Horse Breeds Research Articles

Multiple Trait Bayesian Analysis of Partitioned Genetic Trends Accounting for Uncertainty in Genetic Parameters. An Example With the Pirenaica and Rubia Gallega Beef Cattle Breeds.

Genetic trends are a valuable tool for analysing the efficiency of breeding programs. They are calculated by averaging the predicted breeding values for all individuals born within a specific time period. Moreover, partitioned genetic trends allow dissecting the contributions of several selection paths to overall genetic progress. These trends are based on the linear relationship between breeding values and the Mendelian sampling terms of ancestors, enabling genetic trends to be split into contributions from different categories of individuals. However, (1) the use of predicted breeding values in calculating partitioned genetic trends depends on the variance components used and (2) a multiple trait analysis allows accounting for selection on correlated traits. These points are often not considered. To overcome these limitations, we present a software called "TM_TRENDS." This software performs a Bayesian analysis of partitioned genetic trends in a multiple trait model, accounting for uncertainty in the variance components. To illustrate the capabilities of this tool, we analysed the partitioned genetic trends for five traits (Birth Weight, Weight at 210 days, Cold Carcass Weight, Carcass Conformation, and Fatness Conformation) in two Spanish beef cattle breeds, Pirenaica and Rubia Gallega. The global genetic trends showed an increase in Carcass Conformation and a decrease in Birth Weight, Weight at 210 days, Cold Carcass Weight, and Fatness Conformation. These trends were partitioned into six categories: non-reproductive individuals, dams of females and non-reproductive individuals, dams of sires, sires with fewer than 20 progeny, sires between 20 and 50 progeny, and sires with more than 50 progeny. The results showed that the main source of genetic progress comes from sires with more than 50 progenies, followed by dams of males. Additionally, two additional features of the Bayesian analysis are presented: the calculation of the posterior probability of the global and partitioned genetic response between two time points, and the calculation of the posterior probability of positive (or negative) genetic progress.

Bayesian Recursive and Structural Equation Models to Infer Causal Links Among Gait Visual Scores on Campolina Horses.

Gait visual scores are widely applied to horse breeding because they are a fast and easy phenotyping strategy, allowing the numeric interpretation of a complex biological process such as gait quality. However, they may suffer from subjectivity or high environmental influence. We aimed to investigate potential causal relationships among six visual gait scores in Campolina horses. The data included 5475 horses with records for at least one of the following traits: Dissociation (Di), Comfort (C), Style (S), Regularity (R), Development (De), and Gait total Scores (GtS). The pedigree comprised three generations with 14,079 horses in the additive relationship matrix. Under a Bayesian framework, (co)variance components were estimated through a multitrait animal model (MTM). Then, the inductive causation algorithm (IC) was applied to the residual (co)variance matrix samples. The resulting undirected graph from IC was directed in 6 possible causal structures, each fitted by a structural equation model. The final causal structure was chosen based on deviance information criteria (DIC). It was found that S significantly impacts the causal network of gait, directly and indirectly affecting C. The indirect causal effect of S on C was through the direct effect of S on De, then the direct effect of De on R, and finally, the direct effect of R on C. Di was caused by S, which is the reason for the genetic correlation between Di and GtS, due to causal effects being added to the model, they absorb the genetic correlation between Di and GtS. Those paths have biological meaning to horse movements and can help breeders and researchers better understand horses' complex causal network of gait.

Genetic Composition of Polish Hucul Mare Families mtDNA Diversity

Backround: The Hucul horse breed formed in the region of the Eastern Carpathians, likely through the natural crossbreeding of oriental horses. After World War II, their population significantly decreased, leading to the breeding being based on only 14 female lines, whose founders often had unknown origins. To preserve the breed’s unique characteristics, it is now part of a Genetic Resources Conservation Program, which prioritizes the maintenance of genetic diversity. This study aims to clarify the maternal relatedness of founder mares and assess genetic diversity using mitochondrial DNA (mtDNA). Methods: The hyper-variable region of the mitochondrial genome was analyzed in 57 horses. Pedigree records were used to trace genealogical lines, and molecular analysis focused on identifying maternal relationships between founder mares. Results: The analysis revealed close maternal kinships between the lines of Jagoda and Bajkałka, as well as Sekunda and Sroczka. In the Hucul population, seventeen mitochondrial haplotypes were identified, with three that did not match any established lines. The findings reveal discrepancies between pedigree records and mitochondrial DNA data, suggesting potential inaccuracies in the Hucul horse studbook. Conclusions: The findings highlight the importance of combining pedigree and molecular data to refine strategies to preserving genetic diversity, minimizing inbreeding, and improving the management the Genetic Resources Conservation Program.

Our employees in traditional and environmentally friendly logging: characteristics of forestry workhorses in Hungary

ABSTRACT Horse logging has many advantages over forestry machines, but it is less efficient, mainly depending on the breed and size of the horse. After reviewing the literature on the state and breeds of horses used for timber harvesting in Europe, we recorded the sex, age, height at withers (where the neck meets the back), girth size and shank circumference of the workhorses in the Hungarian state forests. Most loggers (37%) used crossbreeds of warm-blooded and cold-blooded horses, because of their pace, smaller size and easier maneuverability. Twenty-nine percent of the loggers used the Muraközi type, 14% the French cold-blooded (Percheron), and 11% the Hungarian cold-blooded. The reason for using cold-blooded types was their capacity, calmness, resistance and rare foot injuries. The disadvantages of the crossbreds were their speed and lighter size. Comparing the size of the horses assessed in the field with the literature data on the breeds, it is not possible to draw clear conclusions as to which breed would be more suitable for forestry work. Most (59%) of the horses used for logging are geldings, as they are reported to be easier to work with. Forestry use could play an important role in maintaining the population of the protected indigenous horse breeds, both Hungarian cold-blooded and Muraközi.

Comparison of the fine structure of hair in the ancient Lena horse (†Equus lenensis Russanov 1968) and the domestic horse (Equus caballus caballus Linnaeus 1758) of native northern breeds

Using SEM and morphometry, the fine structure of guard hairs and the elements of their medulla were compared in the Lena horse (Equus lenensis) and the domestic horse (E. caballus caballus) of five breeds. A number of features of hair fine structures have been identified, most clearly revealed when comparing horses of the northern (Mezen, Pechora, Yakut) and southern (Arabian, Akhal-Teke) groups of breeds. Seasonal changes in the structure of hair in horses of northern breeds (thickening of the hair medulla and an increase in the volume of its air cavities) indicate an increase in the heat-protecting properties of wool in winter, this being of adaptive significance. Both Pleistocene and recent domestic horses are shown to have developed convergent morphological adaptations of wool to low air temperatures.

Hungarian Count, the Polish Major and the Slovenian War Horses in South Africa

The noble Hungarian Jankovics-Bésán family have long being renowned as influential breeders of Lipizzan horses. During the Second World War in 1944 with the advancing Soviet Red Army bearing down on the family stud farm then located at Oreglak in Hungary, Count Elemér Janković-Bésán de Pribér-Vuchin, decided to flee the farm. He, however, refused to leave behind his beloved horses and fled with eight of the animals, two stallions and six mares. After stops in Germany and England, the Count decided to relocate with his horses to the Natal midlands of South Africa, where he re-established his family stud farm. In 1951, during the Royal Agricultural Show in Pietermaritzburg, KwaZulu-Natal, South Africa, the Hungarian horse breeder by chance met a Polish horse trainer. Major Jerzy (George) Iwanowski (13 March 1907 – 28 May 2008) was a graduate of the College of Agriculture in Warsaw. After the Second World War, Iwanowski also decided to leave Europe and relocate to South Africa, where he established the Centaur Stables in Johannesburg. It is from this meeting of two European horse lovers on the rolling hills of KwaZulu-Natal that South Africa’s world-famous Lipizzaner horses are derived. Based exclusively on the high standards as established by the Spanish Riding School based in Vienna, Austria, South African Lipizzaner’s have been performing since 1957. The original riders were almost exclusively women, unlike their European counterparts. This was because in South Africa the Lipizzan horses that formed part of the original performing team were all privately owned by women who were able to donate their time and efforts to a non-profit organisation that did not really pay its riders to perform.

Repellent activity of icaridin-impregnated horsecloth against horse flies

Horseflies are pests that cause discomfort from blood-sucking and disease transmission, and economic losses in the equine industry. This study evaluated the efficacy of horsecloth impregnated with icaridin in reducing horsefly attacks and deterring horseflies. Repellent activities were evaluated under three conditions: treatment 1 (no horsecloth), 2 (horsecloth without icaridin), and 3 (horsecloth impregnated with icaridin), using three native Hokkaido horses (Dosanko) and three mixed-breed horses (Dosanko and Haflinger) in July 2023 at a riding horse club in Hokkaido, Japan. Treatment 3 significantly reduced the number of horseflies. Treatment 2 did not significantly reduce horsefly numbers. Treatments 2 and 3 significantly reduced the number of avoidance actions. The reduction in avoidance actions in treatment 3 was greater than that in treatment 2. Lighter-colored horses experienced fewer fly attacks and avoidance actions than darker-colored horses. Overall, using icaridin-impregnated horsecloths (treatment 3) was more effective for repelling horseflies than the use of physical barriers alone (treatment 2). This study suggests that integrating chemical repellents with physical protection can enhance horsefly control strategies, improve horse welfare, and improve the safety of horses interacting with them. Further research is recommended to assess the generalizability of these findings to different horse breeds and environments with a greater number of horses.

Analysis of the Genetic Structure of 29 Horse Breeds of Russian Selection by str Markers

The current stage of genetic certification of horses of factory and local breeds based on microsatellite analysis makes it possible to quite effectively carry out identification and genetic examination of the origin of breeding animals, as well as solve the problem of assessing and preserving genetic resources. With a reduction in the number of breeding stock to 200–300 mares, observed in a number of breeds, the threat of a decrease in the genetic diversity of populations and the accumulation of genetic load increases, which necessitates the need to study and monitor the genetic structure of horse breeds. In this regard, our comparative genetic analysis of polymorphism of 17 microsatellite loci in 20541 horses of 30 factory and local breeds allows us to certify the basic part of the genetic resources of the horse breeding of the Russian Federation. including riding, trotter, draft and local breeds. During the genetic population analysis of the studied breeds, basic parameters were assessed: the total number of allele variants (Na), the effective number of alleles (Ae), the average number of alleles per locus (MNA), the level of observed (Ho) and expected heterozygosity (He), as well as the coefficient of intrapopulation inbreeding Fis. Phylogenetic relationships of breeds were assessed using the R and R Studio software packages. Among horse breeds of different specializations, the highest values of all indicators of genetic diversity (Ae, Ho, He and Na) were determined in aboriginal populations. In the allele pool of local horse breeds, there were rare alleles ASB2T, HMS7S, HMS6J, HMS6H, HMS2T, HMS1O, HTG7L, HTG6L, HTG6H, VHL20S, ASB17Z, ASB17X, ASB17U, LEX3S, LEX3R and CA425E, which were absent in horses of factory breeds. Among the riding horse breeds created in Russia, the Budennovsk, Don and Kabardian horse breeds stood out due to the presence of rare alleles. Alleles ASB2G, ASB2F, HMS2F, HTG7Q and ASB23O were found in trotter horses, which were not identified in the genetic structure of other breeds. The phylogenetic analysis showed the division of horse breeds into two clear subclusters, the first of which included only factory breeds. The second cluster united all the native breeds, as well as the Orlov trotter and a group of draft breeds, which were used for many years as improvers of the local horse population. The analysis of the genetic structure of domestic horse breeds revealed a fairly high reserve of diversity even in small populations, which is an indispensable condition for successful selection in horse breeding.

Thyme oil and argan oil's effects on horse welfare

This study examines the effectiveness of thyme oil and argan oil as potential treatments for leg edema in horses. Swollen legs, often a result of infections, injuries, allergies, and underlying health conditions can significantly affect a horse's mobility and overall health. Traditional treatments may include antibiotics, anti-inflammatories, cold therapy, compression bandaging, and rest, but there is growing interest in natural remedies. For this purpose, argan and thyme oil were applied to 22 horses of various ages and different breeds at different times at Mersin Doğa Horse Farm. As a result of the study, some observations before and after the application of thyme and argan oil are listed. In addition, there was a significant association between oils and side effect from rash, itchiness, temperature increase, drinking too much, excessive urination (p

The global spread of Oriental Horses in the past 1,500 years through the lens of the Y chromosome

Since their domestication, horses have accompanied mankind, and humans have constantly shaped horses according to their needs through stallion-centered breeding. Consequently, the male-specific portion of the Y chromosome (MSY) is extremely uniform in modern horse breeds. The majority of stallions worldwide carry MSY haplotypes (HT) attributed to an only ~1,500-y-old, so-called, "Crown" haplogroup. The predominance of the Crown in modern horse breeds is thought to represent a footprint of the vast impact of stallions of "Oriental origin" in the past millennium. Here, we report the results of a fine-scaled MSY haplotyping of large datasets of patrilines comprising 1,517 males of 189 modern horse breeds, covering a broad phenotypic and geographic spectrum. We can disentangle the multilayered influence of Oriental stallions over the last few hundred years, exposing the intense linebreeding and the wide-ranging impact of Arabian, English Thoroughbred, and Coldblood sires. Iberian and New World horse breeds contain a wide range of diversified Crown lineages. Their broad HT spectrum illustrates the spread of horses of Oriental origin via the Iberian Peninsula after the Middle Ages, which is commonly referred to as the "Spanish influence." Our survey also revealed a second major historical dissemination of horses from Western Asia, attributed to the expansion of the Ottoman Empire. Our analysis shows that MSY analysis can uncover the complex history of horse breeds and can be used to establish the paternal ancestry of modern horse breeds.

Clinical and epidemiological aspects in equine aural plaques.

The association between aural plaques, Equus caballus papillomavirus (EcPV), and the different breeds of horses and risk factors is poorly described. The objective of this study was to determine the clinical prevalence of aural plaques in Mangalarga Marchador (MM) and Quarter Horse (QH) horses in Brazil, to evaluate the association of this prevalence with some risk factors, and to detect the presence of EcPV DNA (types 1-10) in aural plaques biopsies. A total of 400 MM and 425 QH horses, were clinically evaluated. For each horse, an identification form was completed, containing information on breeding, sex, age, presence, and classification of aural plaque lesions, presence of ectoparasites, management type, ear clipping performed, and sensitivity to ear palpation. Biopsies of the lesions were taken from 30 horses and assessed for the presence of EcPV DNA using PCR. Among the MM and QH horses evaluated, 41.5% and 33.6%, respectively, had aural plaques. The MM horses showed a higher frequency of plaques than QH (p = 0.02). At least one viral type was identified in 90% of all aural plaque biopsies, with EcPV4 being the most frequently detected in both breeds, followed by EcPV6, EcVP5, EcVP3 and EcPV1 respectively. In one sample, EcPV1 was detected alone, although it had previously been described only in copresence. The copresence of viral DNA the MM 73% (11/15) QH 27% (4/15) horses. Aural plaques are widely distributed, with a higher prevalence of EcPV4. Additionally, MM horses have higher susceptibility and frequency of the disease than QH horses.

A survey of ocular pathology in Warmblood horses in South Africa.

Warmblood horses are a popular breed around the world for equestrian sports. Previous studies have investigated ocular findings in other breeds of horses; however, no studies exist for the Warmblood breed. To determine the prevalence of ocular abnormalities in a convenience sample of Warmblood horses in South Africa and to determine if the prevalence of lens and chorioretinal lesions increase with age. Descriptive, observational study. Warmblood horses underwent a full ophthalmic examination which included a Schirmer tear test (STT), tonometry, fluorescein dye testing, slit lamp biomicroscopy and indirect ophthalmoscopy. Age was categorised into three groups namely <8 years old, 8-13 years old and 14+ years old for statistical analysis. Prevalence of lens and chorioretinal lesions were compared between age categories. One hundred and four horses (208 eyes) were examined. The age range was 5 months to 30 years (mean 11 years, standard deviation [SD] 6 years). Ocular pathology was noted in 125 eyes (60.1%) and 79 horses (76%). The highest number of lesions were noted in the choroid and retina, iris and lens. Chorioretinal lesions were seen in 100 eyes (48.1%) and in 65 horses (62.5%). Iridial lesions were seen in 19 eyes (9.1%) and 12 horses (11.5%). Cataracts were seen in 19 eyes (9.1%) and in 13 horses (12.5%). The presence of total chorioretinal lesions (eye level [p = 0.002]; horse level [p = 0.004]), focal chorioretinal lesions (eye level [p = 0.004]; horse level [p = 0.008]) and cataract (eye [p = 0.03]; horse level [p = 0.02]) were all shown to statistically increase with age. A small sample size and limited geographic area. There was a high prevalence of ocular pathology in this population of Warmblood horses in South Africa. This reiterates the importance of an ocular examination as a part of routine health checks, as well as during prepurchase examinations.

Activated charcoal application in gastric ulceration areas in horses: preliminary experimental study

Gastric ulceration is frequent in adult horses, bringing significant economic and welfare implications to these animals. Treatment may employ several drugs, but adsorbents, such as activated charcoal, are not mentioned. Activated charcoal may be a valuable therapeutic option mainly because of its few adverse effects, fecal elimination, and low cost. This study aimed to evaluate the use of activated charcoal in experimentally induced gastric ulceration in horses and perform the microscopic characterization of charcoal particles in the injured epithelium. Five adult, undefined breed horses underwent a gastric ulcer induction protocol based on alternating fasting and free food access periods. Next, we performed a gastroscopic examination and applied activated charcoal diluted in water at the ulcers through a probe passed through the working channel of the gastroscope. The gastric mucosa was washed with water after a contact period of 5 min until the complete lack of macroscopic product visualization. Then, we performed a biopsy of the aglandular mucosa in erosive to ulcerative injury sites and a microscopic assessment of the fragments. Macroscopically, all animals presented ulcerative lesions in the greater or lesser gastric curvature along the margo plicatus and hyperkeratosis in the aglandular portion. Microscopically, all animals had hyperplasia, hyperkeratosis, epithelial erosion, desquamated epithelial cells, inflammatory cells, and variable amounts of charcoal particles, either free or adhered to the epithelium. We concluded that activated charcoal remains adhered to aglandular gastric lesions in horses even after lavage with water and histological processing, allowing its microscopic visualization. Therefore, activated charcoal’s effectiveness as a therapy for equine gastric lesions warrants evaluation.

Zootechnical characteristics of the emerging lines of stallions of the Yakut breed in the Oymyakonsky ulus of Yakutia

Purpose: zootechnical characteristics of the developing lines of Yakut breed stallions in the breeding farm "Agricultural production cooperative "Tonor" of the Oymyakon ulus of Yakutia.Materials and methods. The study of the exterior indicators of the stallions was carried out by taking body measurements according to the instructions of the All-Russian Research Institute of Horse Breeding. The use of genotypic assessment methods for animals along with classical zootechnical assessment methods for pedigree, productive traits (live weight and meat productivity of offspring, milk production, fertility of daughters) was supplemented by the use of the method of selecting offspring based on their adaptability to herd conditions.Results. Long-term selection work in the breeding farm of the Oymyakon ulus is completed by the formation of six lines of outstanding Yakut breed stallions. In terms of live weight, both stallions and mares of the Oymyakon horse surpass stallions and mares of the Yana, Kolyma and indigenous types. Oymyakon stallions (n=20) weighed on average 483,7±3,55 kg, while stallions of the indigenous types weighed 446,3±4,75 kg (n=34), Kolyma types 449,1±3,42 kg (n=87) and Yana types 469,4±3,27 kg (n=128). Oymyakon horse mares (n=165) also surpassed mares of the indigenous type (401,6±2,00 kg (n=341)), Kolyma type (432,2±1,13 kg (n=1063) and Yang type (431,0±1,16 kg (n=881)) in average live weight of 453,8±2,19 kg. According to measurements of head, neck, chest, croup, occiput and withers, chest and croup width and their indices, Oymyakon horse stallions and mares are practically no different from indigenous type horses. The founder of the line with the most numerous followers is the outstanding stallion Kyurzhet, born in 1946. He came from local Yakut horses of the former Bolshevik collective farm. His line continues on the Tonor farm through his two descendants: his grandson Chalay, born in 1981, live weight 515 kg, and his great-grandson Tenkelekh, born in 1992, live weight 490 kg. The farm produced Kyurzhet's great-great-great-grandson Chalay and 6 great-great-great-great-grandchildren, and now produces 11 continuers of the line (3 great-great-great-great-grandchildren and 8 great-great-great-great-great-grandchildren), a total of 18 continuers of his line have been and are being produced.

Molecular and morphofunctional bases of development of the horse multiple congenital eye anomalies with the silver gene presence on the example of the &lt;i&gt;Soviet draft&lt;/i&gt; breed

The article concretizes clinical data on the molecular and morphofunctional foundations of the development of multiple congenital eye abnormalities (MСOA) linked to the silver gene, using the example of the Soviet heavy-duty horse breed. Recommendations for owners on their maintenance and medical support and work with them are provided. The study was conducted on the basis of data from the VNIIK breeding center for the specified horse breed, genetic testing and ophthalmological examination. The focus group included 26 horses of the Soviet heavy-duty breed, examined for the presence of the silver gene. The results of the study showed that horses of the Soviet heavy-duty breed should undergo genetic testing for the presence of a silver gene in the genotype. However, the presence of MCOA linked to the silver gene is not an indication for the culling of horses due to the status of this breed as endangered, if it is necessary to select a mate for mating without genetic abnormalities so that they do not spread during uncontrolled crossing. Regular observation of an ophthalmologist and strict implementation of his recommendations are necessary to prevent the development of infectious complications and rapid progression of the disease with the onset of blindness. Horses homozygous for the silver gene should be kept in conditions that limit the possibility of injury to the eyeballs, including secondary damage to eye structures by the UV spectrum of solar radiation, for which translucent/opaque masks or sunglasses should be used. Working on homozygous horses with partial or complete loss of vision is potentially dangerous and possible only if a number of conditions are met and the owner is ready to bear legal responsibility for possible consequences.

Prostaglandin use in broodmares. Part 2: other applications in reproduction

Prostaglandins are essential medications used in equine reproduction, and the author has explored physiology, safety and some clinical applications in the first of this two-part article series. This second part focuses on reported applications of prostaglandins in other areas of reproduction related to the broodmare. These include termination of pregnancy and examining protocols to be used depending on the stage of gestation. Infertility and treatment related to presumed oviductal blockage, foal fostering and treatment of foal rejection are described. This article also examines the effects of prostaglandins on the uterus and cervix, and their possible uses in clinical practice relating to uterine fluid accumulation and infection. The uses of prostaglandins in broodmare reproduction are numerous, although the mechanism of effect is not always clear and, in some cases, scientific evidence can be inconclusive. However, they still represent one of the most frequently used drugs in this subspecialty.

It's a thoroughbred career for this equine vet!

Standing still wasn't an option for Meta Osborne and she started her race to the top of the equine reproduction game soon after graduating from University College Dublin and gaining experience in the USA.

The expansion of British steeplechasing in the Grand Duchy of Posen

ABSTRACT In the nineteenth century, British culture and sport were held in high esteem abroad as models of progress and modernity. British-organised sports gained prestige in European societies, and their practice became a symbol of social class development and progress. In contrast to the Polish population living under Austrian and Russian rule, the Polish population of the Prussian-controlled Grand Duchy of Posen had the opportunity to practise, or at least passively enjoy, steeplechasing, which originated in the British Isles. This was made possible by the Society for the Improvement of Horse, Cattle and Sheep Breeding in the Grand Duchy of Posen. Unlike the British steeplechase, the Society's jump races were free of betting and focused more on utilitarian aspects by promoting the improvement of horse breeding and the benefits of horse ownership. Despite the socio-political differences, they were very similar to their British counterparts. This makes the steeplechase races in the western Polish territories annexed by Prussia significant events and, in some ways, pioneering contributions to the development of the sport in Continental Europe. With the establishment of English sporting fashions, the steeplechase became one of the components of a long-term process of introducing various British sports to Poland.

IVF with frozen-thawed sperm after prolonged capacitation yields comparable results to ICSI in horses: A morphokinetics study

Intracytoplasmic sperm injection (ICSI) is the current clinical practice for the in vitro production of equine embryos. The use of conventional fertilization methods such as in vitro fertilization (IVF), has historically been associated with poor success in horses. However, recent improvements have led to better outcomes with IVF, though only when using fresh semen, which limits its use in clinical practice. IVF remains in its infancy in equine reproduction, and several unknowns remain about the technique. One significant gap in knowledge concerns the morphokinetics of IVF embryos and how they differ from their ICSI counterparts. To address this, we performed IVF using frozen-thawed sperm from five different stallions following sperm selection and a prolonged capacitation period of 10 h, on a total of 109 oocytes. We then analyzed the cleavage rate (cleaved/initial oocytes), blastocyst rate (blastocyst/initial zygotes), and blastocyst development (blastocyst/cleaved zygotes) of the IVF cycles, and compared them with those of the clinical ICSI cycles during the same period. We also evaluated time-lapse images of the developed embryos to assess developmental time points such as time to morula compaction and blastocyst expansion, as well as morula and blastocyst sizes. Overall, developmental rates were not different between IVF and ICSI cycles (blastocyst rate 41.1 % IVF and 41.8 % ICSI, p > 0.05). However, development proceeded faster in IVF cycles (blastocyst expansion IVF 155.5 ± 18.5 h; ICSI 167.2 ± 19.6 h; p < 0.05) and IVF embryos were also larger (blastocyst area IVF 22608 ± 2857 μm2; ICSI 20806 ± 1505 μm2; p < 0.05). The faster development and larger size might suggest a more advanced developmental stage. The implications of these findings need to be further evaluated to assess their association with pregnancy potential. The successful developmental rates achieved in IVF cycles demonstrate the potential of this technique for clinical application, although the amount of frozen-thawed semen required is significantly higher in IVF than in ICSI, which is an important consideration for mare and stallion owners. Nonetheless, the use of frozen-thawed semen in equine IVF, coupled with comparable blastocyst rate, presents promising potential for broader clinical adoption of the IVF technique.

Genomic insights into the genetic diversity, lateral gaits and high-altitude adaptation of Chakouyi (CKY) horses

Chakouyi (CKY) horses from the Qinghai‒Xizang Plateau are well known for their unique lateral gaits and high-altitude adaptation, but genetic mechanisms underlying these phenotypes remain unclear. This study presents a comparison of 60 newly resequenced genomes of gaited CKY horses with 139 public genomes from 19 horse breeds. Population structure analyses (admixture, PCA, and neighbor-joining tree) reveal a close genetic relationship between CKY and other highland breeds (Tibetan and Chaidamu horses). Compared with other Chinese breeds, CKY horses present reduced nucleotide diversity (θπ) and lower inbreeding (FROH coefficient), suggesting possible selective pressures. A key region on chromosome 23 (Chr23: 22.3–22.6 Mb) is associated with the lateral gaits and harbors a highly prevalent nonsense mutation (Chr 23: 22,391,254 C > A, Ser301STOP) in the DMRT3 gene, with an 88% homozygosity rate, which is strongly correlated with the distinctive gait of CKY horses. Furthermore, selection signals reveal that the EPAS1 gene is related to high-altitude adaptation, and the CAT gene contributes to altitude resilience in CKY horses. These findings suggest that preserving genetic diversity is essential for maintaining the unique gaits and high-altitude adaptations of CKY horses.