Why Some Horses Are Built for Speed and Others for Strength

The speed of horses has been renowned since time immemorial. Some horses were so fast that they served as the primary means of rapid transportation in the ancient world. Horse speed was such an important aspect of civilization-building that it has become a unit of measurement: horsepower. They are curious, smart, and often temperamental. Not all horses, however, have a need for speed. While draft horses are slow and steady, Thoroughbreds are fast and agile. But why?

It turns out there’s a lot of science behind the varied speeds of different types of horses. Besides entire industries built up around horse abilities, recent breakthroughs in science have identified the key genes that influence galloping speeds in select breeds. As such, let’s learn more about how genetics and selective breeding influence horse speed and the science behind it.

Horse History

The horse (Equus ferus caballus) has been around for about 45 million years, slowly evolving from small antelope-like creatures to the mighty steeds we see today. Humans and horses have an intimate relationship, one that started in 4000 BCE in central Asia. A millennium later and horse domestication was widespread. You can see why humans keyed in on wild horses as an animal that could be advantageous or helpful. They are large, powerful, and adapted to run while maintaining balance. Plus, their long backs are perfect for harnesses to hold seated humans.

Indeed, it’s uncanny how well horses can run and keep running. Shortly after being born, foals go from barely being able to stand upright to galloping and keeping up with their mothers. Once they get their sea legs, so to speak, horses move with four basic gaits: a walk, a trot or jog, a canter or lope, and a full gallop, which horses like thoroughbreds can max out at around 30-35 miles per hour. The transitions between these gaits are seamless thanks to the horse’s impeccable sense of balance. This is due to the unique physiology of their footing (their hooves never stop growing) and an almost sixth sense in the form of proprioception (a keen understanding of where their bodies and limbs are at any moment).

Genetics

The oldest horse specimen ever found, and moreover, the oldest successfully extracted DNA, came from the skeleton of a wild horse that lived between 560,000 – 780,000 years ago in the Yukon. Not only did scientists realize that modern horses were derived in part from a now-extinct group of wild horses, but also that Y-chromosomes found in modern domestic horses could be traced to just several stallions. The process of breeding horses, it seems, required a steady infusion of wild horses into domesticated herds. This helped spawn the various breeds of horses that exist today.

Selective Breeding

Horses may be built for speed, but it required thousands of years of artificial and selective breeding to produce modern variants like draft horses or thoroughbreds. Horses, by nature, are pretty temperamental. They are a prey animal, which means they have a reflexive fight-or-flight defense. Yet, simultaneously, they are quite curious and will temporarily shirk their prey classification to investigate things. As any cowboy will tell you, horses can sometimes lose it over nothing but a gust of wind.

Transforming a frenetic wild animal like a horse into a domesticated creature takes a long time and countless hours of training. At a base level, wild horses are selectively bred for their tolerance of and friendliness towards humans. From there, breeds diverge depending on their use by humans. Some horses are bred to survive harsh winter conditions, while others are bred for more delicate competitions like dressage. Many other traits, such as coat color, size, and behavior, have also been selectively bred. However, when it comes to speed, horses are generally grouped into three informal classifications, which are not scientific. There are over 300 breeds of horse, each one fitting fully or only partly into these general categories: hot-bloods, cold-bloods, and warm-bloods.

Hot-Bloods

A Polish aristocrat named Wenceslas Rzewuski came up with the classification of horses based on blood temperature in the early 19th century, and despite being completely inaccurate, his system stuck. All horses have the same body temperature, but ‘hot-blooded horses’ refers to several breeds artificially selected for their jumpiness, even anxiety, as well as liveliness and dexterity. Breeds like Arabian horses and Thoroughbreds are counted among the hot-blooded variants.

Hot-blooded breeds have a reputation for speed, endurance, as well as nervousness. Typically, such breeds are more diminutive than work-horse varieties. They are energetic, but by the same token, sensitive and acutely prone to stress. If any horse is going to freak out at a moment’s notice, it will likely be one classified as “hot-blooded.” Thanks to their speed, however, hot-blooded breeds like thoroughbreds are often used for equestrian sports and racing. Be it in show-jumping, dressage, or all-out races, hot-blooded breeds excel.

Cold-Bloods

While hot-blooded breeds are fast and jumpy, cold-blooded breeds are quite the opposite. They are big-boned, big-bodied, but calmer and more collected—gentle giants, in a way. Breeds like Percherons, Clydesdales, and Belgian horses fall under the cold-blooded category. They are often very large and put to work. Over centuries, cold-blooded breeds were selectively bred to work in draft and agricultural arenas. They are imposing, but quite calm under pressure.

Warm-Bloods

Warm-blooded horse breeds are like fusion cuisine, a happy medium between disparate characteristics. Whereas hot- or cold-blooded horses are designed for specific purposes, warm-blooded breeds are more jack-of-all-trades; they can be used for riding or even drawing wagons. Breeds like Dutch Warmbloods, Hanoverians, and Holsteiners are examples of warmbloods. They are typically bigger than Thoroughbreds and calmer, but can still function in disciplines like dressage and eventing. If you ever visit New York City and see a police officer on a horse, it will likely be a draft-cross breed, such as a Percheron-Thoroughbred cross, rather than a pure cold-blooded breed like a Clydesdale.

The Science of Speed

For millennia, horse breeding was a long, drawn-out process of trial and error. A breeder found a strong stallion and paired him with a suitable mare, crossed their fingers, and sort of hoped for the best. Refining a breed for speed could take decades, even centuries, with plenty of false starts along the way. In recent years, however, scientists have uncovered the key genes that make breeds like Arabians or Thoroughbreds so fast.

A 2022 study published in the “Communications Biology” Journal suggests that a core set of genes act as “key drivers of the racing phenotype.” It seems that galloping horse breeds feature a set of genes that influence athleticism and racing performance, despite said breeds originating from diverse locations and backgrounds. The study suggests that understanding the variations in these genes may be used to refine horse populations towards specific styles of racing.

We Have the Technology

Horse breeding used to be guesswork, but now it’s a real science backed by technology. Advancements in genome sequencing, as previously mentioned, help pinpoint the traits breeders are looking for. Nowadays, breeders can analyze a foal’s DNA and discover exactly what kind of horse it will be. Focusing on the Myostatin gene allows breeders to classify growing horses as sprinters, middle-distance runners, or marathoners. For example, horses with “CC” variants will do well speeding in short bursts, while horses with “TT” variants will succeed with longer distances.

With the advent of AI, breeders can now use technology to uncover previously elusive breeding patterns in champion racehorses. Everything from biomechanics like stride efficiency and gait mannerisms to genetic compatibility between pair members can now be factored into a breeder’s quest for the ultimate racehorse. Other innovations like CRISPR, too, will likely factor into the future of horse breeding. Horses like Seabiscuit or Secretariat were so fast and skillful that they seemed like genetic flukes or supernatural. With the advent of modern technology and the science to back it up, the future of horse racing will likely produce Thoroughbreds capable of incredible speeds.

The post Why Some Horses Are Built for Speed and Others for Strength appeared first on A-Z Animals.