 m 9just over 15.1 hh) for Stallions and 1.53 (just over 15 hh) for Mares, will not be eligible as Qualified Breeding stock.
Rafael Ortiz Alcala Zamora, Veterinarian, Conformational Competition Judge and Grand Prix Dressage Rider