Genomics in horses involves the study and analysis of the horse genome to understand genetic variations and their implications for equine health, performance, and breeding. This field encompasses the identification and mapping of genes associated with specific traits, diseases, and conditions in horses. Techniques such as whole-genome sequencing and genome-wide association studies (GWAS) are employed to explore genetic diversity and inheritance patterns among different horse breeds. Genomics provides insights into hereditary disorders, informs selective breeding practices, and aids in the development of personalized veterinary care. This page compiles peer-reviewed research studies and scholarly articles that explore the applications, methodologies, and findings of genomic research in equine science.
Na W, Hong M, Yeom M, Kim S, Kim JK, Song D.We analyzed the complete genome sequence containing the 3' and 5' noncoding regions (NCRs) of the Korean H3N8 equine influenza virus (EIV), which will provide a better understanding of the pathogenesis, transmission, and evolution of EIV.
Begg AP, Todhunter K, Donahoe SL, Krockenberger M, Slapeta J.A case of amoebic placentitis in a mare from eastern Australia was diagnosed postpartum by histopathological examination of the placenta. The identity of the etiological agent was confirmed as Acanthamoeba hatchetti by use of diversity profiling based on a next-generation sequencing approach.
Huang J, Zhao Y, Shiraigol W, Li B, Bai D, Ye W, Daidiikhuu D, Yang L, Jin B, Zhao Q, Gao Y, Wu J, Bao W, Li A, Zhang Y, Han H, Bai H, Bao Y, Zhao L....Karyotypic diversification is more prominent in Equus species than in other mammals. Here, using next generation sequencing technology, we generated and de novo assembled quality genomes sequences for a male wild horse (Przewalski's horse) and a male domestic horse (Mongolian horse), with about 93-fold and 91-fold coverage, respectively. Portion of Y chromosome from wild horse assemblies (3 M bp) and Mongolian horse (2 M bp) were also sequenced and de novo assembled. We confirmed a Robertsonian translocation event through the wild horse's chromosomes 23 and 24, which contained sequences th...
Moreton J, Malla S, Aboobaker AA, Tarlinton RE, Emes RD.The immune system of the horse has not been well studied, despite the fact that the horse displays several features such as sensitivity to bacterial lipopolysaccharide that make them in many ways a more suitable model of some human disorders than the current rodent models. The difficulty of working with large animal models has however limited characterisation of gene expression in the horse immune system with current annotations for the equine genome restricted to predictions from other mammals and the few described horse proteins. This paper outlines sequencing of 184 million transcriptome sh...
Bujacz A, Zielinski K, Sekula B.Serum albumin, a protein naturally abundant in blood plasma, shows remarkable ligand binding properties of numerous endogenous and exogenous compounds. Most of serum albumin binding sites are able to interact with more than one class of ligands. Determining the protein-ligand interactions among mammalian serum albumins is essential for understanding the complexity of this transporter. We present three crystal structures of serum albumins in complexes with naproxen (NPS): bovine (BSA-NPS), equine (ESA-NPS), and leporine (LSA-NPS) determined to 2.58 Å (C2), 2.42 Å (P61), and 2.73 Å (P2₁2₁...
Tallmadge RL, Tseng CT, Felippe MJ.To further studies of neonatal immune responses to pathogens and vaccination, we investigated the dynamics of B lymphocyte development and immunoglobulin (Ig) gene diversity. Previously we demonstrated that equine fetal Ig VDJ sequences exhibit combinatorial and junctional diversity levels comparable to those of adult Ig VDJ sequences. Herein, RACE clones from fetal, neonatal, foal, and adult lymphoid tissue were assessed for Ig lambda light chain combinatorial, junctional, and sequence diversity. Remarkably, more lambda variable genes (IGLV) were used during fetal life than later stages and I...
Bigi D, Perrotta G, Zambonelli P.To understand the origin and genetic diversity of Italian horses, mitochondrial DNA D-loop sequences were generated for 163 horses from seven breeds. Sequence analysis of a 480-bp segment revealed a total of 84 haplotypes with 57 polymorphic sites, indicating multiple maternal origins and high genetic diversity. Comparison of the haplotypes with the equine mtDNA haplotype/haplogroup nomenclature showed a haplogroup distribution in the Italian breeds more similar to that found in the Middle East breeds than in the European breeds, probably due to the economic and cultural relationship with the ...
Boyko AR, Brooks SA, Behan-Braman A, Castelhano M, Corey E, Oliveira KC, Swinburne JE, Todhunter RJ, Zhang Z, Ainsworth DM, Robinson NE.Equine recurrent laryngeal neuropathy (RLN) is a bilateral mononeuropathy with an unknown pathogenesis that significantly affects performance in Thoroughbreds. A genetic contribution to the pathogenesis of RLN is suggested by the higher prevalence of the condition in offspring of RLN-affected than unaffected stallions. To better understand RLN pathogenesis and its genetic basis, we performed a genome-wide association (GWAS) of 282 RLN-affected and 268 control Thoroughbreds. Results: We found a significant association of RLN with the LCORL/NCAPG locus on ECA3 previously shown to affect body siz...
Kim MC, Lee SW, Ryu DY, Cui FJ, Bhak J, Kim Y.The role of microRNAs (miRNAs) as a post-transcriptional gene regulator has been elucidated in a broad range of organisms including domestic animals. Characterization of miRNAs in normal tissues is an important step to investigate the functions of miRNAs in various physiological and pathological conditions. Using Illumina Next Generation Sequencing (NGS) technology, we identified a total of 292 known and 329 novel miRNAs in normal horse tissues including skeletal muscle, colon and liver. Distinct sets of miRNAs were differentially expressed in a tissue-specific manner. The miRNA genes were dis...
Song SD, Barker SC, Shao R.The genus Haematopinus contains 21 species of blood-sucking lice, parasitizing both even-toed ungulates (pigs, cattle, buffalo, antelopes, camels and deer) and odd-toed ungulates (horses, donkeys and zebras). The mitochondrial genomes of the domestic pig louse, Haematopinus suis, and the wild pig louse, Haematopinus apri, have been sequenced recently; both lice have fragmented mitochondrial genomes with 37 genes on nine minichromosomes. To understand whether the composition of mitochondrial minichromosomes and the gene content and gene arrangement of each minichromosome are stable within the g...
Sharma R, Livesey MR, Wyllie DJ, Proudfoot C, Whitelaw CB, Hay DC, Donadeu FX.Pluripotent stem cells (PSCs) offer unprecedented biomedical potential not only in relation to humans but also companion animals, particularly the horse. Despite this, attempts to generate bona fide equine embryonic stem cells have been unsuccessful. A very limited number of induced PSC lines have so far been generated from equine fibroblasts but their potential for directed differentiation into clinically relevant tissues has not been explored. In this study, we used retroviral vectors to generate induced pluripotent stem cells (iPSCs) with comparatively high efficiency from equine keratinocy...
Park W, Kim J, Kim HJ, Choi J, Park JW, Cho HW, Kim BW, Park MH, Shin TS, Cho SK, Park JK, Kim H, Hwang JY, Lee CK, Lee HK, Cho S, Cho BW.Previous studies of horse RNA-seq were performed by mapping sequence reads to the reference genome during transcriptome analysis. However in this study, we focused on two main ideas. First, differentially expressed genes (DEGs) were identified by de novo-based analysis (DBA) in RNA-seq data from six Thoroughbreds before and after exercise, here-after referred to as "de novo unique differentially expressed genes" (DUDEG). Second, by integrating both conventional DEGs and genes identified as being selected for during domestication of Thoroughbred and Jeju pony from whole genome re-sequencing (WG...
Iqbal K, Chitwood JL, Meyers-Brown GA, Roser JF, Ross PJ.Formation of the inner cell mass (ICM) and trophectoderm (TE) marks the first differentiation event in mammalian development. These two cell types have completely divergent fates for the remainder of the developmental process. The molecular mechanisms that regulate ICM and TE formation are poorly characterized in horses. The objective of this study was to establish the transcriptome profiles of ICM and TE cells from horse blastocysts using RNA sequencing (RNA-seq). A total of 12 270 genes were found to be expressed in either lineage. Global analysis of the transcriptome profiles by unsupervi...
Desjardin C, Chat S, Gilles M, Legendre R, Riviere J, Mata X, Balliau T, Esquerré D, Cribiu EP, Betch JM, Schibler L.Osteochondrosis (OC) is a developmental bone disorder affecting several mammalian species including the horse. Equine OC is described as a focal disruption of endochondral ossification, leading to osteochondral lesions (osteochondritis dissecans, OCD) that may release free bodies within the joint. OCD lesions trigger joint swelling, stiffness and lameness and affects about 30% of the equine population. OCD is considered as multifactorial but its physiopathology is still poorly understood and genes involved in genetic predisposition are still unknown. Our study compared two healthy and two OC-a...
Gabrielyan A, Knaak S, Gelinsky M, Arnhold S, Rösen-Wolff A.In vivo tissue regeneration depends on migration of stem cells into injured areas, their differentiation into specific cell types, and their interaction with other cells that are necessary to generate new tissue. Human mesenchymal stem cells, a subset of bone marrow stromal cells (BMSCs), can migrate and differentiate into osteoblasts in bone tissue. This can be facilitated by recombinant growth factors and cytokines. In many animal species, the availability of genomic sequences, recombinant proteins, and/or antibodies is limited so that new approaches are needed to generate resources that fac...
Blott SC, Swinburne JE, Sibbons C, Fox-Clipsham LY, Helwegen M, Hillyer L, Parkin TD, Newton JR, Vaudin M.Thoroughbred racehorses are subject to non-traumatic distal limb bone fractures that occur during racing and exercise. Susceptibility to fracture may be due to underlying disturbances in bone metabolism which have a genetic cause. Fracture risk has been shown to be heritable in several species but this study is the first genetic analysis of fracture risk in the horse. Results: Fracture cases (n = 269) were horses that sustained catastrophic distal limb fractures while racing on UK racecourses, necessitating euthanasia. Control horses (n = 253) were over 4 years of age, were racing during the s...
Lecis R, Tore G, Scagliarini A, Antuofermo E, Dedola C, Cacciotto C, Dore GM, Coradduzza E, Gallina L, Battilani M, Anfossi AG, Muzzeddu M, Chessa B....We detected a novel papillomavirus (EaPV1) from healthy skin and from sun associated cutaneous lesions of an Asinara (Sardinia, Italy) white donkey reared in captivity in a wildlife recovery centre. The entire genome of EaPV1 was cloned, sequenced, and characterised. Genome is 7467 bp long, and shows some characteristic elements of horse papillomaviruses, including a small untranslated region between the early and late regions and the lack of the retinoblastoma tumour suppressor binding domain LXCXE in E7. Additionally, a typical E6 ORF is missing. EaPV1 DNA was detected in low copies in norma...
Corbin LJ, Kranis A, Blott SC, Swinburne JE, Vaudin M, Bishop SC, Woolliams JA.Despite the dramatic reduction in the cost of high-density genotyping that has occurred over the last decade, it remains one of the limiting factors for obtaining the large datasets required for genomic studies of disease in the horse. In this study, we investigated the potential for low-density genotyping and subsequent imputation to address this problem. Results: Using the haplotype phasing and imputation program, BEAGLE, it is possible to impute genotypes from low- to high-density (50K) in the Thoroughbred horse with reasonable to high accuracy. Analysis of the sources of variation in imput...
Wang W, Wang S, Hou C, Xing Y, Cao J, Wu K, Liu C, Zhang D, Zhang L, Zhang Y, Zhou H.Recent studies have found that copy number variations (CNVs) are widespread in human and animal genomes. CNVs are a significant source of genetic variation, and have been shown to be associated with phenotypic diversity. However, the effect of CNVs on genetic variation in horses is not well understood. In the present study, CNVs in 6 different breeds of mare horses, Mongolia horse, Abaga horse, Hequ horse and Kazakh horse (all plateau breeds) and Debao pony and Thoroughbred, were determined using aCGH. In total, seven hundred CNVs were identified ranging in size from 6.1 Kb to 0.57 Mb across a...
Sangal V, Jones AL, Goodfellow M, Sutcliffe IC, Hoskisson PA.Rhodococcus equi ('Prescottella equi') is a pathogenic actinomycete primarily infecting horses but has emerged as an opportunistic human pathogen. We have sequenced the genome of the type strain of this species, R. equi strain C7(T) , and compared the genome with that of another foal isolate 103S and of a human isolate ATCC 33707. The R. equi strains are closely related to each other and yet distantly related to other rhodococci and Nocardia brasiliensis. The comparison of gene contents among R. equi strains revealed minor differences that could be associated with host adaptation from foals to...
Fornal A, Radko A, Piestrzyńska-Kajtoch A.Short tandem repeat (STR) loci, i.e. microsatellites are a class of genetic markers commonly used for population studies and parentage control. This study determined the usefulness of microsatellite markers recommended by International Society for Animal Genetics (ISAG) for identification and pedigree analysis in horses based on the example of Polish Hucul horse population (Equus caballus). The set of seventeen microsatellites loci was tested (AHT4, AHT5, ASB2, HMS2, HMS3, HMS6, HMS7, HTG10, HTG4, HTG6, HTG7, VHL20, ASB17, ASB23, CA425, HMS1, LEX3) for 216 individuals. All samples were genotyp...
O'Donnell MM, Harris HM, O'Toole PW, Ross RP.We report the draft genome sequence of Lactobacillus equi strain DPC6820, isolated from equine feces. L. equi is a predominant Lactobacillus species in the horse hindgut microbiota. An examination of the genome identified genes and enzymes highlighting L. equi adaptations to the herbivorous gastrointestinal tract of the horse, including fructan hydrolases. This genome sequence may help us further understand the microbial ecology of the equine hindgut and the influence lactobacilli have on it.
Thomas KC, Hamilton NA, North KN, Houweling PJ.The sarcomeric α-actinins, encoded by the genes ACTN2 and ACTN3, are major structural components of the Z-line and have high sequence similarity. α-Actinin-2 is present in all skeletal muscle fibres, while α-actinin-3 has developed specialized expression in only type 2 (fast, glycolytic) fibres. A common single nucleotide polymorphism (SNP) in the human ACTN3 gene (R577X) has been found to influence muscle performance in elite athletes and the normal population. For this reason, equine ACTN3 (eACTN3) is considered to be a possible candidate that may influence horse performance. In this stud...
Capomaccio S, Vitulo N, Verini-Supplizi A, Barcaccia G, Albiero A, D'Angelo M, Campagna D, Valle G, Felicetti M, Silvestrelli M, Cappelli K.The horse is an optimal model organism for studying the genomic response to exercise-induced stress, due to its natural aptitude for athletic performance and the relative homogeneity of its genetic and environmental backgrounds. Here, we applied RNA-sequencing analysis through the use of SOLiD technology in an experimental framework centered on exercise-induced stress during endurance races in equine athletes. We monitored the transcriptional landscape by comparing gene expression levels between animals at rest and after competition. Overall, we observed a shift from coding to non-coding regio...
Kinoshita Y, Niwa H, Katayama Y, Hariu K.Obligate anaerobes are important etiological agents in pneumonia or pleuropneumonia in horses, because they are isolated more commonly from ill horses that have died or been euthanized than from those that survive. We performed bacterial identification and antimicrobial susceptibility testing for obligate anaerobes to establish effective antimicrobial therapy. We used 16S rRNA gene sequencing to identify 58 obligate anaerobes and compared the results with those from a phenotypic identification kit. The identification results of 16S rRNA gene sequencing were more reliable than those of the comm...
Yin X, Lin Y, Cai W, Wei P, Wang X.Equine infectious anemia virus (EIAV) is an important animal model for understanding the relationship between viral persistence and the host immune response during lentiviral infections. Comparison and analysis of the codon usage model between EIAV and its hosts is important for the comprehension of viral evolution. In our study, the codon usage pattern of EIAV was analyzed from the available 29 full-length EIAV genomes through multivariate statistical methods. Results: Effective number of codons (ENC) suggests that the codon usage among EIAV strains is slightly biased. The ENC-plot analysis d...
Hendrickson SL.Life at high altitude results in physiological and metabolic challenges that put strong evolutionary pressure on performance due to oxidative stress, UV radiation and other factors dependent on the natural history of the species. To look for genes involved in altitude adaptation in a large herbivore, this study explored genome differentiation between a feral population of Andean horses introduced by the Spanish in the 1500s to the high Andes and their Iberian breed relatives. Results: Using allelic genetic models and Fst analyses of ~50 K single nucleotide polymorphisms (SNPs) across the horse...
Al-Jaru A, Goodwin W, Skidmore J, Khazanehdari K.Advances in molecular cytogenetics have provided the opportunity to study events during prophase I of meiosis. Immunofluorescent localization of different meiotic protein components were used to characterize the early stages of the first meiotic division in horse spermatocytes. The frequency and distribution of recombination events during prophase I were investigated using the mutL homolog 1 (MLH1) protein that is known to be associated with these events. The frequency and distribution of MLH1 foci were investigated in pachytene nuclei of 6 fertile stallions, and the average relative synaptone...
Towers RE, Murgiano L, Millar DS, Glen E, Topf A, Jagannathan V, Drögemüller C, Goodship JA, Clarke AJ, Leeb T.Ectodermal dysplasias (EDs) are a large and heterogeneous group of hereditary disorders characterized by abnormalities in structures of ectodermal origin. Incontinentia pigmenti (IP) is an ED characterized by skin lesions evolving over time, as well as dental, nail, and ocular abnormalities. Due to X-linked dominant inheritance IP symptoms can only be seen in female individuals while affected males die during development in utero. We observed a family of horses, in which several mares developed signs of a skin disorder reminiscent of human IP. Cutaneous manifestations in affected horses includ...
Puchalska M, Witkowska-Piłaszewicz O.Gene doping, the use of gene therapy or genetic manipulation to enhance athletic performance, has emerged as a potential threat to the integrity and welfare of equine sports, such as horse racing and equestrian sports. This review aims to provide an overview of gene doping in horses, including the underlying technologies, potential applications, detection methods, ethical concerns and future perspectives. By understanding the current landscape of gene doping in horses, stakeholders can work together to develop strategies to safeguard the integrity of equine sports.
Hurni JI, Kaiser-Thom S, Gerber V, Keller JE, Collaud A, Fernandez J, Schwendener S, Perreten V.A total of 100 nasal swabs were collected from healthy horses in Switzerland between January 2020 and August 2020. The samples were taken from horses at 40 different stables in 12 different cantons and screened for both methicillin-resistant (MRSA) and methicillin-susceptible S. aureus (MSSA) using selective agar plates. S. aureus were tested for antibiotic susceptibility by measurement of the minimal inhibitory concentration (MIC) and for virulence factors, antibiotic resistance genes and phylogenetic characteristics using whole genome sequence analysis. Ten horses were found to be positiv...
Lee J, Kang YJ, Kim YK, Choi JY, Shin SM, Shin MC.The influences of diet and environmental factors on gut microbial profiles have been widely acknowledged; however, the specific roles of host genetics remain uncertain. To unravel host genetic effects, we raised 47 Jeju crossbred (Jeju × Thoroughbred) foals that exhibited higher genetic diversity. Foals were raised under identical environmental conditions and diets. Microbial composition revealed that Firmicutes, Bacteroidetes, and Spirochaetes were the predominant phyla. We identified 31 host-microbiome associations by utilizing 47,668 single nucleotide polymorphisms (SNPs) and 734 taxa with...
Manzoori S, Farahani AHK, Moradi MH, Kazemi-Bonchenari M.The assignment of an individual to the true population of origin using a low-panel of discriminant SNP markers is one of the most important applications of genomic data for practical use. The aim of this study was to evaluate the potential of different Artificial Neural Networks (ANNs) approaches consisting Deep Neural Networks (DNN), Garson and Olden methods for feature selection of informative SNP markers from high-throughput genotyping data, that would be able to trace the true breed of unknown samples. The total of 795 animals from 37 breeds, genotyped by using the Illumina SNP 50k Bead ch...
MacFadyen AC, Waller AS, Paterson GK.Strain 28462T, which had Gram-stain-positive, catalase-negative coccus-shaped cells, was isolated from a routine tracheal sample from a 3 year old thoroughbred horse. 16S rRNA gene sequence analysis revealed it to be most closely related to, but distinct from, Streptococcus henryi (95.7 % identity), Streptococcusplurextorum (95.8 %), Streptococcusporci (96.4 %) and Streptococcus caprae (95.1 %). Similarity values derived from sequences from sodA and rpoB genes were consistent with strain 28462T belonging to a species distinct from these four streptococci. At the whole genome level, str...
Vdovina NV, Yuryeva IB.Mezenskaya horse (Mezenka) is Russia's aboriginal breed. It is a domestic selection in the northern territories of Arkhangelsk region. The breed is perfectly adapted to the conditions of the Far North, and has a number of valuable economic and biological qualities. At present, it has a limited gene pool and is bred only in the Mezensky district, where one gene pool-breeding farm is operating and so is a number of basic farms, where selection and breeding activities take place with the breed. Due to a small population of Mezen horses, the challenge of preserving its intra-breed diversity is ver...
Kinoshita Y, Niwa H, Uchida-Fujii E, Nukada T.Mycoplasma felis causes conjunctivitis in cats and respiratory diseases in horses. We report here the complete genome assembly of equine Mycoplasma felis strain Myco-2, which was isolated from an ill horse in Japan.
Nemoto M, Nagai M, Tsunemitsu H, Omatsu T, Furuya T, Shirai J, Kondo T, Fujii Y, Todaka R, Katayama K, Mizutani T.Equine group A rotavirus (RVA) G3P[12] and G14P[12] strains cause gastroenteritis in foals worldwide. Both of these strains have been co-circulating in Japan since G14P[12] strains emerged in the late 1990s. Although it is important to comprehensively understand the evolution of RVA strains, whole-genome sequence data on recent equine RVA strains in Japan are lacking. Therefore, in this study, whole-genome analysis of 23 equine RVA isolates from the late 1990s and 2009-2010 and the vaccine strain RVA/Horse-tc/JPN/HO-5/1982/G3P[12] (HO-5) was performed. The G3 strains, including strain HO-5, sh...
Lee JH, Song KD, Kim JM, Leem HK, Park KD.Jeju horse (Natural Monument number 347) is a breed of horse that has experienced long-term isolation and domestication in Jeju Island, South Korea. We evaluated genetic features of this breed, including SNP, by whole-genome resequencing using an Illumina HiSeq 2000. A total of 5,986,852 SNP were identified in 4 Jeju horses and were divided into homozygous and heterozygous SNP (2,357,099 and 3,629,753 SNP, respectively). It revealed that 63.8% of these SNP resided in intergenic regions. Immune response genes with nonsynonymous SNP were overrepresented in Jeju horses as evidenced by Gene Ontolo...
Williams H, Richards CM, Konfortov BA, Miller JR, Tucker EM.In a study of 35 horse-mouse heterohybridoma cell lines, synteny in the horse was found between LDHB, PEPB and IGF1 and between NP, MPI and IDH2. A synteny between ADA and PEPC was also indicated. The loci for horse immunoglobulin light chain (IgL) genes and for LDHA were independent.
Denham J.Telomeres are genetically conserved nucleoprotein complexes located at the ends of chromosomes that preserve genomic stability. In large mammals, somatic cell telomeres shorten with age, owing to the end replication problem and lack of telomere-lengthening events (e.g. telomerase and ALT activity). Therefore, telomere length reflects cellular replicative reserve and mitotic potential. Environmental insults can accelerate telomere attrition in response to cell division and DNA damage. As such, telomere shortening is considered one of the major hallmarks of ageing. Much effort has been dedicate...
Denham J, Stevenson K, Denham MM.Telomeres are genetically conserved repetitive terminal DNA that protect against genomic instability and shorten with ageing. Here, we reveal the leukocyte telomere length of Equus caballus by measuring terminal restriction fragments (TRFs) using Southern Blot analysis in a cohort of 43 Thoroughbred horses (age: 24 h-25 years). Heterogeneous TRFs were observed in each animal and large inter-animal variation in mean TRF was observed (range: 10.5-18.7 kbp). Mean TRFs were inversely correlated with age (r = -0.47). The estimated yearly rate of telomere attrition was 134 bp. Horses shoul...
Cothran EG, van Dyk E, van der Merwe FJ.Genetic variation at 7 blood-group and 10 biochemical genetic loci was examined in 30 horses from a feral herd from the Namib Desert of Namibia, Africa. The observed genetic variability was extremely low compared with that found in domestic horse breeds. The low variation was most probably a result of recent small population size and a small founding population size. Genetic comparison of the Namib horses, which were of unknown origins, to domestic horse breeds, showed that the Namib horses had the highest genetic similarity to Arabian type horses, although they did not closely resemble this t...
Baena MM, Diaz S, Moura RS, Meirelles SLC.The Mangalarga Marchador (MM) horse breed has expressive importance in the Brazilian economy. Thus, the aim of this study was to investigate diversity in the MM breed. A database with a total of 3,193 genotyped horses was used (MM, n = 2,829; Andalusian - AND, n = 67; Pure Blood Lusitano - LUS, n = 43; English Thoroughbred - THO, n = 54; Arabian - ARA, n = 99; Campolina - CAM, n = 61; and Mangalarga - MAN, n = 40) for 13 microsatellite. Diversity parameters were estimates, such as mean number of alleles (Nm) and the number of rare alleles (AR), expected heterozygosity (He), F statistics...