Horse Coat Color Research Articles

Study of <i>ASIP</i> and <i>MC1R</i> gene polymorphism horses of the kabardian breed

The coat color of horses is of considerable interest due to its aesthetic appeal and significance in breed identification. Understanding the genetic mechanisms underlying coat color variation is important for horse breeders and geneticists. The purpose of the study is to study the influence of polymorphism of the MC1R and ASIP genes on the coat color of Kabardian horses, a unique domestic breed. The proposal is not agreed upon, the idea is not clear. Why was the research done? Based on the results of genotyping 127 horses of the Kabardian breed using the MC1R and ASIP genes, the frequencies of various alleles and genotypes on which the color of the animals depends were determined. Statistical analysis was carried out to determine the relationship between them. Kabardian horses are characterized by a wide range of colors, including karak, black, bay, dark bay and gray. The majority of the horses studied (96.9 %) were found to have a dominant allele E of the MC1R gene, associated with the synthesis of eumelanin and darker coat color. The frequency of the A/A genotype of the ASIP gene increased as the coat color lightened: black – 0.0 %, karak – 9.5 %, dark bay – 56.6 %, bay – 84.8 %. The frequency of the mutant allele a was 0.280. In general, it contributed to the formation of black coat color in Kabardian horses. The results of the study provide insight into the relationship of the MC1R and ASIP genes with the formation of coat colors in Kabardian horses. These results have practical implications for horse breeders when selecting individuals for crossbreeding and contribute to the understanding of the genetic mechanisms underlying variation in coat color within horse populations.

Three HPS5 mutations associated with depigmentation in diverse horse breeds

Depigmentation is a common phenotype in Equus caballus (horse); over 50 identified variants cause white spotting on the skin and coat. HPS5 may influence melanocyte proliferation and mutations in this gene cause depigmentation in humans, mice, and zebrafish. Here we report three equine HPS5 mutations, found in most major breed groups and associated with white spotting. We used a standardized method to quantitatively grade depigmentation, creating a White Score for each horse. We identified associations to each of three variants in HPS5 by comparing the average white score for carriers to that of 41 control horses possessing none of the studied variants. We estimated the functional impact of each mutation using SIFT, GenScan, I-TASSER and cross-species conservation. The first mutation, S1013C termed Eden White 1 (EDXW1), is a missense mutation found to increase average depigmentation by 5.56 points (p = 6.47E-6, n = 70, t-test). Eden White 2 (EDXW2), a missense mutation L560F, increased depigmentation by 9.5 points for individuals with one copy of the variant, but we were unable to phenotype homozygotes (p = 5.55E-16, n = 47, t-test). Eden White 3 (EDXW3), a putative donor splice site mutation at exon 4 + 4, increased white by 5.59 points on average (p = 9.56E-6, n = 101). EDXW1 and EDXW3 are epistatically influenced by MC1R, the gene that controls black vs red coat color in horses. Individuals possessing the dominant E allele produce black pigment, and this allele was associated with higher levels of depigmentation than individuals with the recessive chestnut genotype (e/e) (p = 1.50E-5, p = 1.26E-5 respectively). We tested for epistatic interactions between EDXW1 and Dominant White 20 and found that horses with one copy of each allele had increased average white spotting by 8 points with respect to EDXW1/n or W20/n horses. Compound heterozygotes were significantly more white than horses with one copy of either mutation (p = 7.33E-5), but interactions between other white spotting alleles and EDXW alleles remain to be tested. We propose the convention Eden White (EDXW) for HPS5 mutations in the domestic horse.

The system of mono-and polylexeme adjectives describing horse head markings in the Sakha language

This article presents a system of adjectives, describing horse head markings in the Sakha language, based on structural and lexical-semantic analysis. The relevance of the study is conditioned by the fact that so far, the names of horse head markings in the Sakha language have not been systematized. The study uses 25 names extracted from lexicographic sources. To clarify the etymology of the names, we involved lexical parallels from the Mongolian, Buryat, Evenki and Even languages. E. A. Kosykh’s theory served as an idea for developing the system. The study showed that 7 analyzed color-designations consist of one lexeme and belong to monolexeme names, which are used separately from horse coat сolors. We have established that polylexemic color-definitions, which are represented by 18 names, are formed by adding two components where one of the components is a clarifying component and the other is a supporting one. As the analysis has shown, the clarifying component is expressed by the bases of nouns denoting various phenomena: objects and animals. By developing the system of names for horse head markings we get a broader and more complete picture of color designations describing horse colors in the Sakha language.

Effects of dietary camelina, flaxseed, and canola oil supplementation on transepidermal water loss, skin and coat health parameters, and plasma prostaglandin E2, glycosaminoglycan, and nitric oxide concentrations in healthy adult horses

Abstract Camelina oil is derived from a low-input, high-yield crop and, in comparison to many other dietary fat sources currently used in equine diets, provides a greater amount of α-linolenic acid [ALA; (n-3)], than linoleic acid [LA; (n-6)]. However, no research exists assessing the effects of feeding camelina oil to horses in contrast to other commonly used oils. The objective of this study was to compare the effect of supplementing camelina oil to that of flaxseed and canola oil supplementation, on outcomes related to skin and coat health in horses. Thirty adult horses [23 mares, 7 geldings; 14.9 years ± 5.3 years; 544 ± 66 kg body weight (BW) (mean ± SD)] underwent a 4-week wash-in period consuming hay and sunflower oil. Following the wash-in period, horses were blocked by location, age, and BW, and assigned to one of three treatment oils for 16 weeks (370 mg oil/kg BW): camelina (CAM), canola (OLA), or flaxseed (FLX) oil. Blood samples were collected and plasma prostaglandin E2 (PGE2; ELISA), nitric oxide (NO; Griess Reaction), and glycosaminoglycan (GAG; DMMB) concentrations were measured on weeks 0 (n = 30), 14 (n = 24), and 16 (n = 30). On weeks 0, 2, 4, 8, and 16, transepidermal water loss (TEWL) was measured pre- and post-acetone application using a VapoMeter (n = 26), and a 5-point-Likert scale was used to assess skin and coat characteristics on the side and rump of the horses (n = 30). All data were analyzed with repeated measures ANOVA using PROC GLIMMIX in SAS. Independent of treatment, coat color, and quality increased from baseline. There were no differences in the outcomes assessed between the horses supplemented camelina oil and those supplemented canola or flaxseed oil. These results suggest that independent of treatment, all oil supplements improved coat color and quality in horses. This provides indication that camelina oil is comparable to existing plant-based oil supplements in supporting skin and coat health and inflammation in horses.

Genes affecting coat colour and the resulting variation in horses (Equus caballus) – A Review

Horse colour is important. People chose horses for their colour pattern diversity, according to archaeological investigations and biological evidence. Horses were generally dark coloured before domestication, according to molecular testing. After domestication, the genes for white patterns and dilutions appeared. The appearance of their horses, as well as their competence and willingness to work, must have been important to early people. In many cases, the genes that impact coat colour patterns in one species also influence coat colour patterns in another. In horses, humans, cattle, dogs, and other species, the MC1R gene encodes the alleles for red and black of the Extension locus. White spotting is caused by mutations in the KIT gene in horses (tobiano, roan, sabino, dominant white), mice, and humans. Because of its similarity to a white hair gene seen in humans with Hirschprung's illness, the gene for overo in horses was discovered. The genes that impact coat colour patterns in one species generally play a similar role in another, according to molecular studies. It came as no surprise. Earlier geneticists claimed that coat colours in horses were caused by the action of genes similar to those observed in other species based solely on phenotype. This is a crucial lesson for genetic studies: we can apply what we have learned from other species to our own. All in all, the study of coat colour variations in the horse is a study of the horse's nature.

Melanocortin‐1 receptor influence in equine opioid sensitivity

SummaryIndividual variation in opioid sensitivity can have a profound impact on the safety and efficacy of equine veterinary treatments, with the ability to adequately manage equine pain in a clinical setting currently limited. This review aims to explore the overlap between biological mechanisms associated with opioid metabolism and those mechanisms associated with coat colour in horses as has been documented in humans, with particular focus on the melanocortin‐1 receptor (MC1R) gene. In the future, the use of the MC1R coat colour genotype could help to indicate variable opioid sensitivities thereby greatly improving the use of opioids in clinical settings. The MC1R gene has a well‐established role in melanogenesis and pigment switching, but involvement in the pain‐modulating periaqueductal grey (PAG) descending pathway and in immune responses, both of which contain opioid receptors, has also been suggested in humans. However, this relationship between opioid metabolism and the connection to the three known MC1R variants (EE, Ee and Eea) in horses is yet to be explored.

Functional Characteristic of the Designation of the Equine Coat Color in Epic Texts in a Comparative Aspect

The article is dedicated to the functions of the designation of the horse colors in the epic texts of related Turkic peoples – the Yakuts, the Khakass and the Altaians. The relevance of the study is due to the fact that until now in the Yakut language the lexical layer denoting the names of the horse colors has not become the subject of a comprehensive study. The purpose of the article is to study the semantics of designation of equine coat colors in the epic texts of mentioned Turkic peoples and to identify the commonality and specificity of its functioning. It was found that in the texts of the northern olonkho there are 10 color designations of horse colors, in the Khakass epic – 10, in the Altai – 7. It was revealed the general that designations of the horse color in the literal sense serve for a reliable and colorful description of the appearance of an epic horse; in the Altai and Yakut epos, depending on the context, the sacred meaning associated with the mentality of each of the peoples is realized. In the Yakut epic, horses of a certain color turn into different objects, and in the Altai - into horses of a different color. In the texts of the northern olonkho, there are no designations of dun, roan colors, and this is due to the fact that horses of these colors were rare in the places of residence of the northern Yakuts; in the Khakass epos, many designations of equine coat colors indicate piebald horse color.

Genetic Background of the Polish Primitive Horse (Konik) Coat Color Variation-New Insight into Dun Dilution Phenotypic Effect.

Only the blue dun coat color, produced by the action of the dun allele on the background of a black base coat, is officially permitted in the Polish primitive horse (PPH, Konik) breed, yet the population is not visually homogenous and various coat color shades occur. Herein, the molecular background of PPH coat color was studied based on genotyping of known causative variants in equine coat color-related genes (ASIP, MC1R, TBX3, SLC36A1, SLC45A2, PMEL17, and RALY). Additionally, screening for the new polymorphisms was conducted for the ASIP gene coding sequence and the TBX3 1.6-kb insert (associated with the dun dilution). We did not observe the champagne, silver, or cream color dilution variants in the PPH breed. A significant association (P < 0.01) was recorded for the genotype in TBX3 gene 1.6 kb in/del and the degree of dun coat dilution, demonstrating that the dominant action of the dun mutation is not fully penetrant. In addition to the effect of the 1.6 kb in/del zygosity, variants within the TBX3 insert were significantly associated with PPH coat color variability (P < 0.01), suggesting the presence of an additional allele at this locus. Finally, we identified a high frequency (35%) of genetically bay dun-colored PPH individuals that are officially recorded as blue (black base coat) duns. We propose that the difficulty in distinguishing these 2 phenotypes visually is due to an independent locus upstream of the ASIP gene, which was recently described as darkening the typical bay pigmentation shade.

GWAS Identifies a Region Containing the SALL1 Gene in Variation of Pigmentation Intensity Within the Chestnut Coat Color of Horses.

Chestnut coat color in horses is determined by a missense mutation within the MC1R gene. However, the intensity of the chestnut color can vary widely within individuals possessing this genotype. Here, we investigated this variation using standardized photographs of 96 horses. Each horse was ranked lightest to darkest within the cohort for phenotype by 3 blinded observers. A genome-wide association study utilizing the relative shade ranking as the phenotype and using 268 487 single-nucleotide polymorphisms (SNPs) genotyped using the Affymetrix Equine 670k array identified a single significantly associated region on chromosome 3 (P = 2.934 × 10-8). Analysis of whole-genome sequences for horses spanning the diverse range of chestnut color identified candidate SNPs within the coding sequence of the only gene in the region: SALL1. The function of SALL1 is largely unknown, though it is predicted to interact with the Hermansky-Pudlak Syndrome type 1 (HPS1) protein, which causes partial albinism in humans. However, with only one study suggesting a circumstantial influence of the SALL1 protein on pigmentation, additional work is needed to confirm this new coat color locus in larger populations and investigate the function of this protein for impacts on equine health.

Историческое и лексико-семантическое развитие цветообозначения al ‘алый, розовый’ в тюркских языках

Introduction. The article examines the color term al ‘pink; scarlet’ in Turkic languages. Goals. The study aims at considering the lexeme in comparative historical and lexical-semantic perspectives. This involves a number of objectives, such as to review and analyze hypotheses on etymology of the word, identify the functioning of the lexeme in ancient and modern languages, determine characteristics of use of the word’s meanings in certain Turkic languages, delineate common Turkic and specific (belonging to a separate subgroup) development trends of the lexeme al. Materials and Methods. To facilitate the latter, an extensive theoretical and source base on Turkic languages is employed: when it comes to origins of the word, special attention is paid to fundamental scientific works on Turkic and Altai etymologies; ancient Turkic, medieval written monuments, lexicographic works on particular Turkic languages are examined to reveal semantic features of the word in ancient and modern languages. In general, the work proves topical due to the absence of any comprehensive study dealing with etymology, development and functioning of the token in Turkic languages. Results. The study reveals that the al lexeme is essentially ancient: scholars have restored its Pre-Turkic (*Āl) and Pre-Altaic (*ŋiōle) forms, with its Nostratic origin identified. The word is frequently traced in written sources of the Turks from earliest monuments. The token al is integral to most Turkic languages, except for the Chuvash, Altai, Tuva, Karachay-Balkar, and Karakalpak ones. In Yakut and Khakass, the lexeme ālaj is perceived as a loanword. Thus, the gloss al was widely used mainly in Western Turkic languages. In ancient and modern Turkic languages, the word al has meanings as follows: ‘scarlet, pink, ruddy’, ‘orange’, ‘brown’, ‘red, bay (horse coat color)’, ‘young’, ‘yellow’, ‘noble’, ‘magical’, ‘bright, motley’, and some substantives ― ‘seal, credential issued by Khans’, ‘rouge’, ‘woman’s headwear’. Conclusions. The ancient Turkic colour term al is (was) not universally distributed in all Turkic languages. The wide (though uneven) use of the word and further development of its semantics occurs in the Kipchak and Oghuz languages where the gloss al has a number of additional connotative and metaphorical meanings.

An Independent Locus Upstream of ASIP Controls Variation in the Shade of the Bay Coat Colour in Horses.

Novel coat colour phenotypes often emerge during domestication, and there is strong evidence of genetic selection for the two main genes that control base coat colour in horses—ASIP and MC1R. These genes direct the type of pigment produced, red pheomelanin (MC1R) or black eumelanin (ASIP), as well as the relative concentration and the temporal–spatial distribution of melanin pigment deposits in the skin and hair coat. Here, we describe a genome-wide association study (GWAS) to identify novel genic regions involved in the determination of the shade of bay. In total, 126 horses from five different breeds were ranked according to the extent of the distribution of eumelanin: spanning variation in phenotype from black colour restricted only to the extremities to the presence of some black pigment across nearly all the body surface. We identified a single region associated with the shade of bay ranking spanning approximately 0.5 MB on ECA22, just upstream of the ASIP gene (p = 9.76 × 10−15). This candidate region encompasses the distal 5′ end of the ASIP transcript (as predicted from other species) as well as the RALY gene. Both loci are viable candidates based on the presence of similar alleles in other species. These results contribute to the growing understanding of coat colour genetics in the horse and to the mapping of genetic determinants of pigmentation on a molecular level. Given pleiotropic phenotypes in behaviour and obesity for ASIP alleles, especially those in the 5′ regulatory region, improved understanding of this new Shade allele may have implications for health management in the horse.

Taygalı Avcıları, Balıkçıları ve Toplayıcılarının Destanlarında Süt Beyaz Atlar

One of the most interesting of the numerous riddles that Siberian native cultures present for researchers is according to the author, the way in which Taiga hunters, fisherman and wild plant gatherers created their magnificent epics, describing warriors of the steppe, who lived in golden palaces and owned great numbers of people and countless herds of sheep and cattle. On the basis of field data and analysis of dozens of epic narratives of the Taiga Shor people, the author describes the types of horses, coats and their lay classifications. He finds that the Shor language provides as many terms for horse coat color designation as the Teleuts of Bachat and other descendants of the steppe nomadic cattle herders might give. Pondering upon the considerable contradictions between the epic and ethnographic worldviews, the author highlights the importance of the Shor horse breeding and cattle raising terminology research, underscoring a thousand year gap between the epic reality and the ethnographic period when these epic narratives were put down in writing. Keywords: Epic, hero, colors of horses, Turk, Shor, Teleut, Siberia, Altay.

A Genome-Wide Association Analysis in Noriker Horses Identifies a SNP Associated With Roan Coat Color

The roan coat color in horses is characterized by dispersed white hair and dark points. This phenotype segregates in a broad range of horse breeds, while the underlying genetic background is still unknown. Previous studies mapped the roan locus to the KIT gene on equine chromosome 3 (ECA3). However, this association could not be validated across different horse breeds. Performing a genome-wide association analysis (GWAS) in Noriker horses, we identified a single nucleotide polymorphism (SNP) (ECA3:g.79,543.439 A > G) in the intron 17 of the KIT gene. The G -allele of the top associated SNP was present in other roan horses, namely Quarter Horse, Murgese, Slovenian, and Belgian draught horse, while it was absent in a panel of 15 breeds, including 657 non-roan horses. In further 379 gray Lipizzan horses, eight animals exhibited a heterozygous genotype (A/G). Comparative whole-genome sequence analysis of the KIT region revealed two deletions in the downstream region (ECA3:79,533,217_79,533,224delTCGTCTTC; ECA3:79,533,282_79,533,285delTTCT) and a 3 bp deletion combined with 17 bp insertion in intron 20 of KIT (ECA3:79,588,128_79,588,130delinsTTATCTCTATAGTAGTT). Within the Noriker sample, these loci were in complete linkage disequilibrium (LD) with the identified top SNP. Based upon pedigree information and historical records, we were able to trace back the genetic origin of roan coat color to a baroque gene pool. Furthermore, our data suggest allelic heterogeneity and the existence of additional roan alleles in ponies and breeds related to the English Thoroughbred. In order to study the roan phenotype segregating in those breeds, further association and verification studies are required.

Inconsistencies in horse coat color registration: A case study.

ABSTRACTGrullo is a dun dilution on a black coat that is common in the Campolina horse: an autochthonous Brazilian breed. The aims of this case study were to evaluate inconsistencies in grullo coat color registration and to explain their possible causes. A total of 3,270 grullo Campolina horses were evaluated. To confirm the genetic possibility of having grullo animals, the coat color genotypes of parents were inferred by phenotype and compared with those of progeny. A total of 242 horses that were registered as grullos could not have this coat based on their parents’ information. Possible explanations for incorrect registration are errors of paternity and in coat color identification. We suggest maintaining obligatory paternity testing and enhancing training in coat color identification.

Horse vision and obstacle visibility in horseracing

Visual information is key to how many animals interact with their environment, and much research has investigated how animals respond to colour and brightness information in the natural world. Understanding the visibility of features in anthropogenic environments, and how animals respond to these, is also important, not least for the welfare and safety of animals and the humans they co-exist with, but has received comparatively less attention. One area where this is particularly pertinent is animal sports such as horseracing. Here there is a need to understand how horses see and respond to obstacles, predominantly fences and hurdles, as this has implications for horse and rider safety, however obstacle appearance is currently designed to human perception. Using models of horse colour and luminance (perceived lightness) vision, we analysed the contrast of traditional orange markers currently used on fences from 11 UK racecourses, and compared this to potential alternative colours, while also investigating the effect of light and weather conditions on contrast. We found that for horses, orange has poor visibility and contrast against most surroundings. In comparison, yellow, blue, and white are more conspicuous, with the degree of relative contrast varying with vegetation or background type. Results were mostly consistent under different weather conditions and time of day, except for comparisons with the foreground turf in shade. We then tested the jump responses of racehorses to fences with orange, fluorescent yellow, bright blue, or white takeoff boards and midrails. Fence colour influenced both the angle of the jump and the distances jumped. Bright blue produced a larger angle of takeoff, and jumps over fluorescent yellow fences had shorter landing distances compared to orange, with bright blue fences driving a similar but non-significant trend. White was the only colour that influenced takeoff distances, with horses jumping over white fences having a larger takeoff distance. Overall, our results show that current obstacle coloration does not maximise contrast for horse vision, and that alternative colours may improve visibility and alter behavioural responses, with the ultimate goal of improving safety and welfare.

The Genetic Basis of Piebald Coat Colour in Hucul Horses in the Context of White Markings and Crypto-Tobiano as a Breeding Problem in Poland

Abstract The aim of the study was to analyse the genetic basis of piebald coat colour in Hucul horses and to verify their coat colour in breeding records. Tests were performed with DNA purified from the whole blood samples of 242 Hucul horses with different coat colour patterns. DNA was analysed to identify an inversion in ECA3 (PCR). The results confirmed that the inversion on ECA3 is a direct factor determining piebald (tobiano) colour in the analysed Hucul horses. No inversion was observed in any of the solid coloured horses, but it was present in all the piebald ones. It was also identified in 18% (11 of 61) of the horses from the group of horses qualified in the passport as solid coloured with white markings. In fact, these horses had the tobiano gene that is phenotypically identifiable as crypto-tobiano, which may give the false impression of having white markings and lead to error when describing a horse. This is an important issue, in particular with regard to the breed standard, which eliminates Hucul horses with white markings from breeding.

Estimation of genetic and non-genetic effects influencing coat colour in black horses

The aims of this study are the quantitative characterisation of the coat colour in the black variety of the Old Kladruber Horse breed, the estimation of the coat colour genetic parameters, and the determination of the factors that influence coat colour intensity. A total of 252 horses aged 1–24 years were included in the study. The colour parameters were taken using a Konica Minolta spectrophotometer CM-2500d at four different body parts during the summer and winter seasons, resulting in 1748 phenotypic records. The possible effects of sex, season, housing system, age and body part on the spectrophotometric parameters were analysed. The results confirmed that the intensity of the black coat colour can be influenced by a number of factors (sex, season, housing system, and age). The mares showed more red and yellow colour compared to the stallions. In the winter season, the horses had a lighter colour with a lower proportion of reddish-brown hairs. Horses kept outdoors, especially in the summer months, had a lighter colour with a higher proportion of red and yellow. Although the age was statistically significant, no specific trend was observed. The differences in colour found between body parts (neck, shoulder, belly, and croup) are in line with current knowledge – reddish fading in the blacks primarily occurs in the belly region. The estimated heritability values suggest possible multifactorial inheritance, especially with regards to the reddish tinge in hairs (h&lt;sup&gt;2&lt;/sup&gt; = 0.20 to 0.29 according to body part).

THE WORD ‘BROWN’ AS A HORSE COLOUR NAME: SEMANTICS AND WAYS OF TRANSLATION

The article is devoted to the problem of translation of the word brown as a member of the lexico-semantic group horse colour. This study aims at comprehensive description of the semantics of the said word, supported with references to definitions from specialized literature on horse genetics. The article also describes the possible variants of translation of the word brown into Russian, since there is no single equivalent. To achieve this goal, the word in question is analyzed with the use of an English and parallel Russian-English corpora. The degree of equivalence of the word brown and its Russian counterparts is established through comparison of word definitions from different sources. This study is carried out with the use of the following methods: the method of continuous sampling for data collection from English and Russian corpora, the comparative method for establishing the degree of equivalence among horse colour names, the method of analysis for processing the results of the comparison, the method of synthesis for comprehensive description of the ways of translation of the word brown. The materials for this study include works on horse colour genetics, horse colour reference charts and encyclopedias. The examples are provided by the Russian National Corpus (parallel subcorpus) and the iWeb Corpus of the English language. Some examples have been processed without the use of a corpus, which is reflected in the inclusion of works of fiction to the reference list. This study adds new information to the available data on the word brown as a horse colour name. The methodological novelty of this work is the use of the corpora to analyze a specific horse colour name and its representation in fiction.

Matching Elements of the “Horse Colour” Lexico-semantic Group in the Russian Literature

Matching Elements of the “Horse Colour” Lexico-semantic Group in the Russian Literature

Morphological and genetic diversity of Pura Raza Español horse with regard to the coat colour.

Gene mutations influencing melanocytes also impact on physiological and behavioural functions. In this study, we investigated their association with four different coat colours in the Pura Raza Español (PRE) horse using morphological traits and molecular datasets. Four different subpopulations were identified according to individual coat colour: grey, bay, chestnut and black. Coat colour significantly associated with morphological measurements. Observed and expected heterozygosity values were low in grey compared with the other three subpopulations, suggesting the presence of unique ancestral alleles probably arisen by genetic drift and selection mechanism effects. Nei's distance demonstrated a clear division among subpopulations, the grey being the most divergent group. Gene flow estimates were similar, showing the lowest values in grey. Divergence times among subpopulations assessed with the average square distance suggested that grey was the original PRE population which diverged from bay, chestnut and black. Our results also demonstrated a clear morphological differentiation according to coat colour. The close genetic structure of bay and chestnut PRE subpopulations and the clear differences in most morphological traits of grey and chestnut PRE mares would suggest the pleiotropic effect of genomic regions determining coat colour in horses. However, further analysis including genomic information would be necessary to elucidate the mechanisms involved.