Horse Breeds Research Articles

Patron versus Painter: Portrait Commissions and the Colonial Art Market

In April 1854 the artist James Shaw took a patron, horse breeder Henry Woodhead, to court claiming damages. His patron, Shaw argued, had received the commissioned artwork, a portrait of his prize-winning draught horse ‘Warwick’, but refused to pay for it. An investigation of this case and of Justice Cooper’s judgement – not completely satisfying to either party – provides new insights into the position of artists in the art market in mid-nineteenth-century Adelaide. Portraits, or ‘likenesses’ as they were often called, were generally the most commercially lucrative sales for artists, and yet these commissions could expose shortcomings in the colonial art market. Embracing innovative strategies in soliciting patronage and developing their artistic activity, artists often found themselves grappling with a collision of consumer interests, market frailty, and the shifting codes of Victorian taste.

People and horses in the Late Roman Period - Late Migration Period (3rd-7th centuries) in Lithuania: origins and social context

This paper presents a study analysing the mobility and possible immigration of humans and horses in Lithuania in the Late Roman Period – Migration Period (3rd–7th centuries AD), based on 87Sr/86Sr stable isotopes analysis. During the study, we carried out strontium analysis of 40 human teeth from 11 burial sites and 13 horses from six burial sites. In addition, to reconstruct bioavailable 87Sr/86Sr ranges, we analysed 87Sr/86Sr of 41 animals from 15 prehistoric and historic sites. A human sample was collected to evaluate the presumed immigration directions and mobility of both sexes, different social groups, and in different regions of Lithuania. Stable isotope analysis, radiocarbon dating, biometric measurements, and other studies have provided new insights into the origins, mobility, and other aspects of lifestyle and horse breeding in the mid-1st millennium AD, and have also drawn prospects for future research on these topics.

Seasonal dynamics of gastroinstestinal helminths in naturally infected horses in Brazil

Helminthiasis in horse breeding stands out due to the damage caused by this infection, which is mainly controlled by anthelmintic drugs. Knowing the population dynamics of helminths in a given region is therefore essential, as environmental conditions have a major impact on the development of these parasites in pastures. The aim of this study was to assess the influence of seasonality on helminths. It was carried out between October and September of the years 2015/2016, 2018/2019 and 2021/2022. A total of 147 animals were used, 64 females and 83 males, all from the same herd. Fecal samples were collected directly from the rectal ampulla of each animal every 28 days for 12 months of each cycle for coproparasitological analysis. Average air temperature, average relative humidity and rainfall were measured daily. The weather records were collected by the Agroclimatological Station in Castilho, SP (21o 05' 12.4" S; 51o 35' 17.2" W), located six kilometers from the experiment site. In the three study cycles, the EPG and rainfall averages showed significant differences between the times of year. In general, the month with the highest EPG in the different cycles was February, with 1626 in 2015/2016, 926.7 in 2018/2019 and 1885 in 2021/2022, and the month with the lowest average EPG was July, with 642 in 2015/2016, 610.5 in 2018/2019 and 804 in 2021/2022. Regarding climatic conditions, rainfall was more concentrated in two seasons, spring and summer, meaning that summer was the season with the highest rainfall in the three cycles evaluated. Autumn, followed by winter were the seasons with the lowest rainfall during the cycles studied. It can be concluded that climatic conditions have a direct influence on the population dynamics of helminths, and that during the drier and colder seasons, horses were less affected, so the suggestion for a possible strategic program would be to concentrate the administration of anthelmintics in spring and summer.

Serum 25(OH) Vitamin D Concentrations in Horses: Effects of Age, Gender, Breed, Skin Colour and Season.

The optimal amount of vitamin D required for the proper functioning of the immune system differs from the amount necessary for bone homeostasis. Furthermore, vitamin D metabolism varies among horses. Nevertheless, there is a dearth of information regarding reference values for vitamin D in horses, particularly in the Turkmen breed. The primary objectives of this study were to determine the concentrations of 25-hydroxyvitamin D (25(OH)Vit D) in Turkmen, Thoroughbred and mixed Turkmen×Thoroughbred horses and to explore the effects of various factors on it and its relationship with serum biochemical variables and signalment data. For the measurement of 25(OH)Vit D, 90 healthy horses (min age: 6months; max age: 10years) that were stable in the north of Iran (37°17'N, 55°18'E) were selected for clinical examination and complete blood biochemistry analysis. The horses were categorised into different groups based on sex, season (spring, n=45; autumn, n=45), breed (Turkmen, Thoroughbred and mixed Turkmen×Thoroughbred), age (<2years, 2-8years and >8years) and skin colour. Sampling was performed only once from each horse. In this study, the median serum concentration of 25(OH)Vit D in the sampled horses was 17.42ng/mL (IQR: 9.82-30.85). The serum 25(OH)Vit D concentration was significantly lower in autumn (median: 15.83ng/mL and IQR: 8.67-54.68) than in spring (median: 18.02ng/mL and IQR: 13.77-27.54) and was also lower in Turkmen horses (median: 15.83ng/mL and IQR: 11.63-23.12) than in mixed breed horses (median: 17.72ng/mL and IQR: 8.94-51.67) (p≤0.05). According to the results of the present study, the season had a significant effect on the serum 25(OH)Vit D concentration, and this difference was also observed between Turkmen horses and mixed-bred horses (p≤0.05). It is unclear whether the time of sun exposure or vitamin D content of diet causes the seasonal difference of 25(OH)Vit D concentration.

Genetic diversity and signatures of selection in Anglo-Arabian racehorses based on medium-density genotype data

The Anglo-Arabian horse breed (AA) is the result of crossing between Thoroughbred and Arabian horses renowned for versatility in show-jumping and racing. Southwest France and Sardinia in Italy are considered the historical nucleus of European AA breeding. Since little is known on genetic variability in the AA breed, especially those bred in the Sardinia region, this study investigates: i) inbreeding levels via pedigree and SNP genotyping; ii) runs of homozygosity (ROH) and selection signatures; iii) effective population size; and iv) distinctiveness of AA compared to Arabian and Thoroughbred horses. The ROH revealed an excessive amount of homozygosity, with a high kurtosis value observed in several chromosomes and an average inbreeding based on ROH of 21.1%. This latter value is higher compared to what was found based on pedigree data, highlighting the importance of complete pedigree records when estimating inbreeding based on genealogical data. The genomic inbreeding in AA horses was higher compared to other Italian horse breeds but lower than what was found in pure Thoroughbred and Arabian horses. This result suggests that the selection process for AA horses, may have prioritised racing ability over breed preservation which is the main goal in most local Italian breeds. The reduction in effective population size found in the latest 20 generations corroborates the potential presence of genetic diversity reduction due to selection in the AA breed. Remarkably, a large ROH island was identified on ECA17, which overlapped with two QTLs associated with racing performance.

Genomic-Inbreeding Landscape and Selection Signatures in the Polo Argentino Horse Breed.

Analyzing genetic variability and inbreeding trends is essential for effective breed management in animal populations. To this, the characterization of runs of homozygosity (ROH) provides a good genomic approach to study the phenomena. The Polo Argentino (PA) breed, globally recognized as the best adapted to playing polo, is known for its strong influence of Thoroughbreds, intense selective breeding, and extensive use of reproductive biotechnologies. This study investigates the PA's genomic variability, by characterizing the ROH landscape and identifying ROH islands (ROHi) as potential genomic footprints for the breed. PA horses (n = 506) were genotyped using EquineGGP™ array v5 (70 k). We calculated the inbreeding coefficient based on ROH (FROH-ancestral and recent) using a chromosomal approach. Finally, we identified genomic regions with increased ROH frequency (ROHi) and their associated genes. An average of 79.5 ROH per horse was detected, with a mean length of 4.6 Mb. The average FROH was 0.151, but most of them (54%) corresponded to ancestral inbreeding (ROH < 5.5 Mb). However, 4 ROHi were identified in ECA 1, 3, 7 and 17, containing 67 genes, some of which were related to behavior, neurodevelopment, and metabolic functions. This genomic analysis determined, for the first time, the length and location of homozygosity segments in the PA breed and identified ROHi associated with potential genomic regions and genes for positive selection in the breed.

A Genetic Make Up of Italian Lipizzan Horse Through Uniparental Markers to Preserve Historical Pedigrees.

Lipizzan is a famous horse breed dating back to 1580 when the original stud of Lipica was established by the Hasburg Archduke Charles II. Currently, the Italian State Stud of Lipizzan Horses (ASCAL) is a conservation nucleus managed through strict mating rules where mitochondrial DNA sequences are used to verify the correct assignment of mares to a historical pedigree maternal lineage. Here, we analyzed the D-loop sequences of Lipizzan horses from the ASCAL in Monterotondo (Rome, Italy) in order to confirm their pedigree assignment to known female founder families. The concurrent investigation of the paternal counterpart based on variation in the male-specific region of the Y chromosome (MSY) showed a prevalence of HT02 (80%), typical of the Neapolitan/Oriental wave. The mtDNA polymorphisms identified shaped nine haplotypes that were unequivocally assigned to each of nine classical mare families of the stud (Africa, Almerina, Argentina, Deflorata, Djebrin, Fistula, Ivanka, Sardinia, Spadiglia), while the Europa and Theodorosta families shared a tenth haplotype. New polymorphisms were identified in a not previously studied region (np 16100-16350). The mtDNA phylogenetic analysis revealed that the Lipizzans of the Monterotondo stud belong to six haplogroups (B, C, G, L, M, Q), out of the 18 recorded for the equine species. This work enabled us to identify and preserve ten haplotypes from the historical maternal lines in a small stud kept in genetic segregation for over 100 years.

INFLUENCE OF SCIENTISTS-HIPOLOGISTS OF THE INSTITUTE OF LIVESTOCK OF NAAS ON THE HORSE BREEDING OF UKRAINE: A REVIEW (to the 95th anniversary of the Livestock farming institute of NAAS and the 90th anniversary of the Department of horse breeding)

The article is devoted to the review of the formation and activities of the scientific structural unit on horse breeding of the Livestock farming institute of the NAAS, as a scientific center on horse breeding, which carries out scientific support of the industry, starting from 1944 and until now. In particular, the scientific influence of the employees of the scientific unit on horse breeding in Ukraine is analyzed. The personalities of scientists who worked in the department (laboratory) of horse breeding of the institute at different periods, their personal contribution to the horse breeding industry are considered. The achievements of the scientists-hipologists of the institute in breeding and technological research, the creation of new breeds, types, lines of horses, the improvement of the horse feeding system, elements of horse training, the study of the features of local horse populations in different regions of Ukraine are highlighted. The directions of scientific work, the created breeds, types and lines of horses, breeding, technological developments, research on genetics, feeding, biotechnology, economics in horse breeding are considered. In the article, the authors partially used archival research by Victoria Vyacheslavivna Kunets, in particular, information from her historical and bibliographic publication “Scientific achievements of scientists in the development of domestic horse breeding and horse breeding”, for which they express their sincere gratitude to her.

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.

The Prevalence of Gastric Ulcer Syndrome in 395 Horses in Jiangyin City, China, Jiangsu Province.

The aim of this study was to determine the prevalence and association of EGUS in horses of different ages, breeds and occupations. Gastroscopies were performed on 395 horses, and gastric ulcers were graded on a scoring system from 0 to 4. The relationship between age, breed, and work, along with the prevalence of gastric ulcers and their influences, were evaluated. The prevalence rate of ulcers in this herd was 78%. Older horses were prone to ulcers in both the glandular and squamous mucosal areas. Across the different jobs surveyed, 60% of the horses had a score of 2 or above. For the horses participating in more intense jobs (group performances, pulling carts, etc.), the number of horses with an ulcer score of 2 or above exceeded 50% of the total number of horses in this job. The prevalence of gastric ulcers was high, and these ulcers were severe in the horses belonging to the examined club, with no association between age or breed and the prevalence of ulcers; however, there was a difference in the location of the ulcers between breeds, as well as differences in the incidence and severity of ulcers depending on work activity. This study provides data reference values for the control and prevention of gastric ulcers in horses in this horse farm.

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.

130 Comparative analysis of fertilization success between intracytoplasmic sperm injection and conventional in vitro fertilization in equine reproduction

130 Comparative analysis of fertilization success between intracytoplasmic sperm injection and conventional in vitro fertilization in equine reproduction

Study of Variation of ACOX1 Gene Among Different Horse Breeds Maintained in Iran.

The ACOX1 gene is vital for fatty acid metabolism and is linked to environmental stress and physical exertion adaptation. The p.Asp237Ser variant (rs782885985) in ACOX1 is associated with increased enzyme activity and reactive oxygen species (ROS) levels. This study examined the ACOX1 polymorphism across six horse breeds in Iran: Arabian, Thoroughbred, KWPN, Caspian, Kurdish, and Turkmen. The goal was to identify differences in ACOX1 genotype distribution, potentially serving as genetic markers under selection pressure related to breed-specific traits. In a sample of 324 horses, genomic DNA was analyzed using PCR-RFLP, revealing three genotypes (TT, TG, GG). The GG genotype was most common in Kurdish and Arabian horses (86% and 70%, respectively), while the TT genotype was prevalent in Turkmen (24%) and Thoroughbred horses (23%). The T allele's frequency in Thoroughbred and Turkmen horses suggests that ACOX1 may be under selection pressure for phenotypic traits. Differences in genotype distribution were confirmed among breeds, with no sex-based association. The study concludes that ACOX1 is a potential genetic marker for horse performance and adaptability, emphasizing the importance of genetic diversity in breeding programs.

Intrauterine Therapy with Platelet-Rich Plasma for Persistent Breeding-Induced Endometritis in Mares: A Review

This review aims to emphasize the scientific focus on platelet therapies by presenting the results already obtained in mares susceptible to Persistent Breeding-Induced Endometritis (PBIE), as well as highlighting opportunities for further improvement. The recent publication demonstrating the absence of bacterial growth in susceptible mares treated with PRP underscores the potential of regenerative therapies to control infections without promoting the emergence of multidrug-resistant bacteria. Alternative therapies have gained prominence in the current public health context, with the World Health Organization listing antimicrobial resistance among the ten most significant global threats. Endometritis is the leading cause of subfertility in mares, and empirical antibiotic therapies are commonly used in the field due to market pressures related to the high financial value of embryos, along with logistical challenges in obtaining laboratory-dependent diagnostic results. Platelet-Rich Plasma (PRP) is an alternative therapy derived from whole blood plasma with a high concentration of platelets. Its anti-inflammatory, regenerative, and antimicrobial properties are particularly tested when traditional therapies fail to achieve the desired effect. In recent years, research on the use of PRP in equine reproduction has primarily focused on endometritis, with a particular emphasis on persistent breeding-induced endometritis (PBIE). However, there is a growing interest in other platelet derivatives, such as lyophilized platelet-rich plasma and platelet lysate, which offer practical field applications.

Distribution of Bacterial Agents and Diagnosed Diseases in Samples Sent to the Jockey Club of Türkiye Istanbul Equine Hospital Laboratory: A Retrospective Study (2015-2019)

The categorization of diseases identified in Turkish race and breeding horses, as well as the bacterial agents derived from these equines, have not been thoroughly investigated. This study aimed to examine the bacterial agents in samples taken from sick horses brought to the covering stations and animal hospitals operating under the Jockey Club of Türkiye (TJK) between January 1, 2015, and December 31, 2019, and the retrospective distribution of diseases in the horses from which these samples were taken. It was determined that the most frequently sent sample to the TJK Istanbul Equine Hospital Laboratory was tracheal lavage fluid (47.3%) and that the samples were mostly sent in the spring (33.8%) and autumn (30.8%) seasons. It was determined that the most common respiratory system infections (49.37%), followed by genital system infections (29.11%) and gastrointestinal system infections (18.57%) were seen in the horses from which the samples were taken. In all samples sent, the most isolated pathogen was Escherichia coli (15.6%). In respiratory system infections, the most identified pathogens were Streptococcus equi subsp. zooepidemicus (14.53%), followed by Streptococcus dysgalactiae subsp. equisimilis (11.11%) and Streptococcus equi subsp. equi (10.26%). In horses diagnosed with gastrointestinal system diseases, the most isolated pathogens were Escherichia coli (37.21%), followed by Corynebacterium jeikeium (18.60%). As a result, it is expected that the findings obtained from this study will contribute to taking specific measures against diseases or bacterial agents with high prevalence in enterprises operating within the TJK and minimizing losses due to horse diseases.

Sleeping and Eating Behavior Recognition of Horses Based on an Improved SlowFast Network.

The sleeping and eating behaviors of horses are important indicators of their health. With the development of the modern equine industry, timely monitoring and analysis of these behaviors can provide valuable data for assessing the physiological state of horses. To recognize horse behaviors in stalls, this study builds on the SlowFast algorithm, introducing a novel loss function to address data imbalance and integrating an SE attention module in the SlowFast algorithm's slow pathway to enhance behavior recognition accuracy. Additionally, YOLOX is employed to replace the original target detection algorithm in the SlowFast network, reducing recognition time during the video analysis phase and improving detection efficiency. The improved SlowFast algorithm achieves automatic recognition of horse behaviors in stalls. The accuracy in identifying three postures-standing, sternal recumbency, and lateral recumbency-is 92.73%, 91.87%, and 92.58%, respectively. It also shows high accuracy in recognizing two behaviors-sleeping and eating-achieving 93.56% and 98.77%. The model's best overall accuracy reaches 93.90%. Experiments show that the horse behavior recognition method based on the improved SlowFast algorithm proposed in this study is capable of accurately identifying horse behaviors in video data sequences, achieving recognition of multiple horses' sleeping and eating behaviors. Additionally, this research provides data support for livestock managers in evaluating horse health conditions, contributing to advancements in modern intelligent horse breeding practices.

Unraveling the maternal heritage: identifying the complex origins of indigenous Indian horse and pony breeds through mitochondrial genome analysis.

This study explored the maternal genetic diversity of six indigenous Indian horse and pony breeds (Bhutia, Kathiawari, Manipuri, Marwari, Spiti, and Zanskari) using comprehensive mitochondrial genome (mitogenome) analysis. Blood samples from 53 horses across diverse agro-climatic zones of India were analyzed, revealing 36 distinct haplotypes, with a haplotype diversity of 0.889 and nucleotide diversity of 0.00347. These indices suggest significant maternal genetic diversity in Indian equines. A median-joining (MJ) network, based on the hypervariable region of the D-loop along with sequences of Indian equids retrieved from the NCBI, identified 55 haplotypes, including shared haplotypes across 2-5 breeds. Hierarchical AMOVA analysis revealed that 95.20% of genetic variation was within populations, while only 4.80% was among different groups, indicating minimal genetic structuring based on geographic distribution. Phylogenetic analysis of these mitogenomes, alongside global sequences, revealed significant genetic variability without clear geographic clustering, highlighting extensive gene flow and interbreeding across regions. Median-Joining network based on D-loop sequence revealed that Indian horses conform to seven of the 18 globally recognized haplogroups (A, B, G, J, L, M, and P), with haplogroup A being the most frequent. This research contributes to the broader understanding of equine genetic diversity, aligning with global patterns of extensive maternal haplotype diversity, and underscores the intricate genetic backgrounds resulting from historical breeding practices.

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.