Why arabian horse

It defies simple interpretation. When we first encounter the Arabian, or the prototype of what is known today as the Arabian, he is somewhat smaller than his counterpart today.

Otherwise he has essentially remained unchanged throughout the centuries. Authorities are at odds about where the Arabian horse originated. There are certain arguments for the ancestral Arabian having been a wild horse in northern Syria, southern Turkey and possibly the piedmont regions to the east as well. The area along the northern edge of the Fertile Crescent comprising part of Iraq and running along the Euphrates and west across Sinai and along the coast to Egypt, offered a mild climate and enough rain to provide an ideal environment for horses.

Other historians suggest this unique breed originated in the southwestern part of Arabia, offering supporting evidence that the three great river beds in this area provided natural wild pastures and were the centers in which Arabian horses appeared as undomesticated creatures to the early inhabitants of southwestern Arabia. Because the interior of the Arabian peninsula has been dry for approximately 10, years, it would have been difficult, if not impossible, for horses to exist in that arid land without the aid of man.

The domestication of the camel in about B. The Arabian horses form a cluster that is clearly separated from most other horse breeds, with the exception of horses of the rare Dareshuri and Kurdish breeds from Iran Fig.

The Arabian cluster is also broad, particularly in the PC1 dimension, suggesting a high level of genetic diversity within the global Arabian population. The other breed with a similarly broad cluster across the PCA was the American Quarter Horse, a breed notable for its division into several subgroups that also cluster separately in PCA 23 and differ in the frequency of alleles determining susceptibility to recessive inherited diseases In our analysis, the Quarter Horse samples displayed diversity across PC2.

Finally, the Arabian cluster appears distinct from the Thoroughbred cluster, with the exception of a small number of Arabian horses that will be discussed below. The Arabian is a distinct breed with diverse lineages, having little apparent relationship to the Thoroughbred. Principal component analysis of Arabian horses sampled in this study A among a reference set including samples from 18 additional global breeds from 13 and 22 , with symbol shape indicating data source and symbol color indicating breed data set: samples across 30, SNPs ; and B with 71 Persian Arabian and 11 Turkemen samples from 13 , and 17 Thoroughbred samples collected in this study, with symbol shape indicating breed, and symbol color indicating Arabian breed lineage, except for the Thoroughbred and Turkemen groups data set: samples across 56, SNPs.

PC3 is plotted in Supplemental Figs. S2 and S3. See also Supplemental Fig. To investigate relationships among Arabian horses of unique identifiable lineages, we applied PCA to just the Arabian population of samples collected in this study, with the addition of the 71 Persian Arabian samples from Iran 13 , and included Thoroughbred this study and Turkemen samples 13 as out-groups analysis data set: 56, SNP genotypes from samples.

In general, the horses from the same lineage tend to cluster together, with the Straight Egyptians separating far from the main cluster Fig. As expected, the horses of multi-origin ancestry are scattered across the PCA plot. Among the samples collected in this study, we identified a subset of Arabian horses with publicly available performance records from participation in competitions.

We reexamined the PCA results in the context of these different types of competitive events. As shown in Fig. Horses used for endurance races tended to be drawn from the Polish and multi-origin clusters. Finally, many of the Arabian horses used for flat racing were placed in PC space closer to the Thoroughbred cluster Fig.

This relationship may have historical significance and warrants further investigation. The Arabian breed shows genetic differentiation associated with performance use. Principal components in Fig. Arabian samples were color coded by use type of competition in endurance competition, flat course racing or show. Racing horses orange plot in the PCA space between the Thoroughbred racehorse and other subgroups of Arabian horse.

The Thoroughbred breed, a logical comparison based on written history, appears relatively homogeneous within breed, consistent with the closed breeding practices recorded in the Thoroughbred studbook since the late s Fig. In contrast, individual horses from Middle Eastern countries, including Iran, and the large group of horses outside the Middle East and with well-documented recent multi-origin ancestry, show varying degrees of admixture across the K- populations.

A subset of multi-origin ancestry horses possesses an unusually large proportion of shared ancestry with the Thoroughbred Fig. Individual lineages of the Arabian breed display complex ancestry. Each cluster in a given analysis panel is represented by a separate color.

The plotted samples represent Arabian breed subgroups as well as Turkemen, Icelandic and Thoroughbred breeds. Sample order is the same in each panel. The purple bar and asterisk mark the cluster of multi-origin samples showing shared ancestry with Thoroughbred samples.

We used RFMix 26 to explore the genetic relationship among Arabian horses used for flat racing competitions and the Thoroughbred breed analysis data set: , SNP genotypes from samples.

In some registered flat-course racing Arabian horses, near full length chromosomes appear to originate from Thoroughbreds Fig. We included data from Icelandic horses as a negative control, as any contact between Icelandic and Arabian horses in the last years would be extremely unlikely given the recorded history of these two breeds. We also included samples of Turkemen horses from Iran including individuals of the Akhal-Teke breed, a descendant of the extinct Turkoman horse as a reference group, given previous studies that have suggested that the Arabian is closely related to these populations 27 , and the possibility of admixture, given the overlapping historical geographic ranges of these two populations.

The autosomal admixture patterns illustrated by the RFMix analysis Fig. Admixture analysis indicates presence of Thoroughbred ancestry in Arabian horses used for flat course racing. Each row is a haplotype, with individuals pairs of haplotypes separated by horizontal white lines. Given that RFMix analysis identified recent admixture of Thoroughbred genomic regions into present-day Arabian horse genomes, we explored the sire-dam direction of interbreeding by examining the Y chromosome haplotypes of selected male Arabian horses used for show or racing competitions, using recently published methods The 29 non-racing Arabian horses all carried one of three Y haplogroups previously associated with Arabian horses Fig.

The two most common haplogroups, Ao-1 and Ao-2, were previously documented as ancestral to modern Arabian horses The Ta haplogroup is genetically more similar to haplogroups of modern Thoroughbreds, but is only observed in Arabians Notably, only two of the 10 male race-use Arabian horses examined carried any of these three Arabian Y haplogroups Ao-1, Ao-2 and Ta.

Therefore, these five horses may carry Y chromosomes derived from ancestors common to both racing Arabians and the Thoroughbred breed However, the remaining three racing Arabian horses carried the Tb-dW1 haplogroup, also known as the Whalebone haplotype. Tb-dW1 is almost fixed in Thoroughbred horses and has not been reported previously in modern Arabians. Y chromosome haplotyping supports use of Thoroughbred sire lines in the Racing Arabian subgroup.

A Reduced haplotype network map of the male-specific region of the Y-chromosome according to 21 with SNPs genotyped in this study in red. Detected haplotypes are colored, and haplotypes in white circles were not detected in the 39 Arabian males genotyped. Haplotypes in green were previously detected in Arabian horses in other studies 21 , B Y haplotype frequencies in racing versus non-racing Arabian horses shown in absolute numbers. Arabian horses possess unique physiological traits that result from selection for the diverse activities humans raise and train them for, as well as the challenging natural environments in which these horses thrive.

We examined genetic divergence as evidence of putative selective sweeps among groups selectively bred for flat-course racing, as well as across subpopulations from diverse geographic and cultural origins. Notably, GPX1 encodes the glutathione peroxidase enzyme, a selenoprotein that mitigates oxidative damage and is frequently associated with exercise in both human and equine athletes 30 , No polymorphism in coding sequences within this region was found relative to the reference genome assembly from a Thoroughbred horse among the eight Arabian genome sequences examined for this work.

Selection scan statistics highlight a candidate region on ECA 16 containing GPX1 , a gene important for protection from exercise-induced oxidative damage across Arabian lineages. Colored asterisks indicate which test statistics had peaks exceeding the indicated threshold within the region of interest.

The Straight Egyptian subgroup, prized primarily for its beauty and value in the show ring, possesses six putative sweep signals capturing the region chr,,,, Fig. One strongly supported peak window, chr,,,,, overlaps just three annotated genes. Of particular interest among these, TMEM encodes a transmembrane protein with a putative function as a zinc transporter Human GWA studies correlated markers at TMEM with the width of the face between the eyes, and the relative height of the eyes on the face Selection scan statistics reveal a putative selective sweep unique to the Straight Egyptian subgroup on ECA The vertical gray region indicates the genomic region encompassing all 6 peaks observed for the Straight Egyptian group.

The Arabian horse presents a paradox within equestrian culture. To those who admire the breed, the gracefully shaped head with dished forehead and wide-set eyes are the iconic representation of the Arabian horse. Furthermore, virtually every horse fancier can recite the story of the influence of Arabian stallions in founding the modern Thoroughbred breed 20 , 35 , To its detractors, the Arabian represents an overly inbred horse breed with a high incidence of inherited autosomal recessive diseases Here we tested a large collection of Arabian horses from many countries and breeding lines using a combination of whole-genome sequencing and the k equine single nucleotide polymorphism SNP array.

We analyzed this dataset with comparable data in the public domain from 18 other breeds. Our results challenge long-held assumptions about the Arabian horse. Despite having been dispersed widely across the globe by humans, the breed as a whole maintains a unique genetic identity observable by geometric segregation in a very broad swath of PC space Fig. This finding agrees with the written histories of these groups, characterized by closely controlled breeding of these lineages over the past years 6.

A similar sub-breed structure has been described in the American Quarter Horse, a registry notable for its functional division into several subgroups that also cluster separately in PC space This subgroup may be subject to relatively intense selection for the specific conformation types preferred in the show ring. Despite relatively diverse pedigrees, the high inbreeding values were also observed within individual horses of the multi-origin category.

This may reflect population bottlenecks that occurred during exportation of these horses from the Middle East to individual stud farms in the USA and Europe, followed by modern breeding practices that are often driven by a popular sire effect.

Inbreeding within some lines of Arabians has increased the occurrence of a number of recessive inherited diseases 38 , 39 , Similarly, within the American Quarter horse subgroups inbreeding values vary considerably, and the individual subgroups display different associations with inherited diseases We identified registered Arabian horses resident in the Middle East that clustered with the Arabian breed, but that carried expanded genetic and phenotypic diversity.

Increased diversity in these subgroups is consistent with a Middle Eastern origin for the modern Arabian horse. Unfortunately, documentable ancestral populations may no longer exist for the Arabian, as for most domesticated horses, and populations of unregistered horses are difficult to identify and sample in this region. Our results confirm and extend findings reported earlier by two groups.

Although they used only 15 polymorphic microsatellites for their study, they identified higher genetic diversity in Arabian horses from the Middle East region than in horses from other regions. Furthermore, they showed evidence for complex ancestry in many Middle Eastern populations, but not in the Straight Egyptian horses. Almarzook and colleagues used the same k SNP array that we used in our study, but they tested only 48 horses drawn from Syria and the USA Even with this small sample size, they observed high levels of genetic diversity in the Syrian horses.

They also failed to show correlation between genetic ancestry defined using SNP array data and the traditional definition of maternal strains maintained by Arabian horse breeders, including those in Syria.

Neither study examined the diversity of the Arabian horse within the context of a global sampling of horse breeds. However, considered with the findings we present here, these three reports make a strong case for the existence of robust, genetically diverse populations of Arabian horses in the Middle East today.

Thus, although the global population of Arabian horses is diverse, loss of diversity within some subgroups like the Straight Egyptian may be reaching levels sufficient to impact animal health Indeed at least three recessive genetic diseases segregate within the Arabian horse, and are already of particular concern within some subgroups 9 , This finding highlights the need for use of genomic tools to manage inbreeding within these populations as pedigree-based calculations may not accurately measure loss of diversity due to historic events Likewise, identity-by-state guided breeding decisions could assist in maintaining rare alleles and heterozygosity in endangered populations, both in the Middle East and abroad.

Historical evidence suggests that the Arabian was selectively bred for its distinctive conformation, characterized by a dished facial profile, graceful upright neck, and high tail carriage, over the last 3, years 2. Natural selection imposed by the hot and arid environments under which the Arabian horse was traditionally reared may have also altered regions of the genome, thus conferring a cost to relative fitness. A putative sweep on ECA16 was common to all Arabian subgroups, but not found in control breeds tested here Fig.

Dietary supplementation with selenium is suggested as a method to increase activity of the GPX1 enzyme glutathione peroxidase , a candidate gene within this ECA 16 sweep. This increase in activity may reduce oxidative damage to muscle and blood tissues resulting from exercise, thereby improving performance Many studies have examined changes in blood glutathione peroxidase activity pre- and post- training, and resting blood activity of this enzyme is higher in race-trained Thoroughbreds than in other athletic horses However, glutathione peroxidase expression or basal activity has not yet been compared across breeds, nor specifically in athletic types vs.

Therefore, conserved regulatory motifs and additional sequencing across breeds with diverse athletic ability may be logical targets of further investigation across GPX1 , as well as other genes within this candidate sweep region. We also observed evidence of selective breeding for specialized competitions such as racing and show across Arabian subgroups Fig. Although future work is needed to better determine any phenotypes attributable to this sweep, the Straight Egyptian does possess a particularly notable expression of the highly prized concave Arabian facial profile.

Thus, the Arabian horse may be an advantageous model for identification of genes contributing to skull morphology, as has been previously demonstrated in the dog Finally, we identified undocumented relationships between the Thoroughbred breed and the modern Arabian that are contrary to breed registry regulations and dispute long-held myths.

This disagreement may stem from a simple confusion surrounding the naming of these horses. In contrast, we detected evidence of modern outcrossing of registered racing-type Arabians to the Thoroughbred, a practice that is prohibited by Arabian horse registries Figs.

Taken together, our observations lead us to hypothesize that only a small proportion of total genetic diversity left the Middle East when Arabian horses were imported to Europe and the USA over the past years.

The residual genomic and phenotypic diversity within the Arabian horse breed in the Middle East is indicative of a high long-term effective population size, and also reflects the overall robust genetic health of this population. The genetic history of the Arabian thus holds greater interest and fascination than the myths that have surrounded this charismatic breed of horse for over years. The application of modern breeding techniques, such as artificial insemination, is producing an international pedigree of modern Arabian horses marked by genetic homogenization, and in some cases, severe inbreeding and pedigree errors.

This emphasizes the critical need for more detailed studies of genomic diversity in native Arabian horses in order to enable conservation efforts and manage inbreeding in at-risk subgroups. The Middle Eastern subgroups examined here Iranian, Bahraini, Tunisian, Syrian and others may represent refugia of genetic diversity crucial to the future of the Arabian horse.

Sample counts per breed and per lineage group are reported in Supplemental Table S3. The geographical location of the collected samples is shown in Supplemental Fig. Blood and hair sampling from each horse was completed with the consent of the horse owner under all appropriate institutional guidelines and was approved by the Animal Care and Use Committees at Cornell University and and the University of Florida and Genomic DNA was extracted using conventional methods. Although most modern Arabian horse registries fall under the umbrella of the World Arabian Horse Organization WAHO and are registerable across the various national breed organizations, some Arabian horse populations, like those in Iran Persian Asil horse , have remained relatively geographically and genetically distinct.

The Persian Arabian studbook extends back only to , but it is likely that the lineages may be more ancient. In Iran, Mary Gharagozlou worked tirelessly during the second half of the 20 th century to document the pedigrees of pure-bred Persian Arabian horses, including lineages tested in this study We sought out horses that were described by their ownership history and pedigree as representing examples of diverse locally bred lines.

We grouped Arabian horse populations based on the origin recorded for founders identified in pedigrees maintained by the studbook. These horses are often associated with the Egyptian stud farm of Abbas Pasha or the Egyptian Royal Agricultural Society breeding programs 2.

Outside of Egypt, records on these horses are currently maintained by the Pyramid Society organization, and in North America the Al Khamsa Arabian registry.

Poland has a long history of selective breeding of Arabian horses 6 , 8. Arabian lineages were first imported to Poland in and their numbers supplemented over the years by new horses imported directly from the Middle East beginning in Violence during World War I and II nearly destroyed all Polish-Arabian horses and the modern lines maintained in the Polish breeding program were started between and We also identified groups of samples with origins in Bahrain, Iran, Poland, Saudi Arabia, Syria, and Tunisia, as well as a collection of 17 Thoroughbred and two Standardbred samples as reference outgroups.

Genotyping was conducted at GeneSeek Inc. Arabians are prone to several genetic disorders, ranging in seriousness from treatable to fatal. They include:.

In terms of behavior, Arabians are generally very sociable with people. Arabian horses need standard equine grooming to keep their coat and skin healthy.

Regular brushing, especially after exercise, will distribute sweat and oils. And using a detangler can help keep their mane and tail smooth. Arabians have played prominent roles in history, carrying important people in war, winning races, and garnering starring roles in movies and books.

A few examples include:. Arabian horses can be loving, loyal, and responsive companions. But they are hot-blooded and highly intelligent horses that need someone with equine experience to train them. Some older and well-trained Arabians—as well as Arabian crossbreeds—might work for a person with limited horse knowledge, though Arabians do typically remain active well into their golden years. Arabians tend to be more people-oriented than many other horse breeds, and they enjoy the company of their human families.

They're generally a healthy and hardy breed, and they adapt well to a range of environments. Because Arabians are a popular breed, they are fairly easy to find at reputable horse rescues or breeders. And if possible, have your own vet check out the horse before you decide to bring it home. Also, spend time with the horse, and have the organization show you how it has been trained. If you ever feel the organization is not being transparent or rushing you through this process, you might consider looking elsewhere for your horse.

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