Of all terrestrial mammals, the horse and the dog can both be considered to be among two of the most successful and diverse species to inhabit this planet. These species have each formed a symbiotic relationship with humans, ultimately becoming intimately entwined in our history and the development of our civilisation. Humans in turn are largely accountable for the development of hundreds of breeds of both horse and dog – each with their own unique conformational characteristics.
The domesticated dog, Canis lupus familiaris, has been linked with human civilisation for even longer than the horse. All modern breeds of dog originate from the wolf – Canis lupus. Research suggests that the separation of dogs and wolves took place over 27,000 years ago. The subspecies of wolf vary vastly in morphology (shape and form) over a wide range of climates and environments, from the giant Canis lupus arctos in the Arctic Archipelago to the smaller Canis lupus arabs on the Arabian Peninsula. Even ten thousand years ago, canine morphology was already diversifying. Skeletons from this era vary in size from 40cm to the size of a Great Dane; And it was during this era that humans began to select dogs for function.
Conformation is a term used to describe the general shape, structure and outline of an entity. The type of conformation observed in an animal will depend on the animals breed. Attempts to classify dogs according to variety began in the 18th century. Buffon & Daubenton’s classification comprised of four main categories; the mastiff, shepherd dog, scent hound and guard dog. Initially, the physical characteristics of a breed were determined by its occupation and the development of a pedigree breed was based on specific selected functional characteristics. Today, the modern day showing circuit has drastically influenced breeding. Features exclusive to a breed were selectively bred and ultimately became exaggerated characteristics, even if the trait is unnecessary or even detrimental to the health of the dog.
Dog breeds that have been selectively bred for function can have incredibly refined physical characteristics. Sight hounds have been developed for speed; a perfect example of this is the greyhound that has been carefully bred for thousands of years to create one of the fastest land mammals, capable of reaching 70km/hr. These dogs are vastly different in conformation to a dog bred for fighting, for example, the Pitbull Terrier. Greyhounds have a unique ‘rear – wheel drive’ pelvic limb mechanism, with hip extensor muscles designed for propulsion, fast acceleration and sprinting at high speeds. The traits which allow a dog to excel at running at high speed will make it less adept at a skill like fighting.
A study by Pasi and Carrier (2003) describe the functional trade-off seen in breeds who are highly adapted to either run or fight. Compared with dogs bred for fighting, the greyhound has a longer, lighter limb with reduced lower leg muscle mass, all to enhance maximum running speed. The Greyhound has more than 2.3 times greater capacity to use elastic storage and release of energy than a fighting dog. In addition, they have a greater hindlimb extensor muscle cross sectional area compared to the forelimb – a conformational feature opposite to that seen in the fighting breeds. Breeds developed to fight have shorter, stouter proximal limb bones that are larger in cross sectional area, more circular in shape and are more resistant to fracture than in the greyhound, a feature proposed to increase the animals’ ability to withstand the variable directional forces imposed on the limbs in fighting.
The conformation seen in dogs bred for hunting will vary depending on the environment that the dog was bred to hunt in. One of the desirable traits in gun dogs is speed, as well as many behavioural characteristics. Like the Greyhound these hunting dogs will have long, light limbs designed for speed. In contrast, other breeds designed to hunt have vastly contrasting conformation to the gun dog. For example the Dachshund was bred to flush out small prey from underground tunnels. There are nine different breeds of Dachshund which differ in size but share the common trait of short limb length.
Dogs may also vary in morphology within a breed, depending on the performance to which the animals have adapted to. Portuguese water dogs vary in conformation depending on the performance required of the dog. For example the dogs may have either a large pelvis with thin distal limbs or a smaller pelvis with thicker distal limbs and longer metacarpals and metatarsals depending on whether the breeder selectively bred for prowess in water based activities (swimming and pulling) versus terrestrial speed. This represents a functional trade-off between efficient speed and limb strength. Similarly, differences in conformation are seen in the Alaskan sled dog (mixed breed dogs) which are reflected in the various pursuits the dog excels in. The types of dogs which excel in sprint races have Pointer, Saluki, Borzoi and Weimaraner ancestors in their lineage, all of which excel in speed. Those which excel in endurance are those with Malamute and Husky ancestry.
Variations in spinal conformation may cause musculoskeletal issues in the dog. Chondrodystrophic dogs (Dachshund, Bassett Hound) are prone to intervertebral disc extrusion due to the extreme ration of back length to height at the withers. This may ultimately lead to pain, weakness and even paralysis. Cervical Spondylomyelopathy is a condition seen in large breed dogs such as the Doberman and the Great Dane. The combination of a rapidly growing animal and the morphology of a large heavy head with a long neck predispose these large breeds to increased strain on the vertebral column. Vertebral changes resulting from the increased forces can lead to spinal cord compression, resulting in the characteristic ataxic gait pattern which gives rise to the term ‘Wobbler’ syndrome.
As a physiotherapist, is it very important to be aware of the differences in conformation between various breeds and how a particular breed may be predisposed to various musculoskeletal, cardiorespiratory and neurological conditions. Awareness of conformation is important so that dog owners can be informed regarding the health conditions their animal may be predisposed to and educated as to what the signs and symptoms of a particular condition are. Most importantly, being informed will allow the owner to take action to prevent a particular condition from developing or progressing. There is a lot that we can do as pet owners to maintain our animals health and wellbeing, even when confirmation is less than optimal.