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.
Cervantes I, Gutiérrez JP, García-Ballesteros S, Varona L.The racing time and rank at finish traits are commonly used for endurance horse breeding programs as a measure of their performance. Even so, given the nature of endurance competitions, many horses do not finish the race. However, the exclusion of non placed horses from the dataset could have an influence on the prediction of individual breeding values. The objective of the present paper was to develop a multitrait model including race time (T), rank (R) and placing (P), with different methodologies, to improve the genetic evaluation in endurance competitions in Spain. The database contained 6...
Norton E, McCue ME.A role for a genetic contribution to equine metabolic syndrome (EMS) and pars pituitary intermedia dysfunction (PPID) has been hypothesized. Heritability estimates of EMS biochemical measurements were consistent with moderately to highly heritable traits. Further, genome-wide association analyses have identified hundreds of regions of the genome contributing to EMS and candidate variants have been identified. The genetics of PPID has not yet been proven. Continued research for the specific genetic risk factors for both EMS and PPID is crucial for gaining a better understanding of the pathophys...
Fousse SL, Stern JA.There have been some advances in understanding the genetic contribution to ventricular septal defects in Arabians, sudden death in racehorses, and atrial fibrillation in racehorses. No genetic analyses have been published for aortic rupture in Friesians or atrioventricular block in donkeys despite strong evidence for a genetic cause. To date, no genetic mutation has been identified for any equid cardiac disease. With the advancement of genetic tools and resources, we are moving closer to discoveries that may explain the heritable basis of inherited equid cardiac disease.
Linford N, MacKechnie-Guire R, Cassar M.The aim of this trial project was to identify whether buried archaeological remains may have an influence on equine locomotion, through comparison with a non-invasive Ground Penetrating Radar (GPR) survey. This study was conducted at the world-renowned Burghley Horse Trials site, near Stamford, City of Peterborough, U.K. that has a diverse range of heritage assets throughout the wider park land centred on the Grade 1 listed Elizabethan Burghley House. The initial aim of the research was to first use geophysical survey to identify and characterise archaeological remains, and then to determine a...
Ricard A, Dumont Saint Priest B, Danvy S, Barrey E.The aim of this study was to evaluate the genetic component of the locomotor jumping ability, via a wearable accelerometer sensor, and to estimate the genetic correlation with performance in competition, to introduce such criteria in selection schema. A sample of 1,056 young 3-year-old horses were equipped with a 3-dimensional accelerometer during a free jumping test, in regular breeding shows from 2015 to 2017. Seven variables were extracted from the dorso-ventral acceleration curve for the last three jumps over a double bar obstacle of 1.15 m for the front pole and 1.20 m for the back pole w...
Giontella A, Sarti FM, Biggio GP, Giovannini S, Cherchi R, Pieramati C, Silvestrelli M.The purpose of this study was to estimate the heritability and genetic correlations of four biometric measurements and an overall score (OS) in the Sardinian Anglo-Arab horse (SAA); moreover, the effect of inbreeding on these traits was investigated. A dataset with 43,624 horses (27,052 females and 16,572 males) was provided by the Agricultural Research Agency of Sardinia (AGRIS). Cannon bone circumference (BC), chest girth (CG), shoulder length (SL), and withers height (WH) were measured on 6033 SAA horses born in Sardinia between 1967 and 2005; beside the measurements, an overall score (OS) ...
Cervantes I, Bodin L, Valera M, Molina A, Gutiérrez JP.Control of the environmental variability by genetic selection offers possibilities for new selection objectives for productive traits. This methodology aims at reducing heterogeneity in productive traits and has been applied to several traits and species for which animal homogeneity is profitable. In horse breeding programmes, rank in competitions is a common selection objective but has been challenging to model. In this study, the parameters of environmental variability for the rank of a horse were computed to analyse the capability of a horse to maintain the best ranking across competitions ...
Todd ET, Hamilton NA, Velie BD, Thomson PC.Horses produce only one foal from an eleven-month gestation period, making the maintenance of high reproductive rates essential. Genetic bottlenecks and inbreeding can increase the frequency of deleterious variants, resulting in reduced reproductive levels in a population. In this study we examined the influence of inbreeding levels on foaling rate, gestation length and secondary sex ratio in Australian Thoroughbred mares. We also investigated the genetic change in these traits throughout the history of the breed. Phenotypic data were obtained from 27,262 breeding records of Thoroughbred mares...
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...
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 ...
Walker NL, Patout AR, Cater M.Hereditary equine regional derma asthenia (HERDA), an autosomal-recessive trait, found in Quarter Horses, causes abnormal collagen structure. Owing to current breeding practices, 3.5% of registered quarter horses and 28.3% of the cow horse population are heterozygote carriers. Research demonstrated homozygote horses develop hyperextensible skin susceptible to injury and other abnormal tissues containing high fibrillar collagen content. No research exists determining the effects of the disease in heterozygote carriers. Currently, 30% of cutting sires are HERDA carriers, potentially increasing t...
Medeiros BR, Garbade P, Seixas L, Peripolli V, McManus C.The aim of this study was to evaluate genetic parameters for subjective scores given at the Brazilian Sport Horse (BSH) Stallion Approval by estimating heritability (h) for morphological, gait, and jumping traits and genetic correlations (γ) among the functional ones and by verifying selection feasibility. The analysis included 1179 complete evaluations from 294 horses, by 4.26 ± 0.96 judges. Each trait was evaluated using mixed models in SAS® v9.2, considering the individual as a random effect. Variance components and genetic parameters were obtained by single and two-trait animal mode...
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 ...
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...
Greiser T, Sieme H, Martinsson G, Distl O.Objectives of the present study were to estimate genetic parameters for frozen-thawed semen traits of 271 fertile German Warmblood stallions and genetic correlations with raw semen quality traits. Semen samples were collected from stallions utilized for semen collection and artificial insemination (AI) on the Lower Saxon National Stud Celle and the North Rhine-Westphalian National Stud Warendorf. Semen quality variables were analyzed in 63,972 raw (gel-free volume, concentration, progressive motility, number of sperm) and 3681 frozen-thawed samples (motility, DNA fragmentation index (DFI), non...
Petersen JL, Lewis RM, Embertson R, Valberg SJ, Holcombe SJ.Large colon volvulus (LCV) is a life-threatening form of colic that occurs when the large colon rotates 360° or more on its axis, resulting in colonic distention and ischaemia. Any horse can suffer from LCV, but the risk is greatest for periparturient Thoroughbred broodmares; the objective of this study was to estimate the heritability of LCV in these horses. The criteria for classification as an LCV case were being a Thoroughbred broodmare from one of three farms in central Kentucky and having had surgical correction for LCV. Controls were identified as Thoroughbred broodmares present on the...
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...
Ablondi M, Summer A, Vasini M, Simoni M, Sabbioni A.Horses are nowadays mainly used for sport and leisure purposes, and several local breeds, traditionally used in agriculture, are exposed to the risk of extinction. The long-term survival of local horse breeds depends on strategies to both monitor their genetic diversity and to find their sustainable role in the equine market. Thus, several local horse breeds need to adapt their breeding objective to allow a modernization process. The Bardigiano is an example of such horse breeds; we, therefore, studied the existing evaluation protocol from a genetic standpoint to assess the protocol's suitabil...
McElroy A, Rashmir A, Manfredi J, Sledge D, Carr E, Stopa E, Klinge P.Myodural bridges have been described in various species as connective tissue structures "bridging" small cranio-cervical muscles to the dura. Myodural bridges are thought to stabilize the dural sac during head and neck movements and promote cerebrospinal fluid motion; however, their role in neurological diseases has not yet been established. We report ultrasonographic visualization, necropsy, histopathologic and ultrastructural findings of myodural bridges in horses with hereditary equine regional dermal asthenia (HERDA), an equine model of Ehlers-Danlos syndromes. Five HERDA and 5 control hor...
McGivney BA, Hernandez B, Katz LM, MacHugh DE, McGovern SP, Parnell AC, Wiencko HL, Hill EW.Durability traits in Thoroughbred horses are heritable, economically valuable and may affect horse welfare. The aims of this study were to test the hypotheses that (i) durability traits are heritable and (ii) genetic data may be used to predict a horse's potential to have a racecourse start. Heritability for the phenotype 'number of 2- and 3-year-old starts' was estimated to be = 0.11 ± 0.02 (n = 4499). A genome-wide association study identified SNP contributions to the trait. The neurotrimin (NTM), opioid-binding protein/cell adhesion molecule like (OPCML) and prolylcarboxypeptidase ...
Yokomori T, Tozaki T, Mita H, Miyake T, Kakoi H, Kobayashi Y, Kusano K, Itou T.According to oral traditions of horse caretakers and trainers, the differences in the position and number of facial hair whorls may be associated with temperamental traits. Elucidating genetic background of facial hair whorls and its relationship to temperamental traits may promote more efficient breeding and maintenance of racehorses. In this study, we estimated heritabilities of the position and number of facial hair whorls in Japanese Thoroughbred horses. Results: The number of facial hair whorls varied from one to four and heritability estimate in 4024 Thoroughbred horses was low (h2= 0....
Velie BD, Solé M, Fegraeus KJ, Rosengren MK, Røed KH, Ihler CF, Strand E, Lindgren G.Since the 1950s, the Norwegian-Swedish Coldblooded trotter (NSCT) has been intensively selected for harness racing performance. As a result, the racing performance of the NSCT has improved remarkably; however, this improved racing performance has also been accompanied by a gradual increase in inbreeding level. Inbreeding in NSCT has historically been monitored by using traditional methods that are based on pedigree analysis, but with recent advancements in genomics, the NSCT industry has shown interest in adopting molecular approaches for the selection and maintenance of this breed. Consequent...
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 ...
Tozaki T, Miyake T, Kikuchi M, Kakoi H, Hirota KI, Kusano K, Ishikawa Y, Nomura M, Kushiro A, Nagata SI.Thoroughbred racehorses are produced by mating small numbers of Arabian stallions and native British mares, and have been improved by selection of horseracing performance for about 300 years. While these improvements led to good performance as racehorses, they exposed horses to numerous medical disorders, aggravated by extensive exercise. Fractures are frequent medical disorders in Thoroughbred racehorses. In this study, fracture heritability was estimated using 3,927 Japanese Thoroughbred racehorses to elucidate the risk of racehorse fractures. The heritability estimates of all examined frac...
Sánchez-Guerrero MJ, Solé M, Azor PJ, Sölkner J, Valera M.Vitiligo and melanoma are relatively common disorders in grey Pura Raza Español horses and other horse breeds with grey-coloured coats. Objective: To determine the breed prevalence, environmental risks factors and estimate the genetic parameters for vitiligo and melanoma in Pura Raza Español horses. Methods: Retrospective cohort study. Methods: We analysed data from a large worldwide population of Pura Raza Español horses. The database included the vitiligo and melanoma scores, on either a four- or six-point linear scale, of 11,436 horses. Genetic parameters were estimated using a Bayesian ...
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...
Hill EW, McGivney BA, Rooney MF, Katz LM, Parnell A, MacHugh DE.Race distance aptitude in Thoroughbred horses is highly heritable and is influenced largely by variation at the myostatin gene (MSTN). Objective: In addition to MSTN, we hypothesised that other modifying loci contribute to best race distance. Methods: Using 3006 Thoroughbreds, including 835 'elite' horses, which were >3 years old, had race records and were sampled from Europe/Middle-East, Australia/New Zealand, North America and South Africa, we performed genome-wide association (GWA) tests and separately developed a genomic prediction algorithm to comprehensively catalogue additive geneti...
Ghezelsoflou H, Hamidi P, Gharahveysi S.The Iranian Turkoman horse is considered one of the major categories of Iranian native horses. The aim of this research was to study the genetic and nongenetic factors affecting body conformation traits in Iranian Turkoman horses. For this, measurements were performed on body conformation traits of 121 horses. To study the effect of nongenetic factors, the Lsmeans procedure was used. Variance components and heritability were estimated by restricted maximum likelihood method (REML) and AI-REML convergence algorithm. The standard deviation was estimated to be 7.04 cm for croup depth and 2.08 cm ...
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...
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 &...
Oki H, Kusunose R, Nakaoka H, Nishiura A, Miyake T, Sasaki Y.Genetic variation of the behaviour of racehorses is one of the major concerns for racehorse breeders. In this study, the heritabilities of behavioural responses to the inspections of conjunctiva, auscultation and blood sampling and the genetic correlations among them were estimated in the Thoroughbred racehorse. The estimation was done with Bayesian analysis with Gibbs sampling based on the univariate or bivariate threshold animal models. The behavioural responses were scored with four categories at the first entrance quarantine in Miho Training Center of Japan Racing Association from 1993 to ...
Schurink A, Ducro BJ, Heuven HC, van Arendonk JA.Insect bite hypersensitivity (IBH) is a seasonal allergic skin disease in horses caused by bites of certain Culicoides spp. The aim of our study was to investigate the maternal effect on IBH and to estimate the heritability and repeatability of IBH in the Dutch Friesian horse population. Data consisted of 3,453 Dutch Friesian broodmares with 3,763 visual observations on IBH clinical symptoms scored by 12 inspectors during organized foal inspections in 2004 and 2008. Nine percent of the mares (n = 310) were scored in both years. Mares descended from 144 sires and 2,554 dams and 26.2% of the dam...
Velie BD, Raadsma HW, Wade CM, Knight PK, Hamilton NA.Post exercise epistaxis, the manifestation of a severe form of exercise-induced pulmonary haemorrhage (EIPH), has been observed in many equine racing populations. Although multiple analyses have suggested that non-genetic factors may lead to the development of this condition, relatively little consensus has been reached regarding its genetic aetiology. The objective of this study was to provide insight into both genetic and non-genetic factors that may contribute to the expression of epistaxis in the Australian Thoroughbred racing population. Racing records and reported epistaxis occurrences w...
Nazari-Ghadikolaei A, Fikse F, Gelinder Viklund Å, Eriksson S.Assessment protocols to describe the various aspects of conformation, gait and jumping traits on a linear scale were introduced at young horse tests for Swedish Warmblood horses in 2013. The traits scored on a linear scale are assumed to be less subjective and more easily compared across populations than the traditional evaluated traits that are scored relative to the breeding goal. However, the resulting number of traits is considerable, and several of the traits are correlated. The aim of this study was to investigate the interrelationship between the different evaluated and linearly scored ...
Desgorces FD, Berthelot G, Charmantier A, Tafflet M, Schaal K, Jarne P, Toussaint JF.Running speed in animals depends on both genetic and environmental conditions. Maximal speeds were here analysed in horses, dogs and humans using data sets on the 10 best performers covering more than a century of races. This includes a variety of distances in humans (200-1500 m). Speed has been progressing fast in the three species, and this has been followed by a plateau. Based on a Gompertz model, the current best performances reach 97.4% of maximal velocity in greyhounds to 100.3 in humans. Further analysis based on a subset of individuals and using an 'animal model' shows that running spe...
Mota MD, Abrahão AR, Oliveira HN.The aim of the present study was to investigate genetic parameters for racing time in Thoroughbred horses racing at distances between 1000 and 1600 m subdivided into 100-m intervals. The data provided by TURFETOTAL Ltda comprised races that occurred in the Gávea and Cidade Jardim race tracks over a period of 11 years (1992-2002) and consisted of 32,145 races and 238,890 time records. The variance components necessary to obtain the heritability and repeatability estimates of the traits studied were estimated with the MTDFREML program, and animal age at race (3 years old or younger, 4, 5 and ol...
Brault LS, Famula TR, Penedo MC.To determine the mode of inheritance for cerebellar abiotrophy (CA), a neurologic disease in Arabians. Methods: 804 Arabians, including 29 horses (15 males and 14 females) with CA. Methods: Most horses (n = 755) belonged to 1 of 4 paternal families. Among the 29 CA-affected horses, all had clinical signs consistent with the disease; the disease was confirmed histologically following euthanasia in 8 horses. From the pedigree information, inbreeding coefficients were calculated for 16 affected horses and compared with coefficients for a subgroup of 16 unaffected horses. Complex segregation analy...
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...
Valera M, Blesa F, Dos Santos R, Molina A.The length of gestation in Andalusian, or Spanish Purebred (SPB) and Arabian (AB) mares reared in Spain was analysed, based on 766 spontaneous full-term deliveries appertaining to 141 mares of SPB breed and 72 mares of AB breed in 31 breeding seasons. The data were obtained from the Yeguada Militar de Jerez de la Frontera stud farm in Cádiz, Spain. The mean length of gestation was of 336.8+/-0.48 days in the SPB mares and 340.3+/-0.63 days in AB mares. To assess the accurate prediction of time of birth the potential effect of a number of factors was investigated. The influences of the breed, ...
Neuhaus S, Bruendler P, Frey CF, Gottstein B, Doherr MG, Gerber V.Equine recurrent airway obstruction (RAO) shares many characteristics with human asthma. In humans, an inverse relationship between susceptibility to asthma and resistance to parasites is suspected. Objective: Members of a high-incidence RAO half-sibling family (F) shed fewer strongylid eggs compared with RAO-unaffected pasture mates (PM) and that RAO-affected horses shed fewer eggs than RAO-unaffected half-siblings. Methods: Seventy-three F and 73 unrelated, age matched PM. Methods: Cases and controls kept under the same management and deworming regime were examined. Each individual was class...
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 ...
Broström H, Fahlbrink E, Dubath ML, Lazary S.The distribution of equine leucocyte antigens (ELA) in Swedish Halfbreds affected by sarcoid tumors was determined and compared with that of control horses of the same breed. ELA-haplotype A3W13 appeared more frequently in affected horses, resulting in a chi 2 value of 4.45 (P = 0.034) for A3 and 9.05 (P = 0.0026) for W13, respectively. The relative risk factor (RR) could be estimated to 2.13 and 3.00 for A3 and W13, respectively. The etiology fraction (EF) was calculated to 28% and 37% for A3 and W13, respectively. Thus, in the population of Swedish Halfbreds approximately 40% (at least) of t...
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...
Hilla D, Distl O.The main objective of this study is to estimate genetic parameters for osteochondrosis (OC) and osteochondrosis dissecans (OCD) in fetlock, hock and stifle joints as well as for palmar or plantar osteochondral fragments (POFs) and dorsodistal osteochondral fragments (DOFs) in fetlock joints. For this purpose, the results of a standardized radiographic examination of 7396 Hanoverian Warmblood horses were used. Heritabilities and genetic correlations were estimated using residual maximum likelihood (REML) under a linear animal model. Heritability estimates for OC at the different joints were at ...
Kornaś S, Sallé G, Skalska M, David I, Ricard A, Cabaret J.Equine internal parasites, mostly cyathostomins, affect both horse welfare and performance. The appearance of anthelmintic-resistant parasites creates a pressing need for optimising drenching schemes. This optimization may be achieved by identifying genetic markers associated with host susceptibility to infection and then to drench carriers of these markers. The aim of our study was to characterise the genetics of horse resistance to strongyle infection by estimating heritability of this trait in an Arabian pure blood population. A population of 789 Arabian pure blood horses from the Michałó...
Velie BD, Solé M, Fegraeus KJ, Rosengren MK, Røed KH, Ihler CF, Strand E, Lindgren G.Since the 1950s, the Norwegian-Swedish Coldblooded trotter (NSCT) has been intensively selected for harness racing performance. As a result, the racing performance of the NSCT has improved remarkably; however, this improved racing performance has also been accompanied by a gradual increase in inbreeding level. Inbreeding in NSCT has historically been monitored by using traditional methods that are based on pedigree analysis, but with recent advancements in genomics, the NSCT industry has shown interest in adopting molecular approaches for the selection and maintenance of this breed. Consequent...
The Journal of heredityMarch 1, 1987
Volume 78, Issue 2 75-80 doi: 10.1093/oxfordjournals.jhered.a110340
Bowling AT, Ryder OA.Ninety-six Przewalski's horses (Equus przewalskii) were blood typed using systems of inherited blood variants known to be highly effective for parentage testing of domestic horses (E. caballus). Sixteen red cell antigenic factors detected using sera prepared by alloimmunization of domestic horses were shown to be inherited in six systems (A, C, D, P, Q, and U) and in the same patterns as domestic horses. Family data confirmed autosomal, codominant inheritance at five loci of serum protein variants (Al, Tf, Xk, Pi, and Es) and three loci of red cell proteins (PGM, PHI, and Hb). One serum protei...
García-Ballesteros S, Varona L, Valera M, Gutiérrez JP, Cervantes I.Ranking trait was used as a selection criterion for competition horses to estimate racing performance. In the literature the most common approaches to estimate breeding values are the linear or threshold statistical models. However, recent studies have shown that a Thurstonian approach was able to fix the race effect (competitive level of the horses that participate in the same race), thus suggesting a better prediction accuracy of breeding values for ranking trait. The aim of this study was to compare the predictability of linear, threshold and Thurstonian approaches for genetic evaluation of...
Rovere G, Ducro BJ, van Arendonk JA, Norberg E, Madsen P.Sport performance in dressage and show jumping are two important traits in the breeding goals of many studbooks. To determine the optimum selection scheme for jumping and dressage, knowledge is needed on the genetic correlation between both disciplines and between traits measured early in life and performance in competition in each discipline. This study aimed to estimate genetic parameters to support decision-making on specialization of breeding horses for dressage and show jumping in Dutch warmblood horses. Genetic correlations between performance of horses in dressage and show jumping were ...
Signer-Hasler H, Neuditschko M, Koch C, Froidevaux S, Flury C, Burger D, Leeb T, Rieder S.Hereditary variations in head morphology and head malformations are known in many species. The most common variation encountered in horses is maxillary prognathism. Prognathism and brachygnathism are syndromes of the upper and lower jaw, respectively. The resulting malocclusion can negatively affect teeth wear, and is considered a non-desirable trait in breeding programs. We performed a case-control analysis for maxillary prognathism in horses using 96 cases and 763 controls. All horses had been previously genotyped with a commercially available 50 k SNP array. We analyzed the data with a mixe...
Stock KF, Hamann H, Distl O.Genetic parameters were estimated for the prevalence of osseous fragments in distal (DIJ) and proximal interphalangeal (PIJ), fetlock (FJ) and hock joints (HJ) of Hanoverian Warmblood horses by using residual maximum likelihood (REML) with linear animal models. The analyses were based on the results of 10 standardized radiographs of all four limbs of 3725 young riding horses selected for sale at auction. Transformation factors onto the underlying liability scale were verified by a simulation study. The heritability estimates of osseous fragments on the liability scale were in the range of h2 =...
Metzger J, Ohnesorge B, Distl O.Equine guttural pouch tympany (GPT) is a hereditary condition affecting foals in their first months of life. Complex segregation analyses in Arabian and German warmblood horses showed the involvement of a major gene as very likely. Genome-wide linkage and association analyses including a high density marker set of single nucleotide polymorphisms (SNPs) were performed to map the genomic region harbouring the potential major gene for GPT. A total of 85 Arabian and 373 German warmblood horses were genotyped on the Illumina equine SNP50 beadchip. Non-parametric multipoint linkage analyses showed g...
Norris JW, Pratt SM, Auh JH, Wilson SJ, Clutter D, Magdesian KG, Ferraro GL, Tablin F.Bleeding in racing horses associated with exercise appears to be multifactorial, and clinical investigation into severe cases rarely occurs. Previously, we reported a severe bleeding diathesis in a Thoroughbred mare. Herein, we describe the cellular physiology of this defect, provide a diagnostic tool for identifying it, and demonstrate that the dysfunction is heritable. Objective: The subject has a heritable defect in platelet secretion that reduces thrombin generation in the absence of additional plasma factors and delays the onset of thrombin production even in the presence of these factors...
Gene mutations influencing melanocytes also impact on physiological and behavioural functions. In this study, we investigated their association with four different coat colours in the Pura Raza Español (PRE) horse using morphological traits and molecular datasets. Four different subpopulations were identified according to individual coat colour: grey, bay, chestnut and black. Coat colour significantly associated with morphological measurements. Observed and expected heterozygosity values were low in grey compared with the other three subpopulations, suggesting the presence of unique ancestral...
Love S, Wyse CA, Stirk AJ, Stear MJ, Calver P, Voute LC, Mellor DJ.The assessment of belief that equine conformation is associated with performance and durability is a fundamental concept of horsemanship. Surprisingly, there is almost no quantitative evidence to support these beliefs. Objective: To assess the prevalence and heritability of conformational traits in Thoroughbred yearlings, and investigate their significance for subsequent turf flat-racing performance and durability. Methods: Nine selected conformational traits were assessed in a consistent, qualitative manner by a single veterinary observer and entered into a database together with details of p...
Posta J, Somogyvári E, Mihók S.Gene conservation and management of small populations requires proper knowledge of the background and history of the breed. The aim of the study was the evaluation of population structure and changes of the Hungarian Hucul horse population. Population changes were described for the actual breeding stock as well as for groups of 10-year epochs reflecting major periods of change in the breed. Pedigree data of the registered population were analyzed using Endog and GRain software. The average value of equivalent complete generations was above nine for the actual breeding population. The longest g...
Halper J.Though soft tissue disorders have been recognized and described to some detail in several types of domestic animals and small mammals for some years, not much progress has been made in our understanding of the biochemical basis and pathogenesis of these diseases in animals. Ehlers-Danlos syndrome described in dogs already in 1943 and later in cats affects mainly skin in these animals. The involved skin is thin and hyperextensible with easily inflicted injuries resulting in hemorrhagic wounds and atrophic scars. Joint laxity and dislocation common in people are less frequently found in dogs. No...
Halper J.Though soft tissue disorders have been recognized and described to some detail in several types of domestic animals and small mammals for some years, not much progress has been made in our understanding of the biochemical basis and pathogenesis of these diseases in animals. Ehlers-Danlos syndrome described in dogs already in 1943 and later in cats affects mainly skin in these animals. The involved skin is thin and hyperextensible with easily inflicted injuries resulting in hemorrhagic wounds and atrophic scars. Joint laxity and dislocation common in people are less frequently found in dogs. No...
Tozaki T, Miyake T, Kakoi H, Gawahara H, Hirota K, Nakano Y, Kurosawa M.This study evaluated the differences between linear and non-linear modelled heritability estimates of racing performance based on lifetime earnings (LE) and lifetime ranking (LR) in Japanese Thoroughbred racehorses. The heritability estimate (h(2) = 0.25) obtained from a non-linear model based on formal Japan Racing Association ranking was much higher than that obtained from a linear model based on the original trait phenotype (h(2) = 0.11). The linear models showed slightly higher heritability estimates under the trait categorizations than under the original phenotypes, while the non-linear c...
