How to Read Your Horse's Test Results: Breed Composition

Welcome to our in-depth exploration of breed compositions found in the Ancestry, Composition, and Breed Analysis Test! Understanding your horse's genetic composition is like peeling back the layers of a captivating story written in DNA. In this guide, we'll walk you through the key elements of breed composition providing you with the tools to decipher your horse's unique genetic code.

Genetic Composition Key

Etalon utilizes seven distinct equine 'breed' populations to determine your horse’s ancestry. These seven groups are a condensed version of the reference populations defined by a collective study on the genetics of horse breed origin and contain overlapping breeds from the same global regions.1 These groups are used because they typically boast longer historical breeding records, which causes them to exhibit more distinct and defined gene clusters compared to the numerous breeds we recognize today. The variety of newer breeds often shares similar ancestry, like the American Quarter Horse versus the American Paint Horse for example. These breeds may lack the same depth of historical data, resulting in less clear and comparable genetic groups.

This is why Etalon’s Ancestry, Composition, and Breed Analysis test focuses on these seven well-studied horse populations to most accurately evaluate your horse’s ancestry, rather than attempting to definitively identify it as one or more relatively new breeds.

With that in mind, let’s take a deeper look into the seven breed populations that you may encounter on your horse’s ancestry report!

Thoroughbred

The Thoroughbred breed has its own category thanks to centuries of selective breeding and meticulous recordkeeping to create high-quality racing animals. The Thoroughbred was also later used to create many of the breeds we know and love today such as stock-type horses, like the Quarter and Paint horse, and various Warmbloods. Thoroughbreds were developed by crossing English mares with one of three foundation stallions over the seventeenth and eighteenth centuries in England when horse racing was growing in popularity. The Jockey Club of Britain, founded in 1750, created The General Stud Book in 1791 to record the pedigrees of Thoroughbreds. As Thoroughbred horse racing expanded across the globe, so did their stud books. The American Stud Book, first privately published in 1868 and later bought by The Jockey Club (US) in 1896, was created to separate European and American Thoroughbreds. Both stud books are closed registries. This means that a foal is only eligible for registration if its pedigree can be completely traced back to horses that are included in The American Stud Book, The General Stud Book, or an approved foreign stud book. In terms of ancestry genetics and reading your results, this means that Thoroughbreds have a distinct genetic fingerprint because of their selective breeding history which makes them a great population to use as a comparison tool.

Iberian

Breeds in the Iberian category include the Andalusian, Mangalarga Paulista, Lusitano, and Puerto Rican Paso Fino. As the name implies, horses that fall into the Iberian ancestry category are native to or have their roots firmly planted in the Iberian peninsula of Southwestern Europe. Bloodlines for some Iberian breeds, such as the Pura Raza Española (PRE), can be traced back as far as the early eighteenth century, making them ideal candidates for creating a distinct genetic cluster, and by extension, forming their own group on the PCA map (see below!).

Carriage Horse

The Carriage Horse group includes the breeds such as the Saddlebred and Standardbred. Carriage Horses trace their roots back to the seventeenth and eighteenth centuries and are the product of various Thoroughbred crosses primarily in the “New World” Americas. Like their Thoroughbred ancestors, this category of horse was also bred for racing but was mixed with horses that were known for their comfortable intermediary gaits, causing them to excel as harness racing horses. Carriage Horse breeds are often gaited horses because they were selectively bred for their additional gaits such as the rack or pace.

Exmoor

Exmoors, similar to Thoroughbreds, enjoy a category all their own due to a longstanding history of selective breeding that creates a distinct genetic cluster. Unlike the Thoroughbred, however, this resulted from geographical constraints versus human-dictated breeding for performance. For centuries, the wild Exmoor pony was secluded to only its native British Isles. This made it incredibly difficult for them to increase their overall genetic diversity by reproducing with horses from other ancestral backgrounds.

North Sea

The better-known horse breeds of the North Sea region include the Norwegian Fjord, Icelandic, North Swedish, and Shetland pony. Horses of the North Sea region are some of the oldest breeds known to man. Icelandic horses descend from a small gene pool that was created by laws in 982 AD that forbid the importation of horses to prevent disease. Archaeological findings indicate that horses such as the Norwegian Fjord were likely selectively bred for at least 2,000 years. Shetland ponies have roamed the Shetland Islands of the United Kingdom for at least 4,000 years. It is their shared extensive histories of geographical and human-directed selective breeding that have created an apparent genetic cluster for the horses of the North Sea.

Near East

Horse breeds in the Near East group include the Arabian, Akhal-Teke, and Caspian. These breeds are known for their athleticism, both in speed and stamina. Despite their refined conformation, these horses are also known for being incredibly hardy. Similar to the horses of the North Sea, the horses of the Near East have also been around for thousands of years which has created their distinct genetic signature. The Arabian horse was first depicted in ancient Egyptian art more than 3,500 years ago, but it was the Bedouin people of the Arabian desert who refined this breed into what it is today. The Akhal Teke, a descendant of the raiding horses of Turkmenistan, was first described over 3,000 years ago. Archaeological expeditions have dated the rare Caspian horses of present-day Iran back to 3,400 BC.

European Heavy Horse

The European Heavy Horse category includes the Belgian, Clydesdale, Percheron, Freiberger or Franches Montagnes, and Fell Pony. Belgian horses were officially given their name in 1885 when influential breeders in Belgium combined the longstanding studbooks of two prominent heavy-type horses, the Flemish horse, and the Brabant. The Flemish horses of Belgium were in great demand throughout the 1700s as both war and carriage horses, causing them to be exported across Europe and ultimately serving as a foundation for the Clydesdale and Shire in England whose studbooks were first published in 1877 and 1878 respectively, and the Percheron in France whose official studbook dates back to 1893.

Composition Map

The Composition Map is like a genetic travelogue for your horse! It gives you a cool visual of where each category of horse hails, breaking down their DNA roots in a way that's easy to grasp and see. Picture it as a snapshot of your horse's family tree, but on a global scale. Now, let's circle back to those horse groups we talked about earlier – the map paints a vivid picture, aligning each group's backstory with the actual places on our planet where their genes originated.

This map isn't just about science; it's about exploring the world your horse's genes have journeyed through. It's a bit like having a passport for your equine friend! Each category becomes a mini history lesson, showing you the connection between where these horses roamed in the past and where their genes have left their mark today.

Whether you're a seasoned horse pro or just a curious enthusiast, the Composition Map is a game-changer. It turns complex genetic details into a fascinating story, connecting your horse to its global roots. It provides a world map for your equine partner's DNA adventure – and who wouldn't want to explore that?

Reading the PCA Chart

The visual representation in the scatter plot (referred to as a Principal Component Analysis or "PCA" chart) below aids horse owners or breeders in understanding the genetic heritage of their horse, shedding light on its lineage, potential capabilities, and the possible suitability for specific tasks or disciplines based on its genetic composition. Each static dot on the scatter plot represents the genetic makeup of an actual individual horse included in the original study. Those individual horses were reported as “x” breed of horse from known populations and are used in comparison to your horse within the Etalon Ancestry database.

Registries, well-defined breeds, or closed groups with longer historical breeding records typically display more distinct and defined gene clusters. Dr. Samantha Brooks, associate professor at the University of Florida, uses the example of the genetic ancestries of a Clydesdale versus a Shetland pony. “Those horses had fairly different geography and much different selective pressure for thousands of years, so that gave time for biology to really separate the two populations.” Many breeds we know of and track today do not currently have this same depth of historical data to create clear genetic clusters. This is why Etalon’s Ancestry, Composition, and Breed Analysis test looks at the well-established horse populations discussed above to evaluate your horse’s ancestry.

The clusters formed by defined equine populations are frequently separate from most other horse samples, showcasing the genetic uniqueness and historical lineage of particular groups. Proximity or purposeful breeding for specific disciplines can cause genetic content to cluster together, while less related horses appear in more distant regions. The scatter plot provided in the results illustrates the reference horse population. It indicates where the tested horse aligns within this genetic landscape, offering a visual representation of its genetic relationship to various horse populations.

Breed Composition Examples

Are you excited to uncover the secrets hidden in your horse's ancestry report? Let's dive into some fascinating examples that showcase the diverse ancestry compositions of both well-known and unique horse breeds! Get ready for a journey through the genetic tapestry of these magnificent animals, shedding light on the remarkable stories embedded in their DNA.

References

¹ Petersen, J. L., Mickelson, J. R., Cothran, E. G., Andersson, L. S., Axelsson, J., Bailey, E., Bannasch, D., Binns, M. M., Borges, A. S., Brama, P., Machado, C., Distl, O., Felicetti, M., Fox-Clipsham, L., Graves, K. T., Guérin, G., Haase, B., Hasegawa, T., Hemmann, K., . . . McCue, M. E. (2013). Genetic Diversity in the Modern Horse Illustrated from Genome-Wide SNP Data. PLOS ONE, 8(1), e54997. https://doi.org/10.1371/journal.pone.0054997