Horse breeds represent the diverse genetic and phenotypic variations found within the species Equus ferus caballus. These breeds are categorized based on characteristics such as size, conformation, coat color, and temperament, which have been selectively bred over centuries to fulfill specific roles and functions. Common classifications of horse breeds include light horses, draft horses, and ponies, each serving different purposes ranging from riding and racing to work and companionship. This page aggregates peer-reviewed research studies and scholarly articles that explore the genetics, history, and functional attributes of various horse breeds, as well as their impact on equine management and breeding practices.
Valera M, Encina A, Sánchez-Guerrero MJ, Rodríguez-Sainz de Los Terreros A, Bartolomé E.Behavioral and emotional reactivity assessment in sport horses is essential for optimizing their management and sports performance, particularly in equestrian disciplines such as Dressage. This study investigates, in Pura Raza Española (PRE) horses, the association between facial hair whorl (FHW) patterns, behavioral traits, and physiological stress responses using ocular temperature (OT) assessed with infrared thermography as, an objective, non-invasive physiological stress indicator. Unassigned: A total of 98 male PRE horses, aged 4-6 years old and all gray coated, were evaluated during the...
Naito M, Nishihata S, Amano T.To investigate the factors affecting the utilization of retired Thoroughbred racehorses in equestrian disciplines, Bayesian linear mixed models were separately fitted using rank, round time, and obstacle faults from show-jumping competitions restricted to retired Thoroughbred racehorses as dependent variables, with the interaction between horse sex and the interval from race retirement to competition (as a proxy for transition training to show-jumping) as a fixed effect. When the interval was short (≤1 year), the estimated marginal mean of rank was statistically significantly lower in stalli...
Kim T, Lee S, Seo JP.Foot diseases are common causes of lameness in horses. Computed tomography (CT) is a valuable tool for diagnosing musculoskeletal lesions in horses and providing a detailed evaluation of foot diseases. Objective: The objective of this study was to establish reference ranges related to the feet of normal Jeju horses by measuring the angles and length of the hoof, and the Hounsfield Unit (HU) value of soft tissues in the foot. Methods: Sixteen normal Jeju horses (mean age: 4.25 years; mean body weight: 282.06 kg) without lameness were examined using CT. After CT scanning, the angles and lengths ...
Calle-González N, Rivero JL, Argüelles D, Requena F, Muñoz A.Capacitive resistive electrical transfer (CRET) is a non-invasive electromagnetic diathermic technique. The effect of its application 24 h prior to exercise, compared to a sham application performed with the device off, was evaluated in 8 Spanish Purebred dressage stallions. CRET was applied bilaterally on the neck, back, and croup. The horses wore an accelerometer fixed on the sternal area during a dressage test, and spatiotemporal stride parameters, total and dorsoventral (DVAA), longitudinal (LAA), and mediolateral accelerometric activities, as well as dorsoventral displacement, were recor...
The research aims to study the dynamics of reproductive system pathologies in mares of Kazakh and Mugalzhar horse breeds and their impact on the reproductive traits of the breeding stock. The object of the research was horses of the Kazakh and Mugalzhar breeds. The formation of experimental groups was carried out using the pair-analog method. It was found that the frequency of detection of infertile mares is 13.8-25.0%. Subinvolution of the uterus from the total number of infertile mares is 8.3-10.7%, endometritis - 16.6-23.3%, atony and hypotonia of the uterus - 8.3-13.3%, ovarian diseases - ...
Choi Y, Jung Y, Wickens CL, Yoon M.Horses are social animals, with early life experiences playing a crucial role in their physiological and behavioral development. This study explored the influence of herd dynamics and foundational training on behavioral and hormonal changes in weaned foals. We examined 13 six-month-old Quarter Horse foals over a three-month training period, performing behavioral observations, temperament assessments, and hormone analyses at the start, midpoint, and end of the training. The results indicated that affiliative behaviors decreased significantly, while agonistic behaviors first increased and then d...
Gmel AI, Haraldsdóttir EH, Rosa TV, Lamas LP, Neuditschko M, Weishaupt MA.Europe has many horse breeds differing in conformation, gaits and genetics due to diverging breeding goals. Research studies comparing objective gait parameters between different horse breeds are limited and date back a decade. Objective: In this study, objective gait parameters were measured in three European breeds, namely Lusitanos (LUS; n = 52), Franches-Montagnes (FM; n = 311) and Swiss Warmblood (WB; n = 40) using an inertial measurement system (sensors at poll, withers, pelvis and all four canon bones) at walk and trot. Results: At walk and trot, LUS moved significantly slower than WB a...
Saldaña CL, Justo S, Murga L, Vásquez HV, Maicelo JL, Arbizu CI, Bardales W.The complete mitochondrial genome of the Peruvian Paso Horse was assembled using PacBio HiFi long reads, resulting in a high-quality circular genome of 16,617 bp comprising 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and a control region. Nucleotide composition and gene structure were consistent with other equine mitogenomes. Codon usage analysis revealed a bias toward CUA (Leu), AUA and AUC (Ile), suggesting translational optimization. Thirty-five heteroplasmic variants were identified, predominantly located in RNA genes (12 S rRNA and tRNA-Phe), with allele frequencies between 0.10 and 0.6...
Rönnow E, Roth LSV.Compared to other companion animals, our understanding of the human-horse relationship is limited, particularly from the horse's perspective. This pilot study examined whether horses (N = 30) show a bias towards their owner in a reunion in the presence of both the owner and a stranger. Afterwards, the horses were also presented with the odor of the owner and a stranger. Both tests were video recorded for behavioral analyzation. No significant owner-directed bias was observed at the group level in either the reunion test or the odor test. Nonetheless, in the reunion test, owner bias in physical...
Pepper B, North E, Culwell J, Nicodemus MC, Cavinder C, Harvey K, Williams T.Due to the incorporation of the Golden American Saddlebred Horse Association (GASHA) into the American Saddlebred Horse and Breeders Association (ASHBA), breeding for coat color has become more challenging for horse breeders. However, with this merger, pedigree tracing can be of value in pinpointing foundation bloodlines within the GASHA that influence production of the golden coat phenotype. Objective: The study objective was to document the historical origins of the GASHA through pedigree tracing to determine the influence of dilution alleles that produce the golden coat phenotype. Methods: ...
Chessari G, Reich P, Criscione A, Falker-Gieske C, Mastrangelo S, Tumino S, Bordonaro S, Marletta D, Tetens J.Single nucleotide polymorphism (SNP) arrays are commonly used for studying the genomic structure and diversity of livestock breeds, but whole-genome sequencing (WGS) provides higher-resolution genomic data. Genotype imputation has become a standard practice for increasing the genomic resolution of association studies. This work aimed to extend imputation to biodiversity analyses, comparing SNP array data before and after imputation. A 40 k SNP dataset of 281 horses from 12 breeds (DS) was imputed to sequence-level using a reference panel of 327 sequenced individuals, generating approximately 9...
Moghbeli Damane M, Ayatollahi Mehrgardi A, Esmailizadeh A, Momen M.Inbreeding is caused by mating between related individuals and is associated with reduced fitness and performance. Generally, in the horse population, inbreeding is caused by geographically restricted areas and intensive natural or artificial selection. For this reason, assessing accurate inbreeding is essential for developing and implementing effective breeding strategies aimed at preserving genetic diversity and reducing the harmful consequences of inbreeding. One of the most accurate approaches for assessing genomic inbreeding and autozygosity is through the analysis of runs of homozygosity...
Stachurska A, Wnuk E, Łuszczyński J, Donderowicz W.Correct conformation and symmetry of bilateral hooves are associated with a properly balanced hoof, which has a significant impact on the biomechanics of movement and reduces the risk of injury. The aim of the study was to compare solear aspect dimensions of bilateral hooves in forelimbs (hoof width, length, frog width, length, medial and lateral diagonals) with regard to sex, breed and age of horses. The dimensions were measured with a calliper in 100 horses of four breeds. The results showed that the breed factor significantly affected all dimensions. Age was significant for some variables, ...
Pennington MV, Zoller JL, White-Springer SH, Harlin JF, Huseman CJ, Leatherwood JL, O'Reilly CL.Competition stress is a common factor influencing the success of performing athletes. However, few studies have quantified the physiological stress responses in horses and riders surrounding an equestrian event. Objective: The objectives of the current study were to determine salivary cortisol concentrations (SCC) as an indicator of stress in fifteen horse and rider pairs competing in western stock horse events and to investigate the relationship between SCC and performance. Methods: Subjects included male and female Quarter horses aged 3-15 years and equestrians aged 18-22 years. Salivary sam...
Zuluaga-Cabrera AM, Barbosa da Costa G, Martinez ID, Arias MP.Colombian Paso horses (CPs) excel in gait competitions due to their endurance, speed, and precision, which demand a high level of cardiorespiratory fitness. However, their training regimes often lack scientific support, and few studies have linked physiological parameters to optimal training zones. This study aimed to estimate the aerobic lactate threshold (LTaer) using mathematical methods and to correlate it with heart rate (HR) zones and blood lactate. Eighteen CPs were evaluated and classified into trained (GT) and untrained (GD) groups. All animals underwent a field-based incremental exer...
Taned M, Zandi MB, Salek Ardestani S, Abdoli M, Spangler ML.Race performance in Thoroughbred horses is influenced by both genetic and environmental factors. Understanding their genetic architecture is essential for designing effective breeding programs. Objective: This study aimed to estimate genetic parameters and trends for key performance traits in Iranian Thoroughbred racehorses. Methods: Performance data, including race completion time (RCT), rank at the end of the competition (REC), and average speed (AS), were obtained from the Iranian Equestrian Federation (2002-2021). Pedigree data from 14,391 individuals were analyzed using CFC software. Gene...
Lewczuk D, Borowska A, Andruszkiewicz J, Bagnicka E.Breeding value estimations of Warmblood horses in Poland are based on field performance, but the amount of stallions' data is still insufficient (334 horses). The first study's aim is to compare stallions' results in different stages and evaluate the overall ability using both stages. The effects on preselection (first stage free movement) and performance tests (second stage under rider) were analyzed separately and together as the overall ability. Spearman correlations were evaluated. The second aim was to evaluate the training period on the results. Due to the pandemic and lack of tests, hor...
Frontiers in geneticsNovember 12, 2025
Volume 16 1439312 doi: 10.3389/fgene.2025.1439312
Tang C, Yang B, Dawulietihan G, Xue L, Liu S, Yalimaimaiti Y, Wang Q, Yang N, Sun X, Wang Y, Wumaier A, Khizat S, Assanbayev T, Kozhanov Z....Xinjiang is a region renowned for its rich diversity of native horse breeds, making it one of the most affluent equine genetic resource areas in China. While prized for their high adaptability and tolerance to roughage, the conservation of these native breeds faces challenges from the introduction of external breeds and industrial changes. Furthermore, the unknown population structure of Xinjiang horse breeds has hindered effective conservation efforts. Unassigned: This study presents the first comprehensive Single Nucleotide Polymorphism (SNP) analysis of seven Xinjiang native horse breeds. W...
Taylor DEF, Lancaster BE, Ellis AD.There are few 24 h time budgets for horses, especially for domesticated horses kept at pasture. Most time budgets utilise short-term scan sampling, which can miss behaviours. This study aimed to assess the seasonal variation in continuous behaviour of domesticated Icelandic horses at pasture during winter and spring in fair weather. Eight Icelandic horses (11.25 ± 9.19 years; 7 geldings, 1 stallion) were observed in a 26 acre field. Herd location and individual behaviour were continuously observed during 3 h periods amounting to 3 × 24 h in winter and late spring, compiled over 43 days (~21 ...
Schumacher A, Merle R, Stöckle S, Gehlen H.Polo is an equestrian sport with a long tradition, but to date there is little scientific data on health risks, particularly lameness. In an international online survey, 145 polo players (47.6% female, 52.4% male) with an average of 13.4 years of playing experience were questioned about lameness risks and influencing factors. The respondents reported a median of six horses, most frequently mares as their best-performing and healthiest animals. Horse age was significantly associated with the risk of lameness, increasing by approximately 19.5% per year (OR = 1.195; = 0.030) and differed dependi...
Stefaniuk-Szmukier M, Błaszczak A, Długosz B, Musiał A, Ropka-Molik K.The Silesian horse is a heavy warmblood breed developed in Polish Silesia through the covering of local mares by East Frisian and Oldenburg stallions. Because of its historical significance and genetic heritage, the breed is part of a conservation programme in Poland. One of the genetic disorders of concern in warmblood horses is fragile foal syndrome (FFS), an autosomal recessive disease caused by a mutation in the gene (c.2032G>A). Affected foals either perish in late pregnancy or are born with severe connective tissue abnormalities, leading to early death. As carriers do not exhibit sympto...
Sande A, Santosuosso E, Scharf JE, Shoemaker SJ, Temple S, Hemmerling K, Kell T, Leguillette R, Bayly WM.To compare maximal lactate steady-state (MLSS) speeds determined using a treadmill-dependent invasive reference method (RM) with 2 noninvasive methods based on heart rate variability-focused analysis of exercise ECGs. Unassigned: This was a randomized, blinded study using 7 fit Thoroughbreds. A standardized incremental exercise treadmill test (SET) where blood lactate concentration ([La]) was measured after every step facilitated calculation of speeds at which [La] was 1.5, 2.0, and 2.5 mmol/L. The RM required steady-state exercise (SS) at each of these speeds for 25 minutes or until [La] incr...
Ripollés-Lobo M, Perdomo-González DI, Azor P, Valera M.Investigate the genetic inbreeding depression load (IDL) on two dressage traits and two conformational defects in horses. Unassigned: The dataset included performance records for Walk and Points per Reprise (PPR) (N:43,838) and conformation data for Closed and Convergent hocks (N:57,949). Pedigree information spanned over 400,000 individuals. Inbreeding coefficients (F, F6, Fk) and partial inbreeding coefficient (Fij) were computed to quantify the IDL using Bayesian approach. Linear and ordinal logistic regressions were used to assess the relationship between inbreeding and phenotypic values. ...
Steensma MJ, Doekes HP, Derks MFL, Ducro BJ.In Friesian horses, withers height is an important trait as a minimum has been set to be eligible to the studbook. Several loci for withers height have been identified in horses. However, withers height has not been studied in the Friesian horse. Therefore, our aim was to identify loci associated with withers height in the Friesian horse population. We performed a genome-wide association study using 70 K SNP data of 2192 Friesian horses. We found ECA1 and ECA9 to be significantly associated with withers height, explaining 19.6% and 3.5% of the phenotypic variance, respectively. In other hors...
Wnuk E, Janicka W, Stachurska A, Owerczuk R, Łuszczyński J.Differences in the ranges and capacities of sensory modalities cause horses to perceive their surroundings differently than humans. To date, the horses' sense of smell has been studied mainly regarding social and reproductive behaviour. The role of olfaction in horse management and use also seems to be of utmost importance. The aim of this study was to determine the response to a scent of different intensities by horses of different sexes and types (warmblood horses vs ponies). The study involved 21 adult mares and geldings, of which 15 subjects learned how to complete the required task and we...
Gillen A, Hassel D, Gonzalez S, Savage V, Bauck A, Freeman D, Archer DC.Obstruction by strangulating lipoma (SLO) is one of the most common causes of small intestinal strangulation in horses and is fatal without surgery. Current knowledge of risk factors for SLO is limited to horse signalment features. To date, other risk factors have not been investigated. Objective: To investigate horse- and management-level risk factors for SLO using a population of healthy horses as controls. Methods: Matched, case-control study. Methods: A prospective, international multicentre study was conducted in the UK and USA between January 2022 and May 2024. Cases were horses with SLO...
Lewczuk D, Wypchło M, Hecold M, Buczkowska R, Korwin-Kossakowska A.Finding the causative mutations for musculoskeletal system development and health status is of a higher priority for all sport horse breeders' associations. Of the regulating proteins involved in animal ossification, 15 gene polymorphisms were chosen to be identified as connected with the nine fetlock and 14 hock bone structures measurements of 198 horses. All measurements were taken using X-rays of the limbs, which were available at the beginning and end of the horse training. The analysis of variance (GLM, SAS program) was performed taking into account identified training and horse-connected...
Mouncey R, de Mestre AM, Verheyen KL.Analyses of industry-level data suggest that around one-third of the UK and Ireland Thoroughbred foal crop fail to enter training. Prospective follow-up of individual horses could provide additional insight, particularly around individuals not attaining specific career milestones. Methods: A Thoroughbred birth cohort was established on stud farms across the UK and Ireland. Training, race performance, sales, export data, destinations and reasons for individuals failing to meet career milestones were collected from stud records, follow-up with owners, stud book and racing authorities' databases,...
Luštrek B, Šimon M, Turk K, Bogičević S, Potočnik K.In small, closed populations such as the Lipizzan horse, maintaining genetic diversity while limiting inbreeding is a key challenge in conservation breeding. The Lipizzan is an indigenous Slovenian breed with a small population and restricted gene flow from other subpopulations. Inbreeding is traditionally monitored with pedigree-based coefficients, but these often underestimate realised autozygosity, particularly when pedigree depth is limited. This study compared pedigree-based inbreeding (F_PED) with four genomic estimators (F_HOM, F_ROH, F_HBD, F_GRM) in 329 Slovenian Lipizzan horses genot...
Gu J, Orr N, Park SD, Katz LM, Sulimova G, MacHugh DE, Hill EW.Thoroughbred horses have been selected for exceptional racing performance resulting in system-wide structural and functional adaptations contributing to elite athletic phenotypes. Because selection has been recent and intense in a closed population that stems from a small number of founder animals Thoroughbreds represent a unique population within which to identify genomic contributions to exercise-related traits. Employing a population genetics-based hitchhiking mapping approach we performed a genome scan using 394 autosomal and X chromosome microsatellite loci and identified positively selec...
Brunberg E, Andersson L, Cothran G, Sandberg K, Mikko S, Lindgren G.The Silver coat color, also called Silver dapple, in the horse is characterized by dilution of the black pigment in the hair. This phenotype shows an autosomal dominant inheritance. The effect of the mutation is most visible in the long hairs of the mane and tail, which are diluted to a mixture of white and gray hairs. Herein we describe the identification of the responsible gene and a missense mutation associated with the Silver phenotype. Results: Segregation data on the Silver locus (Z) were obtained within one half-sib family that consisted of a heterozygous Silver colored stallion with 34...
Vidal MA, Kilroy GE, Johnson JR, Lopez MJ, Moore RM, Gimble JM.To characterize equine bone marrow (BM)-derived mesenchymal stem cell (MSC) growth characteristics and frequency as well as their adipogenic and osteogenic differentiation potential. Methods: In vitro experimental study. Methods: Foals (n=3, age range, 17-51 days) and young horses (n=5, age range, 9 months to 5 years). Methods: Equine MSCs were harvested and isolated from sternal BM aspirates and grown up to passage 10 to determine cell-doubling (CD) characteristics. Limit dilution assays were performed on primary and passaged MSCs to determine the frequency of colony-forming units with a fibr...
Schaefer RJ, Schubert M, Bailey E, Bannasch DL, Barrey E, Bar-Gal GK, Brem G, Brooks SA, Distl O, Fries R, Finno CJ, Gerber V, Haase B, Jagannathan V....To date, genome-scale analyses in the domestic horse have been limited by suboptimal single nucleotide polymorphism (SNP) density and uneven genomic coverage of the current SNP genotyping arrays. The recent availability of whole genome sequences has created the opportunity to develop a next generation, high-density equine SNP array. Using whole genome sequence from 153 individuals representing 24 distinct breeds collated by the equine genomics community, we cataloged over 23 million de novo discovered genetic variants. Leveraging genotype data from individuals with both whole genome sequence, ...
Cunningham EP, Dooley JJ, Splan RK, Bradley DG.The thoroughbred (TB) horse is one of the oldest breeds of domestic animals, with pedigree records spanning three centuries. Because the population is essentially closed, there is concern about loss of genetic variation. Here we report two parallel analyses. In the first, genetic variation in the current population is measured using data from 13 microsatellite loci in 211 horses with relationships calculated based on allele sharing. In the second analysis, pedigree information is used to calculate genetic relationships between animals based on shared ancestry. These two measures of relationshi...
Jamieson A, Taylor SC.Three general formulae calibrate the average capability of marker systems to dispute falsely reported pedigree records in uniparous species. The most familiar exclusion formula applies to paternity, although the same formula applies equally to maternity. Another formula faults the relationship of a single offspring with its putative parent; for example, where the genotype of the other parent is not available. The remaining formulae excludes both of the falsely recorded parents of a substituted offspring. Simplified forms of the three general formulae facilitate the calculation of maximal avera...
Lippold S, Matzke NJ, Reissmann M, Hofreiter M.DNA target enrichment by micro-array capture combined with high throughput sequencing technologies provides the possibility to obtain large amounts of sequence data (e.g. whole mitochondrial DNA genomes) from multiple individuals at relatively low costs. Previously, whole mitochondrial genome data for domestic horses (Equus caballus) were limited to only a few specimens and only short parts of the mtDNA genome (especially the hypervariable region) were investigated for larger sample sets. Results: In this study we investigated whole mitochondrial genomes of 59 domestic horses from 44 breeds an...
Johnson L, Thompson DL, Varner DD.Testicular function is under the control of expression and repression of several genes and gene products, and many of these works through Sertoli cells. The capability of Sertoli cells to regulate spermatogenesis is dependent on Sertoli cell functions and Sertoli cell number. Sertoli cell number has long been thought to be stable in adults with no proliferation of Sertoli cells once adult numbers have been reached. However, adult horses do not have stable Sertoli cell numbers, and new studies indicate that adult Sertoli cells can be made to re-enter mitotic phase under certain experimental con...
Aitken RJ, Gibb Z, Mitchell LA, Lambourne SR, Connaughton HS, De Iuliis GN.The prolonged incubation of human spermatozoa in vitro was found to induce a loss of motility associated with the activation of mitochondrial reactive oxygen species generation in the absence of any change in mitochondrial membrane potential. The increase in mitochondrial free radical production was paralleled by a loss of protein thiols and a concomitant rise in the formation of 4-hydroxynonenal, an electrophilic product of lipid peroxidation that was found to directly suppress sperm movement. These results prompted a search for nucleophiles that could counteract the action of such cytotoxic ...
Xu S, Luosang J, Hua S, He J, Ciren A, Wang W, Tong X, Liang Y, Wang J, Zheng X.To investigate genetic mechanisms of high altitude adaptations of animals living in the Tibetan Plateau, three mitochondrial genomes (mt-genome) of Tibetan horses living in Naqu (4,500 m) of Tibetan, Zhongdian (3,300 m) and Deqin (3,100 m) of Yunnan province were sequenced. The structures and lengths of these three mt-genomes are similar to the Cheju horse, which is related to Tibetan horses, but little shorter than the Swedish horse. The pair-wise identity of these three horses on nucleotide level is more than 99.3%. When the gene encoding the mitochondrial protein of Tibetan horses was analy...
Ivester KM, Couëtil LL, Moore GE.Mild equine asthma is presumed to arise in response to environmental exposures but the relative impact of differing inflammatory phenotypes upon performance are largely unexplored. Objective: Airway inflammation negatively affects performance and cytological phenotype varies with environmental exposure. Methods: Thoroughbred racehorses in active training and racing. Methods: Thoroughbreds were recruited 24-48 hours before racing. Each horse was eligible for re-enrollment with each race entry. Within one hour of race completion, physical examination, respiratory endoscopy, and BAL were performe...
Ball BA.Oxidative stress is an important component of the cytopathology of equine spermatozoa undergoing storage as liquid or frozen semen. Damage to chromatin, membranes and proteins of sperm are important components of oxidative damage to sperm. Similarly, sperm are exposed to a variety of osmotic stresses during storage that result from exposure to hypertonic media or result as a consequence of osmotic changes induced during freezing. A number of changes induced during processing and storage of equine sperm also appear to induce apoptotic-like changes which may adversely affect sperm survival and f...
Bellone RR, Holl H, Setaluri V, Devi S, Maddodi N, Archer S, Sandmeyer L, Ludwig A, Foerster D, Pruvost M, Reissmann M, Bortfeldt R, Adelson DL....Leopard complex spotting is a group of white spotting patterns in horses caused by an incompletely dominant gene (LP) where homozygotes (LP/LP) are also affected with congenital stationary night blindness. Previous studies implicated Transient Receptor Potential Cation Channel, Subfamily M, Member 1 (TRPM1) as the best candidate gene for both CSNB and LP. RNA-Seq data pinpointed a 1378 bp insertion in intron 1 of TRPM1 as the potential cause. This insertion, a long terminal repeat (LTR) of an endogenous retrovirus, was completely associated with LP, testing 511 horses (χ(2)=1022.00, p<<...
Plaza Davila M, Martin Muñoz P, Tapia JA, Ortega Ferrusola C, Balao da Silva C C, Peña FJ.Mitochondria have been proposed as the major source of reactive oxygen species in somatic cells and human spermatozoa. However, no data regarding the role of mitochondrial ROS production in stallion spermatozoa are available. To shed light on the role of the mitochondrial electron transport chain in the origin of oxidative stress in stallion spermatozoa, specific inhibitors of complex I (rotenone) and III (antimycin-A) were used. Ejaculates from seven Andalusian stallions were collected and incubated in BWW media at 37 °C in the presence of rotenone, antimycin-A or control vehicle. Incubation...
Evans SV, Brayer GD.The three-dimensional structure of horse heart metmyoglobin has been refined to a final R-factor of 15.5% for all observed data in the 6.0 to 1.9 A resolution range. The final model consists of 1242 non-hydrogen protein atoms, 154 water molecules and one sulfate ion. This structure has nearly ideal bonding and bond angle geometry. A Luzzati plot of the variation in R-factor with resolution yields an estimated mean co-ordinate error of 0.18 A. An extensive analysis of the pattern of hydrogen bonds formed in horse heart metmyoglobin has been completed. Over 80% of the polypeptide chain is involv...
Tinker MK, White NA, Lessard P, Thatcher CD, Pelzer KD, Davis B, Carmel DK.A prospective study of one year was conducted on 31 horse farms to obtain population based estimates of incidence, morbidity and mortality rates of equine colic. Farms with greater than 20 horses were enrolled by randomly selecting horse owners from 2 adjacent counties of Virginia and Maryland. Descriptive information for 1427 horses was collected at the initiation of the study and updated at 3 month intervals. Time on the farm during the study was tabulated for each horse. When colic was reported by the owner, investigators visited the farm to obtain information about the colic. The crude inc...
Ghosh S, Qu Z, Das PJ, Fang E, Juras R, Cothran EG, McDonell S, Kenney DG, Lear TL, Adelson DL, Chowdhary BP, Raudsepp T.We constructed a 400K WG tiling oligoarray for the horse and applied it for the discovery of copy number variations (CNVs) in 38 normal horses of 16 diverse breeds, and the Przewalski horse. Probes on the array represented 18,763 autosomal and X-linked genes, and intergenic, sub-telomeric and chrY sequences. We identified 258 CNV regions (CNVRs) across all autosomes, chrX and chrUn, but not in chrY. CNVs comprised 1.3% of the horse genome with chr12 being most enriched. American Miniature horses had the highest and American Quarter Horses the lowest number of CNVs in relation to Thoroughbred r...
Wallner B, Vogl C, Shukla P, Burgstaller JP, Druml T, Brem G.The paternally inherited Y chromosome displays the population genetic history of males. While modern domestic horses (Equus caballus) exhibit abundant diversity within maternally inherited mitochondrial DNA, no significant Y-chromosomal sequence diversity has been detected. We used high throughput sequencing technology to identify the first polymorphic Y-chromosomal markers useful for tracing paternal lines. The nucleotide variability of the modern horse Y chromosome is extremely low, resulting in six haplotypes (HT), all clearly distinct from the Przewalski horse (E. przewalskii). The most wi...
Janečka JE, Davis BW, Ghosh S, Paria N, Das PJ, Orlando L, Schubert M, Nielsen MK, Stout TAE, Brashear W, Li G, Johnson CD, Metz RP, Zadjali AMA....Dynamic evolutionary processes and complex structure make the Y chromosome among the most diverse and least understood regions in mammalian genomes. Here, we present an annotated assembly of the male specific region of the horse Y chromosome (eMSY), representing the first comprehensive Y assembly in odd-toed ungulates. The eMSY comprises single-copy, equine specific multi-copy, PAR transposed, and novel ampliconic sequence classes. The eMSY gene density approaches that of autosomes with the highest number of retained X-Y gametologs recorded in eutherians, in addition to novel Y-born and transp...
Santschi EM, Purdy AK, Valberg SJ, Vrotsos PD, Kaese H, Mickelson JR.Overo lethal white syndrome (OLWS) is an inherited syndrome of foals born to American Paint Horse parents of the overo coat-pattern lineage. Affected foals are totally or almost totally white and die within days from complications due to intestinal aganglionosis. Related conditions occur in humans and rodents in which mutations in the endothelin receptor B (EDNRB) gene are responsible. EDNRB is known to be involved in the developmental regulation of neural crest cells that become enteric ganglia and melanocytes. In this report we identify a polymorphism in the equine EDNRB gene closely associa...
Doan R, Cohen N, Harrington J, Veazey K, Juras R, Cothran G, McCue ME, Skow L, Dindot SV.Copy number variants (CNVs) represent a substantial source of genetic variation in mammals. However, the occurrence of CNVs in horses and their subsequent impact on phenotypic variation is unknown. We performed a study to identify CNVs in 16 horses representing 15 distinct breeds (Equus caballus) and an individual gray donkey (Equus asinus) using a whole-exome tiling array and the array comparative genomic hybridization methodology. We identified 2368 CNVs ranging in size from 197 bp to 3.5 Mb. Merging identical CNVs from each animal yielded 775 CNV regions (CNVRs), involving 1707 protein- and...
Gurgul A, Jasielczuk I, Semik-Gurgul E, Pawlina-Tyszko K, Stefaniuk-Szmukier M, Szmatoła T, Polak G, Tomczyk-Wrona I, Bugno-Poniewierska M.The genetic differentiation of the current horse population was evolutionarily created by natural or artificial selection which shaped the genomes of individual breeds in several unique ways. The availability of high throughput genotyping methods created the opportunity to study this genetic variation on a genome-wide level allowing detection of genome regions divergently selected between separate breeds as well as among different horse types sharing similar phenotypic features. In this study, we used the population differentiation index (FST) that is generally used for measuring locus-specifi...
Wallner B, Palmieri N, Vogl C, Rigler D, Bozlak E, Druml T, Jagannathan V, Leeb T, Fries R, Tetens J, Thaller G, Metzger J, Distl O, Lindgren G....The Y chromosome directly reflects male genealogies, but the extremely low Y chromosome sequence diversity in horses has prevented the reconstruction of stallion genealogies [1, 2]. Here, we resolve the first Y chromosome genealogy of modern horses by screening 1.46 Mb of the male-specific region of the Y chromosome (MSY) in 52 horses from 21 breeds. Based on highly accurate pedigree data, we estimated the de novo mutation rate of the horse MSY and showed that various modern horse Y chromosome lineages split much later than the domestication of the species. Apart from few private northern Euro...
Davila MP, Muñoz PM, Bolaños JM, Stout TA, Gadella BM, Tapia JA, da Silva CB, Ferrusola CO, Peña FJ.To investigate the hypothesis that oxidative phosphorylation is a major source of ATP to fuel stallion sperm motility, oxidative phosphorylation was suppressed using the mitochondrial uncouplers CCCP and 2,4,-dinitrophenol (DNP) and by inhibiting mitochondrial respiration at complex IV using sodium cyanide or at the level of ATP synthase using oligomycin-A. As mitochondrial dysfunction may also lead to oxidative stress, production of reactive oxygen species was monitored simultaneously. All inhibitors reduced ATP content, but oligomycin-A did so most profoundly. Oligomycin-A and CCCP also sign...
Bower MA, McGivney BA, Campana MG, Gu J, Andersson LS, Barrett E, Davis CR, Mikko S, Stock F, Voronkova V, Bradley DG, Fahey AG, Lindgren G....Selective breeding for speed in the racehorse has resulted in an unusually high frequency of the C-variant (g.66493737C/T) at the myostatin gene (MSTN) in cohorts of the Thoroughbred horse population that are best suited to sprint racing. Here we show using a combination of molecular- and pedigree-based approaches in 593 horses from 22 Eurasian and North-American horse populations, museum specimens from 12 historically important Thoroughbred stallions (b.1764-1930), 330 elite-performing modern Thoroughbreds and 42 samples from three other equid species that the T-allele was ancestral and there...
Frank N, Elliott SB, Brandt LE, Keisler DH.To compare obese horses with insulin resistance (IR) with nonobese horses and determine whether blood resting glucose, insulin, leptin, and lipid concentrations differed between groups and were correlated with combined glucose-insulin test (CGIT) results. Methods: 7 obese adult horses with IR (OB-IR group) and 5 nonobese mares. Methods: Physical measurements were taken, and blood samples were collected after horses had acclimated to the hospital for 3 days. Response to insulin was assessed by use of the CGIT, and maintenance of plasma glucose concentrations greater than the preinjection value ...
Rathi R, Colenbrander B, Bevers MM, Gadella BM.The primary aim of this study was to establish a flow cytometric technique for determining the capacitation status of stallion spermatozoa. To this end, a flow cytometric technique that demonstrates changes in plasma membrane fluidity; namely, merocyanine 540 staining, was compared with the more conventional Ca(2+)-dependent fluorescence microscopic technique, chlortetracycline (CTC) staining, for assessing capacitation status. In addition, the effect of bicarbonate/CO(2) on the progress of capacitation and the acrosome reaction (AR) and on temporal changes in sperm motility, with particular r...
Edwards JE, Shetty SA, van den Berg P, Burden F, van Doorn DA, Pellikaan WF, Dijkstra J, Smidt H.Equine gut microbiology studies to date have primarily focused on horses and ponies, which represent only one of the eight extant equine species. This is despite asses and mules comprising almost half of the world's domesticated equines, and donkeys being superior to horses/ponies in their ability to degrade dietary fiber. Limited attention has also been given to commensal anaerobic fungi and archaea even though anaerobic fungi are potent fiber degrading organisms, the activity of which is enhanced by methanogenic archaea. Therefore, the objective of this study was to broaden the current knowl...
