Phenotype in horses refers to the observable physical and behavioral traits of an individual horse, which result from the interaction of its genetic makeup and environmental influences. These traits include characteristics such as coat color, height, conformation, and temperament. Phenotypic expression is a focal point in equine breeding and management, as it influences performance, health, and suitability for specific disciplines. Research in this area examines the genetic basis of phenotypic traits, the impact of environmental factors, and the interaction between genetics and environment. This page aggregates peer-reviewed research studies and scholarly articles that explore the genetic determinants, environmental effects, and practical implications of phenotypic traits in horses.
Lopez BS, Hurley DJ, Giancola S, Giguère S, Felippe MJB, Hart KA.The impact of culture conditions on equine monocyte-derived dendritic cells (MoDC) generation has not been fully characterized. We hypothesized that 1) MoDC could be cultured in a commercially available serum-free medium (AIM-V); and 2) that differential culture conditions would influence MoDC viability, yield and phenotype. MoDC generated from adult horses were cultured under variable conditions in a series of experiments. Viability was assessed using trypan blue and propidium iodide staining. Yield was determined by manual hemocytometer counting. Phenotype was assessed by flow cytometric ana...
Ghosh S, Davis BW, Rosengren M, Jevit MJ, Castaneda C, Arnold C, Jaxheimer J, Love CC, Varner DD, Lindgren G, Wade CM, Raudsepp T.Disorders of sex development (DSD) and reproduction are not uncommon among horses, though knowledge about their molecular causes is sparse. Here we characterized a ~200 kb homozygous deletion in chromosome 29 at 29.7-29.9 Mb. The region contains genes which function as ketosteroid reductases in steroid hormone biosynthesis, including androgens and estrogens. Mutations in genes are associated with human DSDs. Deletion boundaries, sequence properties and gene content were studied by PCR and whole genome sequencing of select deletion homozygotes and control animals. Deletion analysis by PCR in ...
Graves KT, Eberth JE, Bailey E.Homozygous and compound heterozygous Miniature horses for ACAN alleles D1, D2, D3* and D4 exhibit chondrodysplastic dwarfism (OMIA 001271-9796). In a previous study, the carrier rate for these four alleles, combined, was 26.2%. The purpose of this study was to investigate whether carriers of these dwarfism-causing alleles had a shorter withers height than non-carriers. A total of 245 Miniature horses were tested for these four ACAN alleles and also were measured for withers height. Of these horses, 98 were carriers and 147 were non-carriers. A statistically significant difference of 1.43 inche...
Han H, McGivney BA, Farries G, Katz LM, MacHugh DE, Randhawa IAS, Hill EW.Thoroughbred horse racing is a global sport with major hubs in Europe, North America, Australasia and Japan. Regional preferences for certain traits have resulted in phenotypic variation that may result from adaptation to the local racing ecosystem. Here, we test the hypothesis that genes selected for regional phenotypic variation may be identified by analysis of selection signatures in pan-genomic SNP genotype data. Comparing Australian to non-Australian Thoroughbred horses (n = 99), the most highly differentiated loci in a composite selection signals (CSS) analysis were on ECA6 (34.75-34.85 ...
Wilson ME, McCandless EE, Olszewski MA, Robinson NE.Because the alveolar macrophage (AM) phenotype of horses with severe equine asthma (SEA) is unknown, the cytokines expressed by M1- and M2-polarized AM were determined and the hypothesis that natural hay/straw challenge (NC) induces divergent AM phenotypes in control horses and horses with SEA was tested. Macrophages from control horses were activated either with eIFNγ + lipolysaccharide (LPS) or eIL-4 to characterize M1- or M2-polarized AM gene expression, respectively and determine the response of polarized cells to pathogen-associated molecular patterns (PAMPS): LPS, zymosan, peptidoglycan...
Reproductive traits have a major influence on the economic effectiveness of horse breeding. However, there is little information available. We evaluated the use of reproductive traits as selection criteria in official breeding programs to increase the reproductive efficiency of breeding studs, analysing 696 690 records from the pedigree data of eight Spanish horse populations, with different breeding purposes. The reproductive parameters studied in both sexes were age at first foaling (AFF), age at last foaling, average reproductive life and generational interval. In the females, the average ...
Grilz-Seger G, Reiter S, Neuditschko M, Wallner B, Rieder S, Leeb T, Jagannathan V, Mesarič M, Cotman M, Pausch H, Lindgren G, Velie B, Horna M....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...
Villagomez DAF, Welsford EG, King WA, Revay T.In the domestic horse; failure of normal masculinization and virilization due to deficiency of androgenic action leads to a specific disorder of sexual development known as equine androgen insensitivity syndrome (AIS). Affected individuals appear to demonstrate an incoherency between their genetic sex and sexual phenotype; i.e., XY-sex chromosome constitution and female phenotypic appearance. AIS is well documented in humans. Here we report the finding of two novel genetic variants for the AR-gene identified in a Tennessee Walking Horse and a Thoroughbred horse mare; each in individual clinica...
Affolter VK, Dalley B, Kass PH, Brown EA, Sonder C, Bannasch DL.Chronic progressive lymphoedema (CPL) is a disabling condition affecting various draft horse breeds, including Friesian horses. Objective: The high incidence of CPL in Friesian horses suggests a genetic component and a predisposing phenotype. Methods: For the genomic study, 26 affected and 19 control horses were evaluated. Body measurements were taken from 28 affected and nine control Friesian horses. Methods: Axiom® Equine Genotyping Array with a total of 307,474 single nucleotide polymorphism (SNPs) was used for the case/control genome-wide association study (GWAS). Height, weight and leg m...
Andrade DGA, Basso RM, Castiglioni MCR, Silva JP, Machado VMV, Laufer-Amorim R, Borges AS, Oliveira-Filho JP.Four causative mutations (D1, D2, D3*, and D4) of chondrodysplastic dwarfism have been described in the equine () gene. Homozygotes for one of these mutations and heterozygotes for any combination of these mutations exhibit the disproportionate dwarfism phenotype. However, no case description of homozygotes for D4 (D4/D4) has been reported in the literature, to our knowledge. We report 2 Miniature horses with the genotype D4/D4 in the gene. Clinically, the 2 dwarfs had a domed head that was large compared to the rest of the body, mandibular prognathism, and short and bowed limbs, mainly in t...
Durgam SS, Altmann NN, Coughlin HE, Rollins A, Hostnik LD.There is increased incidence of tendon disorders and decreased tendon healing capacity in people with diabetes mellitus (DM). Recent studies have also suggested pathological ossification in repair tendon of people with DM. Therefore, the objective of this study is to investigate the effects of insulin supplementation, an important pathophysiologic stimulus of DM, on tendon progenitor cell (TPC) proliferation and in vitro osteogenic capacity. Passage 3 TPCs were isolated from collagenase-digested, equine superficial digital flexor tendons. TPC proliferation was measured via MTT assay after 3 da...
Fowden AL, Giussani DA, Forhead AJ.In many species, the pattern of growth and physiological development in utero has an important role in determining not only neonatal viability but also adult phenotype and disease susceptibility. Changes in fetal development induced by a range of environmental factors including maternal nutrition, disease, placental insufficiency and social stresses have all been shown to induce adult cardiovascular and metabolic dysfunction that often lead to ill health in later life. Compared to other precocious animals, much less is known about the physiological development of the fetal horse or the longer-...
Bourebaba L, Michalak I, Baouche M, Kucharczyk K, Marycz K.Chondrogenesis represents a highly dynamic cellular process that leads to the establishment of various types of cartilage. However, when stress-related injuries occur, a rapid and efficient regeneration of the tissues is necessary to maintain cartilage integrity. Mesenchymal stem cells (MSCs) are known to exhibit high capacity for self-renewal and pluripotency effects, and thus play a pivotal role in the repair and regeneration of damaged cartilage. On the other hand, the influence of certain pathological conditions such as metabolic disorders on MSCs can seriously impair their regenerative pr...
Farries G, Bryan K, McGivney CL, McGettigan PA, Gough KF, Browne JA, MacHugh DE, Katz LM, Hill EW.While over ten thousand genetic loci have been associated with phenotypic traits and inherited diseases in genome-wide association studies, in most cases only a relatively small proportion of the trait heritability is explained and biological mechanisms underpinning these traits have not been clearly identified. Expression quantitative trait loci (eQTL) are subsets of genomic loci shown experimentally to influence gene expression. Since gene expression is one of the primary determinants of phenotype, the identification of eQTL may reveal biologically relevant loci and provide functional links ...
Srikanth K, Kim NY, Park W, Kim JM, Kim KD, Lee KT, Son JH, Chai HH, Choi JW, Jang GW, Kim H, Ryu YC, Nam JW, Park JE, Kim JM, Lim D.The Jeju horse, indigenous to the Jeju Island in Korea may have originated from Mongolian horses. Adaptations to the local harsh environment have conferred Jeju horse with unique traits such as small-sized body, stocky head, and shorter limbs. These characteristics have not been studied previously at the genomic level. Therefore, we sequenced and compared the genome of 41 horses belonging to 6 breeds. We identified numerous breed-specific non-synonymous SNPs and loss-of-function mutants. Demographic and admixture analyses showed that, though Jeju horse is genetically the closest to the Mongol...
De Angelis E, Cacchioli A, Ravanetti F, Bileti R, Cavalli V, Martelli P, Borghetti P.Chondrocyte dedifferentiation is a key limitation in therapies based on autologous chondrocyte implantation for cartilage repair. Articular chondrocytes, obtained from (metacarpophalangeal and metatarsophalangeal) joints of different aged horses, were cultured in monolayer for several passages (P0 to P8). Cumulative Populations Doublings Levels (PDL) and gene expression of relevant chondrocyte phenotypic markers were analysed during culturing. Overall data confirmed that, during proliferation in vitro, horse chondrocytes undergo marked morphological and phenotypic alterations of their differen...
Norton E, Schultz N, Geor R, McFarlane D, Mickelson J, McCue M.Equine metabolic syndrome (EMS) is a complex trait for which few genetic studies have been published. Our study objectives were to perform within breed genome-wide association analyses (GWA) to identify associated loci in two high-risk breeds, coupled with meta-analysis to identify shared and unique loci between breeds. GWA for 12 EMS traits identified 303 and 142 associated genomic regions in 264 Welsh ponies and 286 Morgan horses, respectively. Meta-analysis demonstrated that 65 GWA regions were shared across breeds. Region boundaries were defined based on a fixed-size or the breakdown of li...
Solé M, Ablondi M, Binzer-Panchal A, Velie BD, Hollfelder N, Buys N, Ducro BJ, François L, Janssens S, Schurink A, Viklund Å, Eriksson S....Copy Number Variation (CNV) is a common form of genetic variation underlying animal evolution and phenotypic diversity across a wide range of species. In the mammalian genome, high frequency of CNV differentiation between breeds may be candidates for population-specific selection. However, CNV differentiation, selection and its population genetics have been poorly explored in horses. Results: We investigated the patterns, population variation and gene annotation of CNV using the Axiom® Equine Genotyping Array (670,796 SNPs) from a large cohort of individuals (N = 1755) belonging to eight ...
Tanaka J, Leeb T, Rushton J, Famula TR, Mack M, Jagannathan V, Flury C, Bachmann I, Eberth J, McDonnell SM, Penedo MCT, Bellone RR.Mushroom is a unique coat color phenotype in Shetland Ponies characterized by the dilution of the chestnut coat color to a sepia tone and is hypothesized to be a recessive trait. A genome wide association study (GWAS), utilizing the Affymetrix 670K array (MNEc670k) and a single locus mixed linear model analysis (EMMAX), identified a locus on ECA7 for further investigation ( = 2.08 × 10). This locus contained a 3 Mb run of homozygosity in the 12 mushroom ponies tested. Analysis of high throughput Illumina sequencing data from one mushroom Shetland pony compared to 87 genomes from horses of var...
Hybridization has been widely practiced in plant and animal breeding as a means to enhance the quality and fitness of the organisms. In domestic equids, this hybrid vigor takes the form of improved physical and physiological characteristics, notably for strength or endurance. Because the offspring of horse and donkey is generally sterile, this widely recognized vigor is expressed in the first generation (F1). However, in the absence of recombination between the two parental genomes, F1 hybrids can be expected to be phenotypically intermediate between their parents which could potentially restr...
Turlo AJ, Mueller-Breckenridge AJ, Zamboulis DE, Tew SR, Canty-Laird EG, Clegg PD.The main challenge in tendon injury management is suboptimal tissue healing that fails to re-establish original tendon function. Tissue bioengineering is a promising approach for tendon therapy, with potential to improve its functional outcomes. However, evaluation criteria for tissue-engineered tendon are unclear due to the lack of specific markers of differentiated tendon. The study aim was to identify a panel of genes that characterised tendons in comparison to cartilage or muscles and validate those genes, both in human and key species used as models for tendon diseases. Gene expression pr...
Velie BD, Smith PM, Fjordbakk CT, Solé M, Jäderkvist Fegraeus K, Rosengren MK, Røed KH, Ihler CF, Lindgren G, Strand E.Dynamic laryngeal collapse (DLC) associated with poll flexion is the most common disorder of the upper respiratory tract (URT) in the Norwegian-Swedish Coldblooded Trotter (NSCT). The disorder, which has also been diagnosed in other breeds of trotters and gaited horses, appears to be related to anatomic phenotypes and only occurs during poll flexion when the horse is exercised 'on the bit'. Objective: Identify genomic regions associated with DLC in the NSCT by combining a rigorous phenotyping protocol with genomic data from a high-density equine genotyping array. Methods: Prospective case/cont...
Farries G, Gough KF, Parnell AC, McGivney BA, McGivney CL, McGettigan PA, MacHugh DE, Katz LM, Hill EW.Despite strong selection for athletic traits in Thoroughbred horses, there is marked variation in speed and aptitude for racing performance within the breed. Using global positioning system monitoring during exercise training, we measured speed variables and temporal changes in speed with age to derive phenotypes for GWAS. The aim of the study was to test the hypothesis that genetic variation contributes to variation in end-point physiological traits, in this case galloping speed measured during field exercise tests. Standardisation of field-measured phenotypes was attempted by assessing horse...
Ropka-Molik K, Stefaniuk-Szmukier M, Musiał AD, Velie BD.Arabian horses are commonly believed to be one of the oldest and most influential horse breeds in the world. The high financial benefits obtained from races tend to search for genetic markers strongly correlated with the results achieved. To date, the modern approaches such as transcriptome, miRNAome, and metabolome analyses have been used to investigate the genetic background of racing performance as well as endurance capacity in Arabians. The analysis of polymorphisms at the genome level has also been applied to the detection of genetic variants associated with exercise phenotype in the Arab...
Lewczuk D, Metera-Zarzycka E.Many horse breeds in the world are reserved as genetic resources; however, their characteristics seem to be insufficiently clarified, especially in terms of horse performance. Two jumping ability evaluation methods have been used to compare different types of performance breeds and on this basis their applicability for precision phenotyping has been determined. Methods: Jumping data of 186 young Polish Warmblood stallions (27 with an endangered status) bred for sport and multipurpose use was collected during their performance tests organised under identical environmental conditions following t...
François L, Hoskens H, Velie BD, Stinckens A, Tinel S, Lamberigts C, Peeters L, Savelkoul HFJ, Tijhaar E, Lindgren G, Janssens S, Ducro BJ, Buys N....Insect bite hypersensitivity (IBH), which is a cutaneous allergic reaction to antigens from Culicoides spp., is the most prevalent skin disorder in horses. Misdiagnosis is possible, as IBH is usually diagnosed based on clinical signs. Our study is the first to employ IgE levels against several recombinant Culicoides spp. allergens as an objective, independent, and quantitative phenotype to improve the power to detect genetic variants that underlie IBH. Genotypes of 200 Shetland ponies, 127 Icelandic horses, and 223 Belgian Warmblood horses were analyzed while using a mixed model approach. No s...
Musiał AD, Ropka-Molik K, Piórkowska K, Jaworska J, Stefaniuk-Szmukier M.In horses, the identification of the genetic background of phenotypic variation, especially with regard to performance characteristics and predisposition to effort, has been extensively studied. As α-actinin-3 function is related to the regulation of muscle contraction and cell metabolism, the ACTN3 gene is considered one of the main genetic factors determining muscle strength. The aim of the present study was to assess the genotype distribution of two SNP variants within the equine ACTN3 gene (g.1104G > A and c.2334C > T) across different utility types and horse breeds. The ana...
Fawcett JA, Sato F, Sakamoto T, Iwasaki WM, Tozaki T, Innan H.The domestication process of plants and animals typically involves intense inbreeding and directional selection for various traits. Here, we genotyped 370 Japanese Thoroughbred horses using the recently developed 670k SNP array and performed various genome-wide analysis also using genotype data of other horse breeds. We identified a number of regions showing interesting patterns of polymorphisms. For instance, the region containing the MC1R locus associated with chestnut coat color may have been targeted by selection for a different mutation much earlier on than the recent selection for chestn...
De Angelis E, Cacchioli A, Ravanetti F, Bileti R, Cavalli V, Martelli P, Borghetti P.Chondrocyte dedifferentiation is a key limitation in therapies based on autologous chondrocyte implantation for cartilage repair. Articular chondrocytes, obtained from (metacarpophalangeal and metatarsophalangeal) joints of different aged horses, were cultured in monolayer for several passages (P0 to P8). Cumulative Populations Doublings Levels (PDL) and gene expression of relevant chondrocyte phenotypic markers were analysed during culturing. Overall data confirmed that, during proliferation in vitro, horse chondrocytes undergo marked morphological and phenotypic alterations of their differen...
Mawdsley A, Kelly EP, Smith FH, Brophy PO.A linear assessment trait evaluation system is proposed to allow quantitative description of the static conformation of the horse. Measurements were made on 27 selected traits. The system was tested initially for repeatability of measurements on 4 horses. Twenty-one of the selected traits were satisfactory and 6 proved unsatisfactory in terms of reproducibility. A population of 101, superior 2- and 3-year-old Thoroughbreds and 19 premium Thoroughbred stallions were similarly assessed. More than 65% of the traits exhibited large (CV > 10%) phenotypic variation within the sampled population. ...
Go YY, Cook RF, Fulgêncio JQ, Campos JR, Henney P, Timoney PJ, Horohov DW, Balasuriya UB.In a recent study, we demonstrated that the virulent Bucyrus strain (VBS) of EAV could infect in vitro a small population of CD3(+) T lymphocytes from some but not all horses. Furthermore, we have shown that a common haplotype is associated with this in vitro CD3(+) T cell susceptibility/resistance phenotype to EAV infection. In this study, we investigated whether the differences in the susceptibility or resistance of CD3(+) T cells in vitro correlate with the outcome and severity of clinical signs in vivo. Thus, horses were divided into two groups based on their CD3(+) T cell susceptible or r...
Grilz-Seger G, Reiter S, Neuditschko M, Wallner B, Rieder S, Leeb T, Jagannathan V, Mesarič M, Cotman M, Pausch H, Lindgren G, Velie B, Horna M....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...
Reissmann M, Musa L, Zakizadeh S, Ludwig A.Considering the hidden mode of inheritance of some coat-color-associated alleles, we investigated the presence/absence of coat-color-associated alleles in 1093 domestic horses of 55 breeds and 20 specimens of Przewalski's horse. For coat-color genotyping, allele specific PCR, pyrosequencing and Li-Cor analyses were conducted on 12 coat-color-associated alleles of five genes. Our data provide deep insight into the distribution of coat-color-associated alleles within breeds. We found that the alleles for the basic colorations (bay, black, and chestnut) are widely distributed and occur in nearly ...
Sandoval-Castellanos E, Wutke S, Gonzalez-Salazar C, Ludwig A.Wild horses unexpectedly survived terminal Pleistocene megafaunal extinctions until eventual European extirpation in the twentieth century. This survival is tied to either their occurrence in cryptic open habitats or their adaptation to forests. Our niche modelling inferred an increasing presence of horses in post-glacial forests, and our analysis of ancient DNA suggested significant selection for black phenotypes as indicating adaptation to forests.
Bourebaba L, Michalak I, Baouche M, Kucharczyk K, Marycz K.Chondrogenesis represents a highly dynamic cellular process that leads to the establishment of various types of cartilage. However, when stress-related injuries occur, a rapid and efficient regeneration of the tissues is necessary to maintain cartilage integrity. Mesenchymal stem cells (MSCs) are known to exhibit high capacity for self-renewal and pluripotency effects, and thus play a pivotal role in the repair and regeneration of damaged cartilage. On the other hand, the influence of certain pathological conditions such as metabolic disorders on MSCs can seriously impair their regenerative pr...
Gold S, Regan CE, McLoughlin PD, Gilleard JS, Wilson AJ, Poissant J.Variability in host resistance or tolerance to parasites is nearly ubiquitous, and is of key significance in understanding the evolutionary processes shaping host-parasite interactions. While ample research has been conducted on the genetics of parasite burden in livestock, relatively little has been done in free-living populations. Here, we investigate the sources of (co)variation in strongyle nematode faecal egg count (FEC) and body condition in Sable Island horses, a feral population in which parasite burden has previously been shown to negatively correlate with body condition. We used the ...
Mirams M, Tatarczuch L, Ahmed YA, Pagel CN, Jeffcott LB, Davies HM, Mackie EJ.Osteochondrosis is a condition involving defective endochondral ossification and retention of cartilage in subchondral bone. The pathophysiology of this condition is poorly characterized, but it has been proposed that the fundamental defect is failure of chondrocyte hypertrophy. The aim of the current study was to characterize phenotypic changes in chondrocytes associated with the initiation of osteochondrosis. Early lesions were induced in an equine model of osteochondrosis by feeding foals a high energy diet for 8 or 15 weeks. Lesions in articular-epiphyseal growth cartilage were examined hi...
Christensen H, Bisgaard M, Angen O, Olsen JE.Phenotypic characterization of bacteria from diseased and healthy horses identified 18 isolates as Bisgaard taxon 9 and 11 isolates as Actinobacillus lignieresii. All strains of taxon 9 were alpha-galactosidase- and raffinose-positive and showed variable fermentation of (+)L-arabinose and (-)D-sorbitol. Strains of A. lignieresii were negative for these characteristics, with the exception of raffinose. Two strains from the (-)D-sorbitol-negative group of taxon 9 showed a 16S rRNA similarity of 99-6%, while 99.5% similarity was found between two strains of the (-)D-sorbitol-positive group. DNA-D...
Negro S, Imsland F, Valera M, Molina A, Solé M, Andersson L.Several variants in the KIT, PAX3 and MITF genes have previously been associated with white markings in horses. In this study, we examined eight variants of these genes in 70 Menorca Purebred horses (PRMe, only black solid-coloured horses) and 70 Spanish Purebred horses (PRE, different coat colour patterns) that were scored for the extent of white markings. A maximum-likelihood chi-square test, logistic regression model and ridge regression analyses showed that a missense mutation (p.Arg682His) in KIT was associated with white facial markings (P < 0.05) and with total white markings (P &...
Wilson ME, McCandless EE, Olszewski MA, Robinson NE.Because the alveolar macrophage (AM) phenotype of horses with severe equine asthma (SEA) is unknown, the cytokines expressed by M1- and M2-polarized AM were determined and the hypothesis that natural hay/straw challenge (NC) induces divergent AM phenotypes in control horses and horses with SEA was tested. Macrophages from control horses were activated either with eIFNγ + lipolysaccharide (LPS) or eIL-4 to characterize M1- or M2-polarized AM gene expression, respectively and determine the response of polarized cells to pathogen-associated molecular patterns (PAMPS): LPS, zymosan, peptidoglycan...
Britz E, Spier SJ, Kass PH, Edman JM, Foley JE.Equine infection with Corynebacterium pseudotuberculosis can manifest in several forms, including external or internal abscesses. The objective of this study was to phenotype clinical isolates of C. pseudotuberculosis and to investigate the relationship between lesion location and extent of lesions in the animals from which they were collected. One hundred and seventy-one C. pseudotuberculosis biovar equi isolates were collected from horses presenting to the University of California Veterinary Medical Teaching Hospital and two other sources in the period between September 1996 and December 201...
Voß K, Blaj I, Tetens JL, Thaller G, Becker D.Since domestication, a wide variety of phenotypes including coat color variation has developed in livestock. This variation is mostly based on selective breeding. During the beginning of selective breeding, potential negative consequences did not become immediately evident due to low frequencies of homozygous animals and have been occasionally neglected. However, numerous studies of coat color genetics have been carried out over more than a century and, meanwhile, pleiotropic effects for several coat color genes, including disorders of even lethal impact, were described. Similar coat color phe...
Costa GMJ, Avelar GF, Lacerda SMSN, Figueiredo AFA, Tavares AO, Rezende-Neto JV, Martins FGP, França LR.The establishment of proper conditions for spermatogonial stem cells (SSCs) cryopreservation and storage represents an important biotechnological approach for the preservation of the genetic stock of valuable animals. This study demonstrates the effects of different cryopreservation protocols on the survival rates and phenotypic expression of SSCs in horses. The cells were enzymatically isolated from testes of eight adult horses. After enrichment and characterization of germ cells in the suspension, the feasibility of several cryopreservation protocols were evaluated. Three different cryomedia...
Laseca N, Molina A, Valera M, Antonini A, Demyda-Peyrás S.Copy number variations (CNVs) are a new-fangled source of genetic variation that can explain changes in the phenotypes in complex traits and diseases. In recent years, their study has increased in many livestock populations. However, the study and characterization of CNVs in equines is still very limited. Our study aimed to investigate the distribution pattern of CNVs, characterize CNV regions (CNVRs), and identify the biological pathways affected by CNVRs in the Pura Raza Española (PRE) breed. To achieve this, we analyzed high-density SNP genotyping data (670,804 markers) from a large cohort...
Farries G, McGettigan PA, Gough KF, McGivney BA, MacHugh DE, Katz LM, Hill EW.Adaptation to early training and racing (i.e. precocity), which is highly variable in racing Thoroughbreds, has implications for the selection and training of horses. We hypothesised that precocity in Thoroughbred racehorses is heritable. Age at first sprint training session (work day), age at first race and age at best race were used as phenotypes to quantify precocity. Using high-density SNP array data, additive SNP heritability (hSNP2) was estimated to be 0.17, 0.14 and 0.17 for the three traits respectively. In genome-wide association studies (GWAS) for age at first race and age at best ra...
Garvican ER, Vaughan-Thomas A, Redmond C, Clegg PD.Our objective was to characterize the variation in gene expression for key genes associated with chondrogenic phenotype of osteochondrosis (OC)-affected and normal chondrocytes, and to identify whether OC chondrocytes can redifferentiate and regain a phenotype similar to normal chondrocytes if appropriate chondrogenic signals are given. Equine articular cartilage removed at surgery to treat clinically significant OC lesions was collected (n = 10), and the gene expression evaluated and compared to aged-matched normal samples (n = 10). Cartilage was harvested from normal (n = 4) and OC (n = 3) j...
Knickelbein KE, Lassaline ME, Singer-Berk M, Reilly CM, Clode AB, Famula TR, Michau TM, Bellone RR.Belgian horses are commonly affected with ocular squamous cell carcinoma (SCC), the most common cancer of the equine eye. A missense mutation in damage-specific DNA binding protein 2 (DDB2 c.1013C>T, p.Thr338Met) has been established as a recessive genetic risk factor for ocular SCC in the Haflinger breed. A sample of Belgian horses with unknown SCC phenotype was shown to possess this variant at a similar frequency to the Haflinger breed. Retrospective studies indicate that chestnut coat colour may predispose to the development of SCC. Objective: To determine if DDB2 c.1013C>T is a risk ...
Marsh AE, Johnson PJ, Ramos-Vara J, Johnson GC.Little information is available about antigenic variation of Sarcocystis neurona isolated from horses with equine protozoal myeloencephalitis, nor is there much information available on the specific antibody pattern to S. neurona antigens of horses from different geographic regions where S. neurona isolates have been obtained. This communication reports on the characterization of a new S. neurona isolate, SN-MU1. The isolate was obtained from a 3-year old Thoroughbred that had asymmetrical neurological signs and localized skeletal muscle atrophy. This S. neurona isolate is similar to other S. ...
Patterson Rosa L, Martin K, Vierra M, Foster G, Lundquist E, Brooks SA, Lafayette C.Over 30 polymorphisms in the KIT Proto-Oncogene Receptor Tyrosine Kinase (KIT) gene have been implicated in white spotting patterns ranging from small areas to full dermal depigmentation in the horse. We performed a candidate-gene exon sequencing approach on KIT and MITF, 2 known causatives of white spotting patterns, within 2 families of horses of unknown white spotting. Family 1 (Fam1, N = 5) consisted of a Quarter Horse stallion and 4 offspring with white spotting pattern ranging from legs, lower ventral, and head regions with jagged borders, to almost complete white. The second family (Fam...
Górecka A, Słoniewski K, Golonka M, Jaworski Z, Jezierski T.There are studies on the relationship between the position and shape of hair whorls on bovine forehead and phenotypic traits. According to anecdotal beliefs by horse users and handlers, temperamental traits may be related to the position of hair whorls in horses. No previous research on the mechanisms of inheritance of hair whorls has been performed, so the aim of the present study was to determine the heritability of the position of the hair whorl on the forehead of Konik horses. The horses (n = 362) were classified into five groups based on the whorl position on forehead with respect to the ...
Ewart SL, Ramsey DT, Xu J, Meyers D.Anterior segment dysgenesis syndrome occurs frequently in Rocky Mountain horses and has two distinct ocular phenotypes: (1) large cysts originating from the temporal ciliary body or peripheral retina and (2) multiple anterior segment anomalies including ciliary cysts, iris hypoplasia, iridocorneal adhesions and opacification, nuclear cataract, and megalocornea. To determine if anterior segment dysgenesis syndrome is heritable in horses we performed ophthalmic examinations and collected pedigree information on horses (n = 516) in an extended Rocky Mountain horse pedigree. Logistic regressive se...
Finno CJ, Stevens C, Young A, Affolter V, Joshi NA, Ramsay S, Bannasch DL.Horses belong to the order Perissodactyla and bear the majority of their weight on their third toe; therefore, tremendous force is applied to each hoof. An inherited disease characterized by a phenotype restricted to the dorsal hoof wall was identified in the Connemara pony. Hoof wall separation disease (HWSD) manifests clinically as separation of the dorsal hoof wall along the weight-bearing surface of the hoof during the first year of life. Parents of affected ponies appeared clinically normal, suggesting an autosomal recessive mode of inheritance. A case-control allelic genome wide associat...
Kuhnert P, Korczak B, Falsen E, Straub R, Hoops A, Boerlin P, Frey J, Mutters R.Gram-negative, nonmotile bacteria that are catalase, oxidase, and urease positive are regularly isolated from the airways of horses with clinical signs of respiratory disease. On the basis of the findings by a polyphasic approach, we propose that these strains be classified as Nicoletella semolina gen. nov, sp. nov., a new member of the family Pasteurellaceae. N. semolina reduces nitrate to nitrite but is otherwise biochemically inert; this includes the lack of an ability to ferment glucose and other sugars. Growth is fastidious, and the isolates have a distinctive colony morphology, with the ...
Cothran EG, MacCluer JW, Weitkamp LR, Bailey E.American Standardbred horses are divided into two groups based upon gait: the trot and the pace. The tendency to trot (diagonally opposite legs moving forward together) or pace (the two legs on the same side of the body moving forward together) appears to be genetically determined, although no formal genetic analysis has been undertaken. There is nearly complete assortative mating for gait; however, about 20% of the offspring sired by trotters are registered as pacers, while fewer than 1% of those sired by pacers are registered as trotters. Electrophoretically detectable genic variation at 13 ...
Durward-Akhurst SA, Marlowe JL, Schaefer RJ, Springer K, Grantham B, Carey WK, Bellone RR, Mickelson JR, McCue ME.Disease-causing variants have been identified for less than 20% of suspected equine genetic diseases. Whole genome sequencing (WGS) allows rapid identification of rare disease causal variants. However, interpreting the clinical variant consequence is confounded by the number of predicted deleterious variants that healthy individuals carry (predicted genetic burden). Estimation of the predicted genetic burden and baseline frequencies of known deleterious or phenotype associated variants within and across the major horse breeds have not been performed. We used WGS of 605 horses across 48 breeds ...
Abbott Y, Leonard FC, Markey BK.This study involved the phenotypic and molecular characterization of a population of methicillin-resistant Staphylococcus aureus isolates from animals and from veterinary personnel in Ireland. Isolates from 77 animals (dogs, n=44; cats, n=4; horses, n=29) and from 28 veterinary personnel were characterized using their antimicrobial resistance profiles and pulsed-field gel electrophoresis patterns. In addition, a representative number of these isolates (n=52) were further analysed using spa-typing techniques. The results obtained identified the presence of three distinct clonal complexes, CC5, ...
De La Peña-Moctezuma A, Prescott JF, Goodfellow M.Four isolates of Rhodococcus equi, from pneumonic foals, and containing the 85 kb virulence plasmid, a porcine isolate containing an 80 kb plasmid, and their plasmid cured derivatives, were examined for 239 phenotypic properties in an attempt to find characters other than the virulence-associated protein (VapA) which might be encoded by the virulence plasmid in organisms grown at 37 degrees C. Tests chosen included those which have previously given variable results for R. equi isolates, since such variability might be attributed to plasmid curing, and characteristics which have been described ...
