A Veterinarian’s Viewpoint.
by Barbara Corson
Of all the many tools that have shaped human cultures, harnessing* systems for domestic animals are among the most important. (*Note: Some people differentiate between harness and yokes, but in this article, harness is used in the sense of capturing or transmitting power, as one would “harness the energy of the sun”.) Animal power (or its lack) has been a significant factor in how cultures developed everywhere.
Many different harness systems have been developed in the cultures that had access to draft animals, but every harness system needs to take the anatomy of the draft animal into account. A knowledge of the anatomy of horses and cattle can help in understanding the different harness systems that have developed for using these two species as draft animals. This article is the result of my observations as a veterinarian and as a “hobby” teamster of both cattle and horses. It touches on some of the more easily illustrated concepts.
The Neck Bones
Both horses and cattle have seven cervical vertebrae, but in other ways the necks of the two species are quite different: in cattle the neck is relatively short and carried more or less horizontally.
The individual vertebrae are irregular in outline. C-4 through C-7 are short (in the head-to-tail axis) and have finger-like dorsal processes.
In horses, the seven bones are usually more vertical. They normally form a slight S-curve (or a Z, if you are looking at the neck from the left side!). The curvature allows horses to “telescope” (shorten and extend) their necks more than cattle can. This curvature is part of good conformation, whether the horse appears to have a short thick neck or a long, slender one.
Compared to the bovine neck bones, the equine cervical vertebrae are longer and the outlines are relatively regular, with no elongated dorsal processes.
The soft tissues of the neck: the nuchal ligament and muscles of the neck:
The nuchal ligament is a connective tissue* structure that covers the tops of the thoracic vertebrae and extends to the back of the skull, with branches that extend to the cervical vertebrae. (*Note: Connective tissues include ligaments, tendons, and cartilage. All three tissues have similar cellular make up but they have different functions. Ligaments by definition join bones together; their general purpose is to hold bones in place and limit movement. Tendons, in contrast, join bone to muscle and their function is to move bones/ joints.) In cattle, both the cord-like top portion as well as the cervical extensions of the nuchal ligament are thicker and more robust compared to the horse. There is relatively little muscle or fat tissue in the neck of taurine cattle (with the notable exception of mature bulls), but the intermingling of muscle and fat tissue in the nuchal ligament is a characteristic of zebu cattle.
In the horse, the cervical extensions are sheet-like and are normally layered with fat and muscle tissue. The ligaments, fat and muscle tissue combine to form the horse’s crest, which is normally very firm. Some breeds characteristically have thick, heavy crests, and stallions in general develop thicker crests than mares or geldings of the same breed.
This part of the body is formed by the dorsal spinal processes of the thoracic vertebrae. In quadrupeds, the tall dorsal processes act like the tower of a suspension bridge; they are important in supporting the muscles of the neck and shoulders. The withers are also an important landmark in harnessing systems; in fact, the English noun* withers derives from Old English “widder”, meaning ‘against, contrary’ i.e., the part of the animal that is against the yoke or collar and that opposes the load. (* Not: not to be confused with the English verb “wither,” which is a homonym meaning to shrink, dry or shrivel.)
In cattle, the first thoracic vertebra has a long dorsal process (see figure 2; the first thoracic vertebra is labeled “18”). In the horse, on the other hand, the dorsal process of T1 is much shorter (see Figure 4; the first thoracic vertebra is labeled “24”). The difference in the height of T1 can generally be seen in horses and most taurine cattle when the head is lowered, for example for grazing.
The projection of the first thoracic vertebra means that in cattle, the withers are further forward relative to the shoulder than in the horse. In horses, the withers are between the shoulder blades, but in cattle the shoulder blades are caudal to the withers.
The structure of the bovine neck and withers forms a natural seat for a yoke…
The short horizontal neck carriage of cattle means that they can also be effectively harnessed using various types of head yokes.
Muscles of the shoulder and chest
Although there is a lot of variation depending on breed and level of fitness, in general, horses are built to be able to run long distances, and to rear and strike with their front legs. In order to do these things, horses need well developed muscles that move the shoulder blade. Horses are also built to be able to stand for long periods without wasting energy, and to accomplish this, they have large pectoral and triceps muscles, as well as a system of interacting tendons and ligaments collectively called “the stay apparatus”, which allows them to rest while standing. As a result of these muscular adaptations, the shoulder of a horse is normally tightly bound to the chest wall and there is a well-defined ledge of muscle that serves as a “collar bed.”
Cattle have their own kind of athleticism, but they have not evolved to survive by running, rearing or striking with their forelegs. Instead, the bovine neck and shoulder muscles are well suited for “head wrestling” with opponents, whether predators or other cattle. Bovines also lack the stay apparatus and are not able to rest standing up, at least not any better than a dog or a human. One of the results of these adaptations is that in cattle, the neck and shoulder muscles form only a shallow ledge and are more loosely attached to the torso than in the horse.
The bones of the chest
As far as harness systems go, the most important “chest bones” to consider are the shoulder joint (the point of the shoulder) and the sternum (the point of the breast). As the names suggest, these structures stick out (like points) and they are not padded with much muscle or fat. Bones and joints that are covered only with skin are not able to take much pressure without tissue damage and pain, and so harness systems have to avoid these areas if the draft animal is going to stay functional.
The next figures show the structures of the chest with the point of the shoulder marked with a red circle and the point of the breast (a.k.a. the brisket in cattle) marked with a yellow “x”. In cattle the point of the shoulder is closer to the spine (marked as a blue line in the photographs) than in the horse, and the distance from the spine and shoulder to the the sternum is longer.
In both horses and cattle, the point of the breast is important because it is a palpable landmark for another vital structure: the thoracic inlet. This is where the windpipe and other vital structures pass into the chest cavity. Pressure from a harness in this area can affect the animal’s breathing and blood circulation. In horses, the thoracic inlet is usually higher in relation to the overall depth of body. In cattle, the thoracic inlet is longer and extends below the animal’s elbows.
Textbooks of anatomy are a good starting point, but there is of course a lot of variation in the way animals are “assembled” and the relative proportions of body parts and angles of joints. Here are two horses with different neck and shoulder conformation. In both photographs, the point of the shoulder (pS) is in red, and the point of the breast (pB) is in yellow. The axis of the shoulder blade and humerus are shown as blue lines.
How would harnessing the horse in figure 21 be different than harnessing the one in figure 22?
I made this table to summarize the article:
|Little development except in bulls
|well-developed muscles, intermingled with fat, form the crest
|T1 – T4; in front of shoulder blades
|T 4 – T6; between shoulder blades
|Shoulder and chest muscles
|muscles that hold the shoulder to the torso are less developed and the junction between shoulder blade and torso is looser
|More development of muscles that move the shoulder blade and keep front legs straight; junction between shoulder blade and torso is tight.
|a.k.a. brisket; large and flat
|a.k.a. point of the breast; curved and sharp-edged
The anatomy of cattle and especially horses has long been studied but is never easy to summarize. What is left out of a summary may be as important as what you include. Beyond anatomy, there are many other factors that affect draft animal harness systems, including physiology and temperament of the animals, climate and cultural traditions. In other words, there is plenty of scope for further articles on the subject. I hope other authors will contribute their perspectives and insights in future articles.
Anatomy diagrams 7, 12 and 16a are from:
Sisson and Grossman’s Anatomy of the Domestic Animals, 5th Ed.; Robert Getty DVM; W. B. Saunders Co; 1975
All other anatomy diagrams are from:
Topographical Atlas of the Domestic Animals; Peter Popesko; W. B. Saunders; 1975
Both books are in the Public Domain
[A German language translation of this article can be downloaded from the Arbeitsgruppe Rinderanspannung website. – Ed.]