Heritability in horses refers to the proportion of observable variation in traits among individuals that can be attributed to genetic factors. It is a key concept in understanding how traits such as height, coat color, speed, and temperament are passed from one generation to the next. Heritability estimates help in predicting the potential for selective breeding and the likelihood of certain traits being expressed in offspring. These estimates are calculated using statistical methods that analyze the resemblance between relatives. This page aggregates peer-reviewed research studies and scholarly articles that explore the genetic basis of heritable traits in horses, the methodologies for estimating heritability, and the implications for equine breeding and management practices.
Santana ML, Bignardi AB.Heat stress is an increasingly important challenge for the performance and welfare of equine athletes, particularly in competitions conducted across diverse climatic conditions. Understanding the genetic basis of performance responses to increasing thermal load is therefore essential to support robust genetic evaluation and sustainable selection strategies. The objective of this study was to evaluate barrel racing performance of Brazilian Quarter Horses across thermal environments defined by two widely used indicators, the temperature-humidity index (THI) and the wet bulb globe temperature (WB...
Siemieniuch-Tartanus M, Tomczyk-Wrona I, Tobolski D.Performance testing is a critical tool for achieving genetic progress, yet its long-term effectiveness in primitive breeds under conservation programs is poorly documented. The Konik Polski horse breeding program aims to improve utility while preserving primitive characteristics. Unassigned: This retrospective study analyzed a 25-year longitudinal dataset ( = 1,608) from the official Field Performance Test to quantify genetic trends in gait efficiency, using nonparametric methods to assess the effects of test type, year, and age on stride length and speed at the walk and trot. To estimate he...
Laseca N, Molina A, Ziadi C, Perdomo-Gonzalez DI, Valera M.Conformational traits define a horse's shape and morphology, heavily influencing its functionality, sport performance, health, and appearance, making conformation a critical selection criterion in horse breeding. However, the genomic basis of conformational defects, specifically those affecting the hock, remains largely unexplored. This research aimed to identify the genomic regions associated with hock defects using a large cohort of Pura Raza Española (PRE) horses. A total of 58,930 horses were evaluated for hock angle, with 4,122 genotyped on high or medium density arrays. For this purpose...
Shen Z, Yang L, Xue Y, Chang X, Shen J, Sun W, Zeng Y, Meng J, Yao X.Body measurement traits are key indicators for evaluating growth performance, production potential, and breeding value in Yili horses. However, studies investigating the association between body measurement traits and mutation loci in Yili horses remain limited. In this study, 255 adult Yili mares were used as the study population, including 152 speed-type and 103 meat-type individuals. Whole-genome resequencing was performed, and four phenotypic traits and body weight were measured. A mixed linear model (MLM)-based genome-wide association study (GWAS) was conducted using GEMMA (v 0.98.5), inc...
Pasicka E, Sobek Z, Wierzbicki H, Różańska-Zawieja J, Nienartowicz-Zdrojewska A.The objective of this paper is to demonstrate the morphometric diversity of 172 Polish Koniks from the largest Polish breeding centers and to assess their genetic diversity by estimating the effective population size () and heritabilities () of the studied traits. The animals were bred under a stable housing system. Horses of both sexes aged 3 to 24 years were analyzed. Each horse was characterized with 40 metric traits. Multifactorial analyses (PCA, DA) and the REML method were applied to reveal the exterior differentiation and the development of distinct morphometric types. The findings esta...
Gartland KL, Leśniak K, Twigg-Flesner A.Scientific interest in relation to Fragile Foal Syndrome (FFS) has proliferated in the last decade, but before this, many clinical cases were attributed to other similarly presenting equine neonatal disorders. It was thought that FFS-affected foals were mainly miscarried throughout gestation, but recent study results suggest that often, foals are born alive and die shortly after birth. FFS is proposed to have originated as long ago as the Godolphin Arabian, but the definite derivation of the mutant allele is unconfirmed. The discovery that FFS is present in 11-30% of Warmbloods and 2-3% of Tho...
Lewczuk D, Borowska A, Maśko M, Bagnicka E.: Knowledge of the genetic background of evaluated traits has been the basis for genetic progress in every horse-breeding population and is essential for precise breeding and up-to-date decision-making. The study aimed to estimate the heritability coefficients for field performance traits in mares. : The research was based on 1408 evaluations of mares conducted during the years 2002-2021 in 51 training centers in Poland. The preliminary analyses of the effects, significant for the investigated traits, were obtained using analysis of variance, and these additional data are also presented (SAS p...
Santana ML, Bignardi AB, Faria RAS, Silva JAIV.Thermal load is a major welfare and performance concern for athletic horses, as physical exertion increases internal heat production. Although several phenotypic strategies have been developed to mitigate its effects, the genetic basis of thermal tolerance in horses remains largely unexplored. This study aimed to (1) evaluate the influence of thermal indices on the racing performance of Brazilian Quarter Horses, and (2) investigate the genetic basis of thermal tolerance through the estimation of genetic parameters across temperature gradients. We analyzed 21,857 racing-time (RT) records from 5...
Ricard A, Deretz S, Menard C, Priest BDS.The objective was to evaluate the genetic relationship between the surface temperature of regions of interest, measured using infrared images of young horses and functional longevity in jumping. This relationship was assessed by comparing the temperatures measured in the offspring of two groups of sires, one favourable and one unfavourable, to longevity. The study used a specific data collection protocol on a sample of 921 young progeny, before they began competing, of 141 extreme stallions, comprising 61 favourable and 80 unfavourable sires. These stallions had been selected based on estimate...
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...
Encina A, Sánchez-Guerrero MJ, Ligero M, Rodríguez-Sainz de Los Terreros A, Valera M.White leg markings in horses are phenotypic traits influenced by genetic and environmental factors. This study analyzed their prevalence, symmetry, and genetic parameters in 38,825 Pura Raza Española (PRE) horses registered in the official studbook. White markings were scored using a binary (affected/unaffected) and a four-level ordinal scale. Most horses (38,341 out of 38,825; 98.8%) had at least one limb without white markings. The prevalence of white markings was higher in the hindlegs (17.9% LH; 14.5% RH) than in the forelegs (5.3% LF; 4.6% RF). Markings were most frequent above the fetlo...
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...
Berglund P, Andonov S, Strandberg E, Eriksson S.Harness racing is popular in several parts of the world, and the ability to race barefoot is an important trait for success because of its effect on racing time. Barefoot racing is also discussed in terms of animal welfare because not all horses have hooves that tolerate racing without shoes. In Swedish Standardbred trotters (SB) and Swedish-Norwegian Coldblooded trotters (CB), the proportion of barefoot races and the probability to race barefoot in any given race (barefoot status) have low-to-moderate heritability (h = 0.07-0.28). However, the genetic correlation between the ability to race...
Karlau A, Azcona F, Molina A, Trigo P, Sánchez-Serrano JP, Demyda-Peyrás S.The Peruano de Paso is a horse breed renowned for its smooth gait, traditionally selected based on breeders' empirical knowledge. Recently, the frequency of chestnut horses, a recessive trait, has increased substantially within the official studbook. This study evaluated whether preference for chestnut coat colour has influenced morphological traits and genetic diversity within the breed. A total of 8376 records of seven morphological traits, collected by the Peruano de Paso Breeders Association over eight years, were analysed, along with a pedigree including 41,357 individuals. Morphological ...
Corbally AF, Mulligan FJ, Sweeney T, Fahey AG.This study examines the associations between linearly scored phenotypic traits and auction sales prices of young event horses in Ireland, aiming to identify key traits influencing market value. Data from 307 horses sold at public auctions (2022-2023) were analysed using regression analysis, binary optimisation, and Principal Component Analysis (PCA). Regression identified Head-neck Connection, Quality of Legs, Walk length of Stride, and Scope as highly significant predictors of sales price ( < 0.001), with Length of Croup, Trot Elasticity, Trot Balance, and Take-off Direction also significa...
Gelinder Viklund Å, Blom Y, Eriksson S.The breeding goal of the Swedish Warmblood horse (SWB) is to produce internationally competitive horses in dressage and show jumping. In the current genetic evaluation, breeding values are estimated in multiple-trait animal models where competition performance is the target trait and results from two different young horse tests serve as indicator traits. However, preselection of horses, both for young horse tests and for competitions, is not considered in the current evaluation. The overall aim of this study was to analyse the all-or-none trait start status, in competition and in young horse t...
Donovan K, Torres J, Zhu D, Herrington WG, Staplin N.Genome-wide association studies (GWAS) of disease progression are vulnerable to collider bias caused by selection of participants with disease at study entry. This bias introduces spurious associations between disease progression and genetic variants that are truly only associated with disease incidence. Methods of statistical adjustment to reduce this bias have been published, but rely on assumptions regarding the genetic correlation of disease incidence and disease progression which are likely to be violated in many human diseases. MR-Horse is a recently published Bayesian method to estimate...
Ziadi C, Valera M, Laseca N, Perdomo-González D, Demyda-Peyrás S, de Los Terreros AR, Molina A. By simultaneously integrating both genotyped and non-genotyped animals into genetic evaluation, the single-step genomic BLUP method enhanced the accuracy of genetic assessments. This study aimed to compare the increase in prediction reliability (R) between restricted maximum likelihood (REML) and single-step genomic REML (ssGREML) in the Pura Raza Española (PRE) horse breed. The dataset comprised reproductive records for seven fertility traits from 47,502 females, with a total of 57,316 animals represented in the pedigree. A total of 4009 animals were genotyped using the EQUIGENE 90K SNP ar...
Muñoz-Jurado A, Requena F, Agüera EI, Escribano BM.Anti-Müllerian hormone (AMH) is a dimeric glycoprotein belonging to the superfamily of the transforming growth factor-β. Due to the discovery of AMH functions, relative to the ovarian function, it is being postulated as being a highly important marker in studies on mammalian reproduction. Therefore, the objective of this review was to describe the role of this hormone in different reproductive aspects of female mammals, taking women, cows, and mares as reference species. The relationship between ovarian reserve and AMH was analysed, and it has been verified that there is a relationship betwe...
Yokomori T, Tozaki T, Segawa T, Itou T.Previous studies have examined the relationship between hair characteristics and temperament traits in various animals. A partial genetic association has been suggested in humans because whorl formation and neurological development occur simultaneously during the fetal period. In the horse industry, anecdotal evidence suggests a link between the forehead whorl position and temperament. In our previous study, the heritability of forehead whorl positioning was h=0.653, indicating significant genetic contributions in thoroughbreds. Therefore, in this study, we designed a genome-wide association s...
Santana ML, Franco TGB, Bignardi AB.Barrel racing is a competitive timed rodeo event that challenges horses and riders to complete a cloverleaf pattern around three barrels in the fastest time possible. In this study, we aimed to estimate the genetic parameters of barrel racing time (BRT) and evaluate the most suitable statistical model for its analysis. We compared a repeatability model and three random regression models (RRM) to analyse the longitudinal BRT data in Brazilian Quarter Horses. A total of 356,877 BRT records from 14,108 horses that competed in various events held across Brazil between 2010 and 2024 were analysed. ...
Berglund P, Andonov S, Jansson A, Olsson C, Lundqvist T, Strandberg E, Eriksson S.In equine sports, shoes are used to protect the hooves from wear and tear. In Swedish trotting races, pulling off the shoes to race barefoot is popular because it improves racing time. Good hoof quality is essential for high-performance horses, but not all trotting horses have hooves that tolerate barefoot racing. The ability to race barefoot is a complex trait that is known to be influenced by environmental factors, but the genetic basis of this trait has not been studied. The aim of this study was to estimate genetic parameters and correlations between estimated breeding values for three nov...
Wang C, Zeng Y, Wang J, Wang T, Li X, Shen Z, Meng J, Yao X.The Yili horse is a riding-type breed that has been continuously bred independently in China. The genetics of body conformation and racing performance traits need to be comprehensively considered in making breeding decisions. This study is the first to estimate the genetic parameters of 13 body conformation and racing performance traits in Yili horses using a linear model. In total, 9937 body conformation and 2576 race records of 9100 Yili horses obtained from 1993 to 2022 were reviewed. The results showed that heritability estimates of body measurement traits were medium to high, ranging from...
Chapard L, Gorssen W, Meyermans R, Hooyberghs K, Buys N, Janssens S.Show jumping is a popular equestrian sport that requires a unique combination of jumping capacity and rideability. It has been shown that genetics play an important role in show jumping performance that has significant implications for horse breeding programmes. This gives an important opportunity for studbooks to breed horses with the potential to perform at the highest level in show jumping competitions. However, show jumping competitions are performed at various levels (from recreational to international level) but only national competition results are used by Warmblood studbooks in most ge...
Baville E, Carstanjen B, Thomas-Cancian A, Calgaro A, Bonnet N, Tiret L, Gache V, Abitbol M.Supernumerary digits, or polydactyly, have been described in various species including humans, wild and domestic animals. In horses, it represents the most common congenital limb malformation, which has only been described in isolated cases or nuclear families. Molecular aetiology has not been reported. Objective: To characterise the phenotype of a non-syndromic pre-axial polydactyly in a horse family and to decipher the inheritance pattern. Methods: Retrospective study. Methods: Forty-three members of the family including a previously reported polydactyl case were recruited. Available clinica...
Ziadi C, Demyda-Peyrás S, Valera M, Perdomo-González D, Laseca N, Rodríguez-Sainz de Los Terreros A, Encina A, Azor P, Molina A.The single-step best linear unbiased predictor (ssGBLUP) has emerged as a reference method for genomic selection in recent years due to its advantages over traditional approaches. Although its application in horses remains limited, ssGBLUP has demonstrated the potential to improve the reliability of estimated breeding values in livestock species. This study aimed to assess the impact of incorporating genomic data using single-step restricted maximum likelihood (ssGREML) on reliability (R) in the Pura Raza Española (PRE) horse breed, compared to traditional pedigree-based REML. Methods: The an...
McGivney CL, McGivney BA, Farries G, Gough KF, Han H, Holtby AR, MacHugh DE, Katz LM, Hill EW.Equine recurrent laryngeal neuropathy (RLN) is an economically important upper respiratory tract (URT) disease with a genetic contribution to risk, but genetic variants independent of height have not been identified for Thoroughbreds. The method of clinical assessment for RLN is critical to accurately phenotype groups for genetic studies. Objective: To identify genetic risk loci for RLN in Thoroughbreds in a genome-wide association study (GWAS) following high-resolution phenotyping. Methods: Case-control. Methods: Thoroughbred horses were characterised as RLN cases and controls using resting a...
Makvandi-Nejad S, Hoffman GE, Allen JJ, Chu E, Gu E, Chandler AM, Loredo AI, Bellone RR, Mezey JG, Brooks SA, Sutter NB.Horse body size varies greatly due to intense selection within each breed. American Miniatures are less than one meter tall at the withers while Shires and Percherons can exceed two meters. The genetic basis for this variation is not known. We hypothesize that the breed population structure of the horse should simplify efforts to identify genes controlling size. In support of this, here we show with genome-wide association scans (GWAS) that genetic variation at just four loci can explain the great majority of horse size variation. Unlike humans, which are naturally reproducing and possess many...
Ytrehus B, Carlson CS, Ekman S.Osteochondrosis is a common and clinically important joint disorder that occurs in human beings and in multiple animal species, most commonly pigs, horses, and dogs. This disorder is defined as a focal disturbance of enchondral ossification and is regarded as having a multifactorial etiology, with no single factor accounting for all aspects of the disease. The most commonly cited etiologic factors are heredity, rapid growth, anatomic conformation, trauma, and dietary imbalances; however, only heredity and anatomic conformation are well supported by the scientific literature. The way in which t...
Signer-Hasler H, Flury C, Haase B, Burger D, Simianer H, Leeb T, Rieder S.The molecular analysis of genes influencing human height has been notoriously difficult. Genome-wide association studies (GWAS) for height in humans based on tens of thousands to hundreds of thousands of samples so far revealed ∼200 loci for human height explaining only 20% of the heritability. In domestic animals isolated populations with a greatly reduced genetic heterogeneity facilitate a more efficient analysis of complex traits. We performed a genome-wide association study on 1,077 Franches-Montagnes (FM) horses using ∼40,000 SNPs. Our study revealed two QTL for height at withers on c...
Tetens J, Widmann P, Kühn C, Thaller G.A genome-wide association scan for loci affecting withers height was conducted in 782 German Warmblood stallions, which were genotyped using the Illumina EquineSNP50 Bead Chip. A principal components approach was applied to correct for population structure. The analysis revealed a single major QTL on ECA3 explaining ~18 per cent of the phenotypic variance, which is in concordance with recent reports from other horse populations. The LCORL/NCAPG locus represents a strong candidate gene for this QTL. This locus is among a small number that have consistently been identified to influence human hei...
Hausberger M, Bruderer C, Le Scolan N, Pierre JS.The aim of the present study was to broach the question of the relative influence of different genetic and environmental factors on different temperament/personality traits of horses (Equus caballus). The researchers submitted 702 horses to standardized experimental tests and investigated 9 factors, either genetic or environmental. Genetic factors, such as sire or breed, seemed to influence more neophobic reactions, whereas environmental factors, such as the type of work, seemed to play a more dominant role in reactions to social separation or learning abilities. Additive effects were evident,...
Frischknecht M, Jagannathan V, Plattet P, Neuditschko M, Signer-Hasler H, Bachmann I, Pacholewska A, Drögemüller C, Dietschi E, Flury C, Rieder S....The identification of quantitative trait loci (QTL) such as height and their underlying causative variants is still challenging and often requires large sample sizes. In humans hundreds of loci with small effects control the heritable portion of height variability. In domestic animals, typically only a few loci with comparatively large effects explain a major fraction of the heritability. We investigated height at withers in Shetland ponies and mapped a QTL to ECA 6 by genome-wide association (GWAS) using a small cohort of only 48 animals and the Illumina equine SNP70 BeadChip. Fine-mapping re...
Mitton JB, Schuster WS, Cothran EG, De Fries JC.Specific formulations are derived for the correlation between the heterozygosity of a randomly mating parent and its offspring for a diallelic locus, and for the correlation when multiple loci are considered. The expected correlation is maximal, approaching r = 0.50, when allelic frequencies are highly asymmetric, and it is zero when the allelic frequencies are equal to 0.50. Parent-offspring correlations, up to a maximum of 0.50 for diallelic loci, indicate that levels of heterozygosity can respond to selection. Multilocus allozyme data from limber pine, Pinus flexilis, and from horses of sta...
Seltenhammer MH, Simhofer H, Scherzer S, Zechner R, Curik I, Sölkner J, Brandt SM, Jansen B, Pehamberger H, Eisenmenger E.Equine melanomas occur most commonly in grey horses at age 5 years or more. Generally, benign and malignant melanomas are distinguished by microscopy, but a more distinct classification would be helpful. Objective: The objectives of this study were to gain further evidence concerning the occurrence of melanotic tumours, and to evaluate the impact of heredity on melanoma development. Methods: A clinical study was conducted on a defined population of 296 grey horses of Lipizzaner breed. Individuals were classified according to their stage of disease using a 0-5 scale. Heritability was estimated ...
Jagannathan V, Gerber V, Rieder S, Tetens J, Thaller G, Drögemüller C, Leeb T.Whole-genome sequencing studies are vital to gain a thorough understanding of genomic variation. Here, we summarize the results of a whole-genome sequencing study comprising 88 horses and ponies from diverse breeds at 19.1× average coverage. The paired-end reads were mapped to the current EquCab3.0 horse reference genome assembly, and we identified approximately 23.5 million single nucleotide variants and 2.3 million short indel variants. Our dataset included at least 7 million variants that were not previously reported. On average, each individual horse genome carried ∼5.7 million single n...
Curik I, Druml T, Seltenhammer M, Sundström E, Pielberg GR, Andersson L, Sölkner J.The dominant phenotype of greying with age in horses, caused by a 4.6-kb duplication in intron 6 of STX17, is associated with a high incidence of melanoma and vitiligo-like skin depigmentation. However, the progressive greying and the incidence of melanoma, vitiligo-like depigmentation, and amount of speckling in these horses do not follow a simple inheritance pattern. To understand their inheritance, we analysed the melanoma grade, grey level, vitiligo grade, and speckling grade of 1,119 Grey horses (7,146 measurements) measured in six countries over a 9-year period. We estimated narrow sense...
Wallis N, Raffan E.Obesity is one of the most prevalent health conditions in humans and companion animals globally. It is associated with premature mortality, metabolic dysfunction, and multiple health conditions across species. Obesity is, therefore, of importance in the fields of medicine and veterinary medicine. The regulation of adiposity is a homeostatic process vulnerable to disruption by a multitude of genetic and environmental factors. It is well established that the heritability of obesity is high in humans and laboratory animals, with ample evidence that the same is true in companion animals. In this r...
Gerber V, Baleri D, Klukowska-Rötzler J, Swinburne JE, Dolf G.Mode of inheritance of equine recurrent airway obstruction (RAO) is unknown. Objective: Major genes are responsible for RAO. Methods: Direct offspring of 2 RAO-affected Warmblood stallions (n = 197; n = 163) and a representative sample of Swiss Warmbloods (n = 401). Methods: One environmental and 4 genetic models (general, mixed inheritance, major gene, and polygene) were tested for Horse Owner Assessed Respiratory Signs Index (1-4, unaffected to severely affected) by segregation analyses of the 2 half-sib sire families, both combined and separately, using prevalences estimated in a representa...
Gaffney B, Cunningham EP.Thoroughbred horses have been bred exclusively for racing in England since Tudor times and thoroughbred horse racing is now practised in over 40 countries and involves more than half-a-million horses worldwide. The genetic origins of the thoroughbred go back largely to horses imported from the Middle East and North Africa to England in the late seventeenth and early eighteenth centuries. Since the establishment of the Stud Book in 1791, the population has been effectively closed to outside sources, and over 80% of the thoroughbred population's gene pool derives from 31 known ancestors from thi...
Finno CJ, Famula T, Aleman M, Higgins RJ, Madigan JE, Bannasch DL.Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) is a neurodegenerative disorder affecting young horses of various breeds that resembles ataxia with vitamin E deficiency in humans, an inherited disorder caused by mutations in the alpha-tocopherol transfer protein gene (TTPA). To evaluate variants found upon sequencing TTPA in the horse, the mode of inheritance for NAD/EDM had to be established. Objective: NAD/EDM in the American Quarter Horse (QH) is caused by a mutation in TTPA. Methods: 88 clinically phenotyped (35 affected [ataxia score ≥2], 53 unaffected) QH...
Jeffcott LB.This paper reviews current developments in equine osteochondrosis complex and the clinical syndromes associated with it. Although the primary lesion has been defined as a failure of endochondral ossification, its definitive cause is unknown and appears to involve heredity, growth rate, nutrition, mineral imbalance, endocrinological dysfunction and biomechanical trauma. Despite the international importance of osteochondrosis in horses, surprisingly few controlled investigations have been performed on its pathogenesis. The studies that have been conducted suggest that local effects on differenti...
Ekman S, Carlson CS.Osteochondrosis is a disorder of epiphyseal cartilage about which there is considerable confusion in the literature. We believe that this is due to the fact that osteochondrosis has been studied in the chronic stage when the lesions are morphologically complicated and the initial causative insult is impossible to determine. The etiology of osteochondrosis appears to be multifactorial, with trauma, hereditary factors and rapid growth, nutritional factors, and ischemia all having a role in its pathogenesis. Although predilection sites are variable among species, the morphology of the early lesio...
Mayhew IG, Brown CM, Stowe HD, Trapp AL, Derksen FJ, Clement SF.Two horse farms, on which there was a high incidence of proven and suspected equine degenerative myeloencephalopathy (EDM), were studied. Symmetric ataxia and paresis, along with laryngeal adductor, cervicofacial, local cervical, and cutaneous trunci hyporeflexia, characterized the syndrome. Serum vitamin E concentration reflected a deficient state in affected and unaffected horses on both farms when compared with selected reference groups and with published values. A high incidence of the disease was evident in offspring of two particular sires on one farm. Vitamin E supplementation resulted ...
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...
Ducro BJ, Bovenhuis H, Back W.Warmblood horse studbooks aim to breed horses with a conformation that will enable elite future performance, but reduce the risk of injuries and lameness. Negative conformational traits, such as asymmetrical or 'uneven' forefeet would possibly diminish performance. Objective: To assess the prevalence and heritability of uneven feet and its genetic relationship to other conformation traits as well as to sporting performance later in life in Warmblood riding horses. Methods: The databases of the Royal Dutch Warmblood Studbook (KWPN, n = 44,840 horses) and Royal Dutch Equestrian Sports Federation...
Norton EM, Avila F, Schultz NE, Mickelson JR, Geor RJ, McCue ME.Ponies are highly susceptible to metabolic derangements including hyperinsulinemia, insulin resistance, and adiposity. Objective: Genetic loci affecting height in ponies have pleiotropic effects on metabolic pathways and increase the susceptibility to equine metabolic syndrome (EMS). Methods: Two hundred ninety-four Welsh ponies and 529 horses. Methods: Retrospective study of horses phenotyped for metabolic traits. Correlations between height and metabolic traits were assessed by Pearson's correlation coefficients. Complementary genome-wide analysis methods were used to identify a region of in...
Rustin M, Janssens S, Buys N, Gengler N.Genetic parameters for the height at withers, 27 linear type and six linear gait traits were estimated for the Belgian warmblood horse. Observations on 987 mares, mostly 3 years old, were analysed using a multi-trait animal model. The statistical model included appraiser, age and location (date x place of appraisal) as fixed effects. Genetic parameters were estimated using a canonical transformation and an expectation-maximization restricted maximum likelihood algorithm with an additional deceleration step. Estimates of heritability for the 33 linear traits were between 0.15 and 0.55. Heritabi...
Norton EM, Schultz NE, Rendahl AK, Mcfarlane D, Geor RJ, Mickelson JR, McCue ME.Equine metabolic syndrome (EMS) is a complex clinical disorder with both environmental and genetic factors contributing to EMS phenotypes. Estimates of heritability determine the proportion of variation in a trait that is attributable to genetics. Objective: To provide heritability estimates for nine metabolic traits associated with EMS in two high-risk breeds. Methods: Retrospective cohort study. Methods: High-density single-nucleotide polymorphism (SNP) genotype data was used to estimate the heritability (h ) of nine metabolic traits relevant to EMS in a cohort of 264 Welsh ponies and 286 M...
Grøndahl AM, Dolvik NI.Radiography of the tibiotarsal and metacarpo- and metatarsophalangeal joints was performed on 753 Standardbred trotters (6 to 21 months old) born in 1988. The surveyed population was drawn at random from all parts of Norway and represented about 60% of Standardbred trotters born the same year. Osteochondrosis in the tibiotarsal joint was diagnosed in 108 (14.3%) horses, and the prevalence of disease in progeny groups > 10 ranged from 0 to 69%. Bony fragments in the palmar/plantar portion of the metacarpo- and metatarsophalangeal joints were diagnosed in 89 (11.8%) horses, and the prevalence of...
Polak G, Gurgul A, Jasielczuk I, Szmatoła T, Krupiński J, Bugno-Poniewierska M.Traditionally, pedigree-based relationship coefficients were used to manage inbreeding and control inbreeding depression that occurs within populations. The extensive incorporation of genomic data in livestock breeding creates the opportunity to develop and implement methods to manage populations at the genomic level. Consequently, the realized proportion of the genome that two individuals share can be more accurately estimated instead of using pedigree information to estimate the expected proportion of shared alleles. To make use of this improvement, in this study we evaluated the genomic inb...
Graves KT, Henney PJ, Ennis RB.Laminin 5 is a heterotrimeric basement membrane protein integral to the structure and function of the dermal-epidermal junction. It consists of three glycoprotein subunits: the alpha3, beta3 and gamma2 chains, which are encoded by the LAMA3, LAMB3 and LAMC2 genes respectively. A mutation in any of these genes results in the condition known as hereditary junctional epidermolysis bullosa (JEB). A 6589-bp deletion spanning exons 24-27 was found in the LAMA3 gene in American Saddlebred foals born with the skin-blistering condition epitheliogenesis imperfecta. The deletion confirms that this autoso...
Naccache F, Metzger J, Distl O.Osteochondrosis (OC) is an injury to cartilage canals with a following necrosis in the growth cartilage, from there it can develop to osteochondrosis dissecans (OCD). Due to its high impact in the equine industry, new insights into predisposing factors and potential high-risk genetic variants are warranted. This article reviews advancements in quantitative and molecular genetics in refining estimation of genetic parameters and identifying predisposing genetic loci. Heritabilities were highest for hock OC with estimates at 0.29-0.46 in Hanoverian warmblood and Norwegian trotters, whereas in Tho...
Dupuis MC, Zhang Z, Druet T, Denoix JM, Charlier C, Lekeux P, Georges M.Recurrent laryngeal neuropathy (RLN) is a major upper-airway disease of horses that causes abnormal respiratory noise during exercise and can impair performance. Etiopathogenesis remains unclear but genetic factors have been suspected for many decades. The objective of this study was to identify risk loci associated with RLN. To that end we genotyped 234 cases (196 Warmbloods, 20 Trotters, 14 Thoroughbreds, and 4 Draft horses), 228 breed-matched controls, and 69 parents with the Illumina Equine SNP50 BeadChip. Using these data, we quantified population structure and performed single-marker and...
Ablondi M, Vasini M, Beretti V, Superchi P, Sabbioni A.Genetic diversity is a key factor for both adaptation and response to selection. The loss of genetic diversity causes a decrease in individual fitness, and it has a dramatically negative effect on population lifespan in the long term. This study aimed at exploring the genetic diversity at pedigree level of the Bardigiano horse breed, which is a native breed from Italy shaped for living in rural areas. In 1977, the Bardigiano studbook was founded to preserve the breed and for improving its use for riding and draft purposes. Pedigree data contained 9,469 horses, of which 3,416 were alive. Demog...
