Equine Breeds Research Articles

Characterisation of white facial markings in Pura Raza Española horses (a worldwide population genetic study)

White markings are characteristic of many equine breeds, being quite common in the Pura Raza Español horses (PRE). These white markings are the result of a lack of melanocytes in the skin and hair. In certain horse breeds, such as the PRE, the presence and extension of white facial markings is penalised in the breed’s patron and morphological competitions, so it would be interesting to include it in their selection genetics programs to select against the presence of this special feature. The aim of this study was to calculate the prevalence of white facial markings in a representative population sample of PRE and determine its prevalence depending on the coat colour, its genetic parameters and the influence of systematic effects. The white facial markings have been classified into 5 score. A total of 42,080 PRE horses were analysed. Genetic parameters were estimated using a Bayesian procedure with the BLUPF90 software. Systematic effects included in the model were: birth period, sex, birth stud geographical area and inbreeding coefficient. The pedigree information included 93,322 horses. The prevalence was 34.2%. Systematics factors were significant in the presentation of facial white markings. Heritability in real scale ranged from 0.53 for black to 0.32 for the chestnut coat colour population, both in the linear heterogeneity model. White facial markings were more prevalent in inbred chestnut males of Spain. The additive genetic base shows that the prevalence could be managed by genetic selection.

Prevalence and factors associated with Leishmania spp. and Toxoplasma gondii infections in apparently healthy horses in Eastern Spain

Leishmaniasis and toxoplasmosis are two of the most common parasitic zoonoses. Leishmaniasis is endemic to 98 countries around the world, whereas toxoplasmosis is widely distributed throughout the world, causing significant health expenditure. Horses can play a relevant role in the transmission of the disease, being a silent reservoir, as clinical signs are not common. Serum samples from 166 horses living in eastern Spain (Mediterranean basin) were analysed to determine the presence of antibodies against Leishmania spp. and T. gondii by ELISA (Enzyme-linked Immunosorbent Assay.) The risk factors evaluated were the geographical area and the relative humidity and average temperature, and epidemiological factors such as sex, reproductive status, age, breed, morphotype, living with other domestic animals, use and access to the outdoors. Seroprevalence of Leishmania spp. and T. gondii infection was found 28.92%, and 16.27% respectively, whereas co-infection of the two parasites was found only in two males. Leishmania seroprevalence was high in castrated males and several mesodolichomorphic equine breeds used for teaching, as well as in outdoor animals. The most elevated seroprevalence was found in winter with higher levels of rainfall, whereas high seroprevalence of T. gondii was found in crossbreeding animals and those used for breeding. High seroprevalence of Leishmania spp. and T. gondii was found in horses of the Mediterranean basin. These data suggest that horses can act as a silent reservoir and that this species has high potential for transmission to humans, outdoor animals and in geographical areas with high average rainfall.

Hematological and biochemical reference values for the Brazilian Pony breed

The aim of this study was to characterize the hematological profile of the equine Brazilian Pony breed herds in northern of Rio de Janeiro state, Brazil. Blood samples were separated in categories: adult stallions, pregnant mares and non-pregnant mares. The red blood cells (RBC), packed cell volume (PCV), hemoglobin (Hgb), main corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), white blood cells (WBC) and differential count of basophils (Baso), eosinophils (Eos), band cells (Bands), segmented neutrophils (Neut), lymphocytes (Lym), monocytes (Mono), and platelets (Plat) were evaluated. The biochemical parameters of urea (Urea), alanine aminotransferase (ALP), aspartate aminotransferase (AST), gamma glutamyl transpeptidase (GGT), and creatinine (Creatinine) were measured in pregnant and non-pregnant mares. Analysis of variance was carried out with difference of hematological parameters between males and females. Also, analysis of variance was used to verify the effect of pregnancy on biochemical parameters. There was effect of sex on RBC, hemoglobin, VCM and MHCH, but PVC and MHC were not affected by sex. Higher means were observed in females. There was an effect of sex on WBC, eosinophils and neutrophils. There was effect of pregnancy on AST, but no effect on urea, GGT and Creatinine. According to the results obtained in this study, it can be concluded that the analysis of the blood count and the biochemical of the Brazilian Pony reveals specificities compared to other equine breeds. Thus, these results could be used as biomarkers for the evaluation of the Brazilian Pony breed in Rio de Janeiro.

Microbiome analysis reveals the differences in gut fungal community between Dutch Warmblood and Mongolian horses

Similar to gut bacterial community, gut fungal community are also an important part of the gut microbiota and play crucial roles in host immune regulation and metabolism. However, most studies have focused on the gut bacterial community, and research on the gut fungal community has been limited. Dutch Warmblood (DWH) and Mongolian horses (MGH) are important equine breeds, but little research has been done on their gut fungal community. Here, we assessed differences in gut fungal community between two horse species. Results showed that a total of 2159 OTUs were found in the Dutch Warmblood and Mongolian horses, of which 308 were common. Between-group analyzes of microbial diversity showed no differences in the alpha and beta diversity of gut fungal community between the two horse species. Microbiological taxonomic surveys showed that the dominant fungal phyla (Neocallimastigomycota and Ascomycota) and genera (unclassified_Neocallimastigaceae and Anaeromyces) were the same without being affected by species. Although the types of dominant fungal phyla did not change, the abundances of some fungal genera changed significantly. Results of Metastats analysis showed that there were a total of 206 fungal genera that were significantly different between the two horses, among which 78 genera showed an increase and 127 genera significantly decreased in Dutch Warmblood horses compared with Mongolian horses. In conclusion, this study investigated the composition and structure of the gut fungal community of Dutch Warmblood and Mongolian horses and found significant differences in gut fungal community between both breeds. Notably, this is the first exploration of the differences in the gut fungal community of both breeds, which may help to understand the distribution characteristics of the gut fungal community of different breeds of horses and reveal the differences in the traits of different horses.

Phenotypic characterisation and production system of the Nordestino horse from a multivariate perspective

Zootechnical data is a big challenge in the extensive rearing system of Brazilian locally adapted breeds once smallholdings with limited resources and funds rear them. So, information on Brazil's breeding system of locally adapted breeds is still scarce; this situation is more challenging for equine breeds. The present study aimed to describe the local rearing systems and the phenotypic profile of the Nordestino horse breed in Paraíba state and contribute to breed conservation. Data from males (entire and castrated) and females from 50 municipalities in Paraíba state were used. Two hundred sixty-nine animals (111 females, 121 castrated males, and 37 entire males) from 129 breeders were analyzed. A questionnaire consisting of direct and objective questions was applied to understand the breeding system adopted. There was a predominance of the extensive breeding system (85%), which reflects the adaptation of the Nordestino Horse to the region's natural conditions. The lower frequency of use of cultivated pastures may be related to issues of economic viability since the maintenance of cultivated pastures may require additional investments compared to the use of natural pastures. Entire males had a minimum withers height (WH) of 135 cm. Of the 11 morphometric measurements, only five were considered discriminating by the stepwise analysis. The remaining Nordestino horses have morphological characteristics within the breed standard.

Baselining physiological parameters in three muscles across three equine breeds. What can we learn from the horse?

Mapping-out baseline physiological muscle parameters with their metabolic blueprint across multiple archetype equine breeds, will contribute to better understanding their functionality, even across species. Aims: 1) to map out and compare the baseline fiber type composition, fiber type and mean fiber cross-sectional area (fCSA, mfCSA) and metabolic blueprint of three muscles in 3 different breeds 2) to study possible associations between differences in histomorphological parameters and baseline metabolism. Methods: Muscle biopsies [m. pectoralis (PM), m. vastus lateralis (VL) and m. semitendinosus (ST)] were harvested of 7 untrained Friesians, 12 Standardbred and 4 Warmblood mares. Untargeted metabolomics was performed on the VL and PM of Friesian and Warmblood horses and the VL of Standardbreds using UHPLC/MS/MS and GC/MS. Breed effect on fiber type percentage and fCSA and mfCSA was tested with Kruskal-Wallis. Breeds were compared with Wilcoxon rank-sum test, with Bonferroni correction. Spearman correlation explored the association between the metabolic blueprint and morphometric parameters. Results: The ST was least and the VL most discriminative across breeds. In Standardbreds, a significantly higher proportion of type IIA fibers was represented in PM and VL. Friesians showed a significantly higher representation of type IIX fibers in the PM. No significant differences in fCSA were present across breeds. A significantly larger mfCSA was seen in the VL of Standardbreds. Lipid and nucleotide super pathways were significantly more upregulated in Friesians, with increased activity of short and medium-chain acylcarnitines together with increased abundance of long chain and polyunsaturated fatty acids. Standardbreds showed highly active xenobiotic pathways and high activity of long and very long chain acylcarnitines. Amino acid metabolism was similar across breeds, with branched and aromatic amino acid sub-pathways being highly active in Friesians. Carbohydrate, amino acid and nucleotide super pathways and carnitine metabolism showed higher activity in Warmbloods compared to Standardbreds. Conclusion: Results show important metabolic differences between equine breeds for lipid, amino acid, nucleotide and carbohydrate metabolism and in that order. Mapping the metabolic profile together with morphometric parameters provides trainers, owners and researchers with crucial information to develop future strategies with respect to customized training and dietary regimens to reach full potential in optimal welfare.

The Genetic Diversity of Horse Native Breeds in Russia.

Horses were domesticated later than other farm animals. Horse breeds have been selectively developed by humans to satisfy different needs and purposes. The factory and indigenous breeds are of particular interest, having been bred in purity for many centuries without the addition of foreign blood. Data from 31 stud farms, as well as ranches, located in fifteen regions of the Russian Federation were used in this work. DNA was sampled from 102 stallions of 11 breeds: Arabian, Akhal-Teke, Don, Orlov Trotter, Vladimir Heavy Draft, Russian Heavy Draft, Soviet Heavy Draft, Kabardin, Yakut, Tuva, and Vyatka. Data on the origin of each animal from which the material was collected were taken into account. DNA genotyping was carried out using GGP Equine 70 k ® array chips (Thermo Fisher Scientific, USA). Genetic diversity of horse breeds was estimated using Admixture 1.3. and PLINK 1.9 software. FROH inbreeding was computed via the R detectRUNS package. The minimum length for ROH was set at 1 Mb to reduce the occurrence of false positives. We conducted PCA analysis using PLINK 1.9, and used the ggplot2 library in R for visualizing the results. Indigenous equine breeds, such as Vyatka, Tuva, and Yakut, are very hardy, and well adapted to local environmental and climatic conditions. They are employed as draft power, as well as for milk and meat. Both the Akhal-Teke breed and the Arabian breed have retained a minimum effective population size over many generations. We note significant accumulations of homozygosity in these breeds. In equestrian sports, performance is a top priority. ADMIXTURE and PCA analyses showed similarities between Don equine breeds and Kabardin, as well as some Arabian breed animals. Earlier research indicated the presence of thoroughbred traits in Don stallions. The Orlov Trotter breed stands out as a separate cluster in the structural and PCA analyses. Considering the small population size of this breed, our study found high FROH in all tested animals. The general reduction in the diversity of the horse breed gene pool, due to numerous crosses for breed improvement with thoroughbreds, has lead to a decline in the differences between the top sporting breeds. Our study presents new opportunities for exploring the genetic factors that influence the formation of adaptive traits in indigenous breeds, and for finding ways to preserve genetic diversity for effective population reproduction.

PSVII-16 A Method to Analyze the Vertical Acceleration of the Peruvian Paso Horse for Animal Breeding Purposes

Abstract The Peruvian Paso Horse (CPP in Spanish) is an equine local breed in Peru. In this kind of horse, the smoothness and harmony of its movement come from the combination of the mechanisms of movement during the “paso llano” and the correct degrees of execution of the overreach with the adornments. The Peruvian Paso horse is internationally recognized for the smoothness of its gait, which is known as "the smoothest riding horse in the world". This characteristic is evaluated in breed competitions. However, at this time, there is no measure available to determine the smoothness of the gait objectively, relying solely on the perception of the judge during the evaluation. The objective of this research is to analyze the vertical acceleration of each animal (ai) during the “paso llano” gait in CPP. Sixty-five stallions and sixteen mares were measured through video recordings using a camera with a resolution of 1920 x 1080 megapixels at 30 frames/s. The animals were pulled by an operator at a “Paso llano” with an approximate speed between 2.5 and 4 m/s. The gait of the horse was recorded by filming on a tripod with a fixed position positioned horizontally at 1.3 meters height and 12 meters from the middle of the line of motion. To identify the reference point for measuring, a 4 x 4 cm tape was attached to the left side of the croup. KINOVEA software version 0.9.5 (https://www.kinovea.org/) was used to analyze the vertical acceleration every 33 ms. The digitized coordinates are passed through the Butterworth filter at a cutoff frequency computed by estimating the autocorrelation of residuals and finding the frequency yielding the residuals that are the least autocorrelated. The filtered dataset corresponding to this cutoff frequency is kept as the result. A graphical representation can be seen in Figure 1. Root-mean-square (RMS) for each horse was calculated as follows: RMS = √(∑ a2i / n), (ai with i = 1 . . . n). To determine normality assumptions, the Anderson-Darling test with P > 0.05 was applied. To determine if there is a difference between sexes, an ANOVA with P < 0.05 was applied. Levene's test was applied to determine the equality of variances. The descriptive statistics are presented in Table 1. The Anderson-Darling test obtained P = 0.969, therefore, the assumptions of the normal distribution are fulfilled. Levene's test obtained a P = 0.035, therefore, the assumptions of equal variance between sexes are not met. ANOVA with heterogeneity correction Welch was P = 0.891. The results show that there is no difference in vertical acceleration between males and females. The estimation of RMS allows an objective analysis of the smoothness of gait in the CPP and can be used as a selection criterion in selection for breeding plans.

Prevalence and Factors Related to Leishmania infantum Infection in Healthy Horses (Equus caballus) from Eastern Spain.

Leishmaniosis is a zoonosis caused by Leishmania spp., an intracellular protozoan parasite. This parasite is transmitted by sandflies, and the disease is endemic in the Mediterranean basin. In recent years, the number of species which could be a reservoir of the parasite is increased. One of the most relevant species is the horse, due to their contact with humans and ability to control the disease, thus being a possible silent reservoir. In this study, we have analyzed the prevalence and factors related to L. infantum infection in healthy horses in the Mediterranean region. Epidemiological data and serum samples were obtained from 167 apparently healthy horses, and the presence of L. infantum was evaluated via the ELISA method and real-time PCR. The results show 27.5% of prevalence and that the main factors related to infection are equine breed, morphotype, outdoor living, use, and season. In conclusion, the prevalence of L. infantum infection in apparently healthy horses from eastern Spain (Mediterranean basin) is elevated. To control this zoonosis, it would be advisable to carry out more studies on this and other species that could be silent reservoirs of the parasite, as well as carry out measures such as the use of repellents on a regular basis.

Genome-wide copy number variations in Bhutia equine breed using SNP genotyping data

Copy number variants (CNVs) have dynamic potential and evolutionary significance like other genetic variants, namely, single nucleotide polymorphisms, InDels, short tandem repeat polymorphisms, inversion variants, etc. Discovering CNVs leads to further speculation that the genomic DNA contains more changes than previously thought and contributes to the phenotypic variation. CNVs are big DNA fragments (> 1 kb) being duplicated or deleted. A bridge between CNVs and phenotypic variations supports CNVs to be utilized in GWAS, which are currently mostly based on SNPs. CNV, which refers to the structural differences, influence gene expression and can be an indicator of numerous traits for improvement. There is a severe dearth of research on CNVs in animals, especially equine. The present study investigates the genomes of the Bhutia Equine breed for genome-wide discovery of CNVs using theAxiom™ Equine Genotyping Array chip for a better understanding of its traits which had been unexplored till date. A total of 619 CNVs from 20 Bhutia equines were identified with the median and average size as 49.394 kb and 114.955 kb, respectively. Total 225 frequent CNVRs with > 1% CNV frequency were identified among them along with singleton type. These CNVRs contained 361 genes in all. The information obtained on genomic variation could be utilized to identify economically advantageous genetic features in Bhutia equine breed.

Genome-Wide Single-Nucleotide Polymorphism-Based Genomic Diversity and Runs of Homozygosity for Selection Signatures in Equine Breeds.

The horse, one of the most domesticated animals, has been used for several purposes, like transportation, hunting, in sport, or for agriculture-related works. Kathiawari, Marwari, Manipuri, Zanskari, Bhutia, Spiti, and Thoroughbred are the main breeds of horses, particularly due to their agroclimatic adaptation and role in any kind of strong physical activity, and these characteristics are majorly governed by genetic factors. The genetic diversity and phylogenetic relationship of these Indian equine breeds using microsatellite markers have been reported, but further studies exploring the SNP diversity and runs of homozygosity revealing the selection signature of breeds are still warranted. In our study, the identification of genes that play a vital role in muscle development is performed through SNP detection via the whole-genome sequencing approach. A total of 96 samples, categorized under seven breeds, and 620,721 SNPs were considered to ascertain the ROH patterns amongst all the seven breeds. Over 5444 ROH islands were mined, and the maximum number of ROHs was found to be present in Zanskari, while Thoroughbred was confined to the lowest number of ROHs. Gene enrichment of these ROH islands produced 6757 functional genes, with AGPAT1, CLEC4, and CFAP20 as important gene families. However, QTL annotation revealed that the maximum QTLs were associated with Wither's height trait ontology that falls under the growth trait in all seven breeds. An Equine SNP marker database (EqSNPDb) was developed to catalogue ROHs for all these equine breeds for the flexible and easy chromosome-wise retrieval of ROH along with the genotype details of all the SNPs. Such a study can reveal breed divergence in different climatic and ecological conditions.

Genomic inbreeding estimation, runs of homozygosity, and heterozygosity-enriched regions uncover signals of selection in the Quarter Horse racing line.

With the advent of genomics, significant progress has been made in the genetic improvement of livestock species, particularly through increased accuracy in predicting breeding values for selecting superior animals and the possibility of performing a high-resolution genetic scan throughout the genome of an individual. The main objectives of this study were to estimate the individual genomic inbreeding coefficient based on runs of homozygosity (FROH ), to identify and characterize runs of homozygosity and heterozygosity (ROH and ROHet, respectively; length and distribution) throughout the genome, and to map selection signatures in relevant chromosomal regions in the Quarter Horse racing line. A total of 336 animals registered with the Brazilian Association of Quarter Horse Breeders (ABQM) were genotyped. One hundred and twelve animals were genotyped using the Equine SNP50 BeadChip (Illumina, USA), with 54,602 single nucleotide polymorphisms (SNPs; 54K). The remaining 224 samples were genotyped using the Equine SNP70 BeadChip (Illumina, USA) with 65,157 SNPs (65K). To ensure data quality, we excluded animals with a call rate below 0.9. We also excluded SNPs located on non-autosomal chromosomes, as well as those with a call rate below 0.9 or a p-value below 1 × 10-5 for Hardy-Weinberg equilibrium. The results indicate moderate to high genomic inbreeding, with 46,594 ROH and 16,101 ROHet detected. In total, 30 and 14 candidate genes overlap with ROH and ROHet regions, respectively. The ROH islands showed genes linked to crucial biological processes, such as cell differentiation (CTBP1, WNT5B, and TMEM120B), regulation of glucose metabolic process (MAEA and NKX1-1), heme transport (PGRMC2), and negative regulation of calcium ion import (VDAC1). In ROHet, the islands showed genes related to respiratory capacity (OR7D19, OR7D4G, OR7D4E, and OR7D4J) and muscle repair (EGFR and BCL9). These findings could aid in selecting animals with greater regenerative capacity and developing treatments for muscle disorders in the QH breed. This study serves as a foundation for future research on equine breeds. It can contribute to developing reproductive strategies in animal breeding programs to improve and preserve the Quarter Horse breed.

Identification and characterization of single nucleotide polymorphisms in DMRT3 gene in Indian horse (Equus caballus) and donkey (Equus asinus) populations

Equines’ ability in racing and riding as well as gaitedness have influenced the human civilization. Aim of this study was to identify and characterize the novel polymorphisms or SNPs in DMRT3 gene in Indian horse and donkey breeds. In this study, the DMRT3 gene was sequenced and characterized in 72 Indian horses’ and 33 Indian donkeys’ samples. One SNP (A > C) at 878 was found in studied horses while identical SNPs (A > C) at two different nucleotide positions i.e., 878 and 942 in DMRT3 gene (chromosome 23) were observed in studied Indian donkey breeds. Horses and donkeys both have a non-synonymous mutation (A > C) at nucleotide 878 (codon 61) that converts a Stop codon (TAG > TCG) to coding codon Serine, whereas donkeys have a synonymous mutation at nucleotide 942 (codon 82) that converts Serine (TCA > TCC) into Serine. A phylogenetic tree indicated that the DMRT3 gene was equally distributed among the equine breeds. Most of the donkey breeds have been shown high levels of genetic diversity while horse breeds and Halari donkey showed the least genetic diversity. Mutation in DMRT3 has a major impact on gaitedness in horses and is presented at a high frequency in gaited breeds and in horses breed for harness racing.

43 A QTL for skull morphology in Arabian horses

Domestication and selective pressures alter developmental pathways of mammals. The identification of genomic loci for skull morphology in particular can illuminate pathways controlling facial shape. Previous work in the dog identified QTLs for skull morphology and highlighted relationships formed during the development of distinct breeds of dogs from lupine ancestors through the direction of 6 loci across the genome. The Arabian horse is known for its unique concave facial profile in comparison to other equine breeds. We extracted DNA from blood and hair samples for 103 Arabian horses exhibiting diverse skull morphology and genotyped these with the Affymetrix Axiom Equine HD 670k array. Phenotyping was accomplished using 7 defined face measures from a defined protocol and summarized face shape variation using a principal component analysis. Utilizing these 2 principal component scores as skull morphology phenotypes, we performed a genome wide association study using 315,553 SNPs to identify significant preliminary QTLs for the strongest variation in facial morphologywithin this population. We used a linear regression model (PLINK v1.90b6.26) including quality filters for MAF >0.05 and genotyping rate of above 95%. Given the stratification of this population and diversity of subgroups within the Arabian breed, efforts to account for inflation were implemented using the genomic relatedness as a covariate in the linear model. Strong variation in head lengths were noted in the skull principal component 1 phenotype, independent from body size and skull length. Preliminary GWAs identified a promising locus on ECA 5, candidate base pair region: 27,578,838–27,848,837, (raw P = 1.421e-11, Bonferroni corrected P = 1.584e-7) despite strong population stratification across the diverse Arabian breed. Three protein coding genes were noted in this candidate region and further work will investigate these for potentially functional variants and improve phenotype accuracy by applying photo morphometics.

Hematological reference values of horses in Western Libya and their relationship to breed, age, and management.

Hematological evaluation is an important step for health assessment in equine medicine. Besides biochemical tests, that evaluation could be pivotal for diagnosis, prognosis, and treatment monitoring. In Libya, the horse population has drastically increased in the last years, and hitherto, no report addressed the reference hematological values for the existing equine breeds. This study aimed to establish the reference for hematological indices of traditional equestrian and stud-farm equine breeds in Western Libya in regard to some variables such as individual characteristics, management system, and rearing purpose. Blood samples of 167 horses of Arabian, Thoroughbred, and local breeds were collected from an area covering a large part of Western Libya and complete blood counts of the samples were performed using a hematological auto-analyzer. The collected data were statistically analyzed using the Statistical Package for Social Science software. Hematological reference indices were generated for the aforementioned equine breeds in Western Libya. The equine hematological profile was variable according to some individual and management factors. In addition, the significant effects of those factors were usually restricted to erythrocyte- and platelets (PLTs)-related indices. In terms of breed influence, Thoroughbreds had significantly lower erythrocyte counts of red blood cells (RBCs) compared to local horses (p = 0.04), and Arabian horses showed significantly higher PLT counts compared to Thoroughbreds and local horses; p = 0.00 and p = 0.03, respectively. Moreover, significantly lower values of hemoglobin (HGB), hematocrit (HCT), mean cell volume (MCV), and PLT counts were noticed in young horses vis-à-vis significantly higher values of HCT, mean corpuscular hemoglobin concentration and red cell distribution width in females. In regard to exercise, racing horses varied significantly from nonracing horses in monocyte percentage (p = 0.04), RBC (p = 0.00), HGB (p = 0.00), HCT (p = 0.00), MCV (p = 0.00), and mean corpuscular hemoglobin (MCH) (p = 0.00). Diet supplementation also influenced the equine erythrocyte-related indices, as horses offered supplemented diet had significantly higher RBC (p = 0.00), HGB (p = 0.00), HCT (p = 0.00), MCV (p = 0.00), and MCH (p = 0.00), comparing to those served nonsupplemented diet. This study provided the first reference values of the equine hematological profile in Western Libya. In addition, the age, breed, exercise, and diet supplementation had variable impacts on hematological equine indices.

The influence of foreign lineages in the genetic component of reproductive traits in Criollo Argentino mares: A 30-year study

The Criollo horse is the most important equine breed in Argentina. These horses are characterized by their strength, resistance, and increased fertility even at old ages, and they are also associated with Argentine tradition and livestock heritage. However, over the last 70 years, the Criollo Argentino breed has been influenced by other South American Criollo horses from Brazil, Uruguay, or Chile. In this study, we aimed to determine the genetic influence of foreign individuals on the reproductive performance of Criollo Argentino mares. To achieve this, we analyzed a large dataset including pedigree records of nearly 212,000 individuals. For the analysis, the individuals were organised into clusters based on their genetic origin (foreign or native Criollos). We then performed a comprehensive genetic characterization of each group, as well as an estimation of the estimated breeding values (EBVs), heritabilities, and genetic correlations for the three traits, using a multi-trait mixed model. Our results demonstrate a positive trend toward the introgression of foreign breeding lineages in the Criollo Argentino population. However, we also quantified a low-to-moderate genetic influence on all the fertility traits analysed, and the absence of any negative effect associated with inbreeding. Despite the fact that the genetic origin produced certain differences between foreign and native individuals in terms of fertility at the beginning of the study, the use of foreign lineages did not significantly change the fertility of the Criollo Argentino mares. To our knowledge, this is the first study analysing the fertility of Criollo horses from a genetic point of view.

Timing of Vertical Head, Withers and Pelvis Movements Relative to the Footfalls in Different Equine Gaits and Breeds.

Knowledge of vertical motion patterns of the axial body segments is a prerequisite for the development of algorithms used in automated detection of lameness. To date, the focus has been on the trot. This study investigates the temporal synchronization between vertical motion of the axial body segments with limb kinematic events in walk and trot across three popular types of sport horses (19 Warmbloods, 23 Iberians, 26 Icelandics) that are known to have different stride kinematics, and it presents novel data describing vertical motion of the axial body segments in tölting and pacing Icelandic horses. Inertial measurement unit sensors recorded limb kinematics, vertical motion of the axial body at all symmetrical gaits that the horse could perform (walk, trot, tölt, pace). Limb kinematics, vertical range of motion and lowest/highest positions of the head, withers and pelvis were calculated. For all gaits except walk and pace, lowest/highest positions of the pelvis and withers were found to be closely related temporally to midstance and start of suspension of the hind/fore quarter, respectively. There were differences in pelvic/withers range of motion between all breeds where the Icelandic horses showed the smallest motion, which may explain why lameness evaluation in this breed is challenging.

Genetic diversity and population structure of locally adapted Brazilian horse breeds assessed using genome-wide single nucleotide polymorphisms

Animals first introduced in Brazil with the discovery were submitted to various selective pressures over five centuries, developing adaptive traits specific to the hostile environments found in the country. A high quantity of genotypic information can be generated quickly and with high repeatability and reliability using genome-wide Single Nucleotide Polymorphism (SNP) panels. Blood samples from 285 horses belonging to eight Brazilian breeds (Baixadeiro, Lavradeiro, Marajoara, Puruca, Campeiro, Crioulo, Mangalarga Marchador and Pantaneiro) and two commercial breeds sampled in Brazil (Arabian and English Thoroughbred) were genotyped focusing on elucidating the genetic structure and composition within and among Brazilian horse breeds and some of their possible founders. Data from the GGP Equine BeadChip (GeneSeek® Genomic Profiler™ Equine, 65.157 SNPs) was used to assess basic diversity parameters, genetic distance (pairwise FST and Nei), Principal Component Analysis (PCA), Analysis of Molecular Variance (AMOVA) and population structure (ADMIXTURE). Results showed that Crioulo (few animals), Pantaneiro, Mangalarga Marchador, and Campeiro breeds possess distinct genetic bases from the others and each other. The Lavradeiro, Baixadeiro, Puruca, and Marajoara breeds have a shared genetic basis, hindering their differentiation. The results also reflected a geographic division of the Brazilian equine breeds, with those originally from the North and Northeast regions (Lavradeiro, Marajora, Puruca and Baixadeiro) grouped. On the other hand, animals from the South and Southeast regions (Crioulo, Campeiro and Mangalarga Marchador) were genetically closer although distinguished. The Pantaneiro breed originating from Pantanal Matogrossense in the Midwest region of Brazil, separated from all the others. Overall, high values of genetic variability and low values of FIS were observed for the Brazilian naturalized breeds. Both Arabian and English Thoroughbred sampled in Brazil presented a similar genetic variability to the Brazilian breeds but were genetically differentiated. This study aims to understand better the genetic variability and relation among Brazilian naturalized horse breeds and their possible origins. This information helps establish and maintain conservation nuclei and programs for each horse breed. Results found here can be used as a base for backup decisions regarding management to optimize conservation programs and other support sampling strategies for the National Animal Germplasm Program.

Detection of Common Copy Number of Variants Underlying Selection Pressure in Middle Eastern Horse Breeds Using Whole-Genome Sequence Data

Dareshouri, Arabian, and Akhal-Teke are 3 Middle Eastern horse breeds that have been selected for endurance and adaptation to harsh climates. Deciphering the genetic characteristics of these horses by tracing selection footprints and copy number of variations will be helpful in improving our understanding of equine breeds' development and adaptation. For this purpose, we sequenced the whole genome of 4 Dareshouri horses using Illumina Hiseq panels and compared them with publicly available whole-genome sequences of Arabian (n = 3) and Akhal-Teke (n = 3) horses. Three tests of FLK, hapFLK, and pooled heterozygosity were applied using a sliding window (window size = 100 kb, step size = 50 kb) approach to detect putative selection signals. Copy number variation analysis was applied to investigate copy number of variants (CNVs), and the results were used to suggest selection signatures involving CNVs. Whole-genome sequencing demonstrated 8 837 950 single-nucleotide polymorphisms (SNPs) in autosomal chromosomes. We suggested 58 genes and 3 quantitative trait loci, including some related to horse gait, insect bite hypersensitivity, and withers height, based on selective signals detected by adjusted P-value of Mahalanobis distance based on the rank-based P-values (Md-rank-P) method. We proposed 12 genomic regions under selection pressure involving CNVs that were previously reported to be associated with metabolism energy (SLC5A8), champagne dilution in horses (SLC36A1), and synthesis of polyunsaturated fatty acids (FAT2). Only 10 Middle Eastern horses were tested in this study; therefore, the conclusions are speculative. Our findings are useful to better understanding the evolution and adaptation of Middle Eastern horse breeds.

Modularity among horse mandibles: a study in the Araucan breed

ABSTRACT The concepts of integration and modularity refer to the degree of covariation between the components of a biological structure. Components that covariate strongly, but are relatively independent of other modules, are called morphological modules. Morphological integration is understood as the coordinated morphological variation of these components as a functional unit. In mandible case, four modules have been defined based on their differential embryonic origin: alveolar, basal body, coronoid and condylar. The aim was to test these four modular mandible bases using geometric morphometric techniques. The hypothesis of modularity of mandibular development, based on differential embryonic origins, was tested using digital pictures of hemimandibles in lateral form from 26 Araucan horses for those modules. Subsequently, the level of morphological integration between the modules defined above was evaluated using eight landmarks and 65 semi-landmarks, through an analysis of paired blocks of least squares. The divisions between those units presented a modular foundation and the respective level of morphological integration between all considered units. The results of our modular and integrative analysis can be very useful for the comparative study of adaptive processes of other equine breeds.