How To Read Your Horse's Test Results: Ancestry, Composition, and More

You have likely heard of the various commercially available DNA tests for dogs that tell you their breed makeup. You know, the one your “dog-mom” friend posted all over social media about how her pooch, Fluffy, is 50% this, 50% that, but 100% adorable? Etalon Equine Genetics offers a similar, yet more applicable and actionable Ancestry Package DNA test for horses!

Etalon’s Ancestry Package DNA test is an in-depth comparison of your horse's genetic makeup and how it is like, or unlike, other horses within various "breeds," disciplines, and populations around the world. Relatives, like your horse’s parents, siblings, aunts, uncles, and close cousins may also be identified and appear in their online family tree with the Find My Herd and Horses Like Me tools available in the Etalon dashboard. The journey begins by using a "reference" population; meaning a population of horses that have previously been analyzed and compared to one another for genetic similarity and difference.

You supply your horse’s DNA from a pulled hair sample - way easier than swabbing their cheek! Etalon compares your horse's genetic makeup (the “mystery” horse) to an established reference horse set ("known" horses) and provides information on what your horse has in common with each reference horse and their genetic group as a whole. You will receive a complete report on your horse’s unique genetic Breed Composition, Genomic Inbreeding Value, Thoroughbred “Blood” Percentage (or “% Blood”), as well as the options to use our Find My Herd and Horses Like Me tools. Let’s take a look at what all of that means!

Breed Composition

Etalon’s Ancestry Package testing for horses involves a comprehensive examination of your horse's genetic makeup and how it relates to, or overlaps with, other horses within different breeds, regions, disciplines, and populations worldwide. By uncovering a horse's ancestry, the analysis provides valuable insights into the horse's characteristics and potential suitability for specific purposes. You can learn more about the breed compositions here!

The analysis also delves into regional breeding practices and the natural evolutionary changes in horse populations. Horses from distinct regions or specific groups share genetic similarities or content, which can be identified, compared, and visually represented on a graph. The genetic makeup of closely bred horses, whether due to geographic proximity or intentional human-directed breeding selection for particular disciplines or needs, can form identifiable clusters on the graph. These clusters often align with traditional breed labels or clusters, showing a correlation between DNA and established breed classifications.

It is important to note that this is not a test to determine your horse’s breed. Dr. Samantha Brooks, an associate professor at the University of Florida, explained why in an episode of our podcast, Unbridled Genetics, all about ancestry testing. “The biggest reason there really isn’t anything that can be called a ‘breed test’ in the horse, although genetics is phenomenal for tracking ancestry, is because we as horse owners and breeders cannot decide what a breed is.” Breeds are often defined through a political or historical lens, but that does not necessarily line up with the “biological truth,” as Dr. Brooks calls it. She uses the example of a registered American Quarter Horse versus an American Paint Horse. A significant amount of their ancestry is shared and both genetically belong to the stock horse group, however culturally speaking, these can be considered two different breeds.

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 a breed of horse from known populations in comparison to the horse that was tested by Etalon.

Registries, well-defined breeds, or closed groups with longer historical breeding records typically display more distinct and defined gene clusters. Dr. Brooks 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 well-established horse populations to evaluate an accurate representation of your horse’s ancestry as opposed to trying to report that your horse is definitively one or more relatively new breeds.

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 and indicates where the tested horse aligns within this genetic landscape, offering a visual representation of its genetic relationship to various horse populations.

Genomic Inbreeding Value

Ancestry testing plays a crucial role in addressing the concern of inbreeding within horse breeding practices. Inbreeding, historically a consequence of limited horse populations, involves breeding closely related animals over multiple generations. While it was somewhat inevitable in the past due to fewer available breeding options, the landscape has changed drastically. With advancements in genetic testing, breeders now have the opportunity to be more discerning, aiming to enhance genetic diversity and optimize their horses’ future performance.

One recent study that focused on Thoroughbreds has illuminated the adverse effects of inbreeding on performance. This research found a direct correlation: a 10% increase in inbreeding led to a 7% decrease in the likelihood of a horse ever participating in racing. Put simply, this means that as the amount of inbreeding goes up, performance goes down.¹

Etalon’s ancestry testing goes beyond conventional pedigree-based estimates of inbreeding. It provides a "Genomic Inbreeding Value," evaluating a horse's inbreeding based on their actual genetic content as opposed to the more commonly used inbreeding coefficient which is a calculated estimate based on a horse’s reported pedigree. Two full siblings from the same parents will show the same inbreeding coefficient using the traditional pedigree estimate when, in reality, their individual DNA can reveal a very different story. It would be like saying you are exactly like your sibling, which you obviously aren’t because we don’t inherit the exact same genes from each parent, and neither do horses. It’s best to base this figure on actual genes inherited!

For instance, consider two broodmares who are full sisters—sharing the same parentage and pedigrees—yet displaying varying genomic inbreeding values. Armed with this precise genetic information, a breeder can make informed decisions. Opting to investigate breeding pairs that reduce a foal’s potential inbreeding value contributes to enhancing the genetic makeup and diversity of future foals. We can even take this one step further by looking at your horse’s unique inbreeding value compared to a potential mate’s inbreeding value and using our platform, provide a predicted inbreeding value for their foal.

In the example below that examines a group of Warmbloods you’ll notice that the genomic inbreeding value varies greatly between two foals from the same sire. One explanation for this is the assumption that each foal came from a different dam, however, two full siblings (both from the same dam and sire) may have very different inbreeding values based on the genetic content they each inherit. For instance, one foal may inherit similar or overlapping genetic content from his sire and his dam resulting in an increased value, versus the second foal, who may inherit two very different or non-overlapping shares of genetic content from the same sire and dam resulting in a lower inbreeding value. The trick is to remember that some horse parents (the sire and the dam) are related further back in the pedigree and may, unknowingly, share a large chunk of the same genetic content. If they both pass that on to the foal, they are doubling up on that same content, thereby increasing the inbreeding value.

This utilization of ancestry testing empowers breeders to make strategic choices, prioritizing horses with lower genomic inbreeding values to cultivate a more diverse and robust genetic pool. Ultimately, this selective breeding approach aims to optimize the genetic potential and performance of future generations, mitigating the adverse effects associated with inbreeding in horse populations.

Thoroughbred Blood Percentage

The concept of Thoroughbred Blood Percentage, often referred to as "% Blood" in Eventing circles, is another crucial factor measured by Etalon's ancestry testing. This percentage signifies the genetic resemblance shared with a known Thoroughbred reference population.² It serves as a genetic marker and holds significance, particularly within Eventing, impacting a horse's capabilities and requirements asked of them across the three diverse disciplines. Etalon's method of measuring this percentage genetically often reveals variations of up to 30% when compared to traditional pedigree calculations - that’s huge!

Pedigrees offer an estimation of genomic data, assuming an equal 50% genetic contribution from each parent in every breeding instance. However, the reality involves "recombination events" during reproduction, leading to diverse genetic inheritances among siblings. For each gene, one allele is inherited from each parent. In the instance of heterozygosity, where the sire and/or dam carry two different alleles, that’s two or three more genotype options versus two homozygous parents who can only create one genotype for that gene. Each allele combination for each gene has its own chance of occurring; multiply that across 2.7 billion base pairs, and all of a sudden there is an infinite number of possibilities to make up one horse, let alone two! This phenomenon, observed in both humans and horses, results in varying ancestry percentages between full siblings, challenging the accuracy of pedigree-based estimations.

Genomic measurement, utilizing a horse's DNA to directly assess its genetic makeup and compare it against the Thoroughbred population, provides a significantly more precise evaluation. In contrast, a horse's pedigree merely serves as a proxy for this genetic information. With the availability of genetic testing, the reliance on pedigree-based analysis for crucial breeding decisions is becoming obsolete, given the higher accuracy and reliability of genomic data.

Let’s take a look at Tsetserleg: if we calculate his % blood based on his pedigree, we would expect to see a Thoroughbred Blood Percentage of 47%. However, upon DNA testing, it was revealed that he actually possesses a significantly higher percentage, totaling 62% Thoroughbred, which is more in line with his observed performance! This substantial difference underscores the importance of accurate genetic assessment. The Thoroughbred Blood Percentage significantly influences a horse's performance across various disciplines, especially on the demanding cross-country field.

Understanding your horse's true genetic makeup through genomic assessment enables you to make more informed breeding decisions, performance predictions, and tailored training strategies. The discrepancy between pedigree-based estimations and actual genomic measurements highlights the limitations of traditional methods, emphasizing the necessity of embracing advanced genetic testing to optimize breeding outcomes, performance capabilities, and enhance a horse's competitive potential.

Find My Herd

The exploration of familial ties through tools like "Find My Herd" presents an exciting opportunity to unearth the intricate genetic pedigree of your horse. This one-of-a-kind digital platform enables the discovery of immediate and extended equine relatives, building a comprehensive DNA-based lineage that you may not have had access to before.

In this interconnected web of familial relations, your horse's genetic heritage extends beyond just the immediate parents, siblings, and offspring. Our growing database of horses encompasses a network of relatives, spanning across generations and branching out to include grandparents, cousins, aunts, uncles, and even further extended family members! Each result will show up in your horse’s results as an interactive circle that allows you to explore that horse’s profile so you can learn even more about your horse’s relatives.

Visualizing this genetic pedigree creates a vivid digital representation of your horse's lineage, showcasing the complex network of relationships and genetic influences that have shaped your equine companion. This comprehensive understanding serves as a bridge, connecting you more intimately with your horse by providing insights into their genetic heritage.

By delving into these connections, you stand to gain a deeper understanding of the genetic contributions that created your horse. This knowledge fosters a sense of appreciation for the unique traits, abilities, and characteristics inherited from various relatives within your horse’s family tree.

Understanding the broader familial context enriches the horse-owner relationship, allowing for tailored care, training, and management practices that acknowledge and leverage the genetic legacy embedded in your horse's lineage. It's not just about knowing the immediate family members; it's about embracing the entirety of the equine lineage to better appreciate and nurture the individuality of your horse.

Horses Like Me

Our Horses Like Me tool represents a groundbreaking advancement in the realm of equine genetics, offering an innovative tool to identify horses that share significant genetic similarities with your own regardless of how closely related they may or may not be. This pioneering genetic platform transcends the conventional boundaries of pedigree or direct lineage, revealing counterparts with akin genetic traits or shared breed affiliations that are defined by a horse’s composition compared to known populations.

The horses identified by Horses Like Me possess genetic compositions akin to your horse, regardless of direct familial ties. Their similarity in genetic makeup implies a potential relationship, capability, or association, showcasing either a shared classification within a particular breed, discipline, or genetic kinship.

A higher percentage of genetic similarity between horses hints at a closer relationship or potential common ancestry. It suggests a horse shares a substantial portion of genetic markers associated with a specific breed. A higher percentage here may also suggest a possible relative that is further removed within the equine world.

On the other hand, lower percentages of genetic similarity highlight shared genetic elements that might link back to common ancestors within recognized breed reference groups like Thoroughbred, Arabian, or other established lineages. These percentages provide valuable insights into the presence and extent of particular breed influences in your horse's genetic makeup.

The Horses Like Me tool differs from the Find My Herd tool in that it facilitates the exploration of equine counterparts that go beyond traditional familial ties, providing a panoramic view of horses sharing common genetic threads. Horses Like Me also populates genetic matches as interactive circles similar to the Find My Herd tool so that you can learn more about the horses with similar genetic makeups. It opens doors to discovering horses whose genetic composition closely aligns with your own without being related, offering opportunities to explore potential broad-range ancestral connections, breed affiliations, or shared genetic traits.

Understanding these genetic similarities widens the perspective on your horse's genetic heritage, offering insights into potential connections within the equine community. It enables owners, breeders, and enthusiasts to uncover valuable information about their horse's genetic predispositions, historical ties, and potential relationships, ultimately fostering a deeper appreciation and comprehension of their equine companions.

Etalon’s Ancestry Package represents a paradigm shift in comprehending the genetic makeup of horses. Through groundbreaking tools such as Find My Herd and Horses Like Me, our DNA tests transcend conventional pedigrees, offering intricate insights into equine lineage and potential relationships among horses across an individual and worldwide stage.

Our genetic testing and analytic tools provide you with comprehensive data beyond breed composition, supplying detailed assessments of inbreeding risks and precise Thoroughbred Blood Percentages. They serve as invaluable resources, empowering owners and breeders to make informed decisions crucial for breeding outcomes and optimizing equine performance.

The depth of information obtained isn’t merely for amusement; it serves as a strategic advantage in the world of horse breeding and care. Armed with this comprehensive genetic profile, equestrians of all backgrounds can make calculated decisions to enhance their horses’ lineage, health, and performance. This advancement in equine ancestry testing underscores a pivotal moment in horse care and breeding, ushering in a new era of informed practices and enhanced understanding within the equestrian community.

Resources

“Betting on Innovation: Horse Ancestry with Dr. Samantha Brooks” from Genetics Unbridled - Horse DNA & Technology Powered by Etalon Equine Genetics

¹ Hill, E. W., Stoffel, M. A., McGivney, B. A., MacHugh, D. E., & Pemberton, J. M. (2022). Inbreeding depression and the probability of racing in the Thoroughbred horse. Proceedings of the Royal Society B: Biological Sciences, 289(1977). https://doi.org/10.1098/rspb.2022.0487.

² 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