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Nine different species of Equus caballus papillomavirus (EcPV) and three bovine papillomaviruses (BPVs) have been reported to infect horses. However, there are few descriptions of such infections in China. In our pioneer study on Chinese horses, we identified EcPV-2 in the nasal swabs (4/230, 1.7%) of Yili horses, and the semen (3/18, 16.7%) of thoroughbred horses. This indicated that EcPV is indeed hosted by horses in China, and that EcPV-2 might be transmitted though breeding. Further detection of EcPVs in the lung tissues of aborted fetuses of Yili horses, which were originally negative for equid herpes viruses, demonstrated EcPV-2 positivity in 19 of 50 samples, thereby indicating that EcPV-2 may be a new pathogen responsible for causing abortion. Thereafter, sequence analyses of the L1 genes of 26 EcPV-2 in China were performed, indicating that EcPV-2, which primarily infects horses in China, shared 98.3–99.9% nt identity with the published sequences for EcPV-2. These observations indicated that EcPV-2 identified in the current study were highly similar variants of the previously identified strains of EcPV-2. Phylogenetic analysis based on L1 gene sequences from GenBank showed that the EcPV-2 found in Chinese horses was closely related to and clustered together with an already known EcPV-2a lineage. Our study provides the first evidence related to EcPV-2 infection in Chinese horses, which can serve as a causative agent for Yili horse abortions, and may thus lay the foundation for a systematic and detailed epidemiological study of this infection in Chinese horses.

Accurate population estimates provide the foundation for managing feral horses (Equus caballus ferus) across the western United States. Certain feral horse populations are protected by the Wild and Free-Roaming Horses and Burros Act of 1971 and managed by the Bureau of Land Management (BLM) or the United States Forest Service on designated herd management areas (HMAs) or wild horse territories, respectively. Horses are managed to achieve an appropriate management level (AML), which represents the number of horses determined by BLM to contribute to a thriving natural ecological balance and avoid deterioration of the range. To achieve AML for each HMA, BLM resource managers need accurate and precise population estimates. We tested the use of non-invasive fecal samples in a genetic capture-recapture framework to estimate population size in a closed horse population at the Little Book Cliffs HMA, Colorado, USA, with a known size of 153 individuals. We collected 1,957 samples over 3 independent sampling periods in 2014 and amplified them at 8 microsatellite loci. We applied mark-recapture models to determine population size using 954 samples that amplified at all 8 loci. We subsampled and reanalyzed our dataset to simulate different data collection protocols and evaluated effects on accuracy and precision of estimates using N-mixture modeling, full likelihood closed-capture modeling, and capwire single-occasion modeling that used data from all 3 sampling periods. Our model results were accurate and precise for analyses that used data from all 3 occasions; however, capwire single-occasion modeling was not accurate when we analyzed each sampling period separately. For all subsampling analysis scenarios, reducing sample size decreased precision, whether by reducing number of field staff, field days, or geographic areas surveyed on each period. Reducing spatial coverage of the survey area did not result in accurate population estimates and only marginally lowered the number of samples that would need to be collected to maintain accuracy. Because laboratory analysis contributes the greatest expense for this method ($80 U.S./sample), reducing fecal sample size is advantageous. Our results demonstrate that non-invasive sampling combined with good survey design and careful genetic and capture-recapture analyses can provide an alternative method to estimate the number of feral horses in a closed population. This method may be especially appropriate in situations where aerial inventories are not practical or accurate because of low sighting conditions. But the higher costs associated with laboratory sample analyses may reduce the method–s feasibility compared to helicopter surveys.

This paper presents historical and evolutionary insights into the “tarpan” group of small horses by examining molar tooth enamel ultrastructure. Mathematical methodologies were applied to enhance the analysis. Tooth enamel from species such as Equus gmelini (tarpan), E. latipes, and E. hydruntinus from Pleistocene Ukrainian localities, E. przewalskii from the Chornobyl Exclusion Zone in Ukraine, and E. caballus form sylvaticus (Polish konik) from Roztocze National Park, Poland, underwent scanning microscope examination. Measurements of enamel structures, including prisms (PE) and interprismatic matrix (IPM), were conducted, with the K-index used as their ratio, categorized by enamel type (I, II, III). The findings confirmed that the crystal structures of enamel in these horse groups vary based on genus evolution, diet, and environmental conditions, shaping the enamel’s morphological features. Through analysis, clusters were identified, allowing for potential reconstructions of relationships among study groups. The results revealed distinct differences between species, enabling their classification within an established phenogram. Two primary clusters emerged: one consisting of extinct small horse forms from diverse localities and another grouping modern forms. Notably, the Late Pleistocene European species E. latipes showed close affinities to the latter cluster.

External hoof characteristics, balance, and conformation have been extensively studied in horses; however, mules remain understudied in these aspects. This study evaluated the size, shape, and symmetry of untrimmed and unshod forelimb hooves, compared the symmetry between forelimb hooves and stratified external forelimb hoof measurements based on the body condition score of mules raised in the foothill plains of northern Thailand. The forelimb hooves of 38 mules were photographed and 33 parameters, including angular and linear measurements, were analyzed. A multivariate analysis was used to explore the influence of sex, age, and body condition scores (BCS) on angular, linear, and area parameters. Additionally, one-way ANOVA followed by Tukey’s test was used to compare these parameters across different BCS groups. Despite the absence of shoeing and trimming, these mules exhibited optimal left–right forelimb hoof symmetry, with no significant (p < 0.05) differences in: outer wall length and inner wall length (OWL–IWL: Left 0.11 ± 0.66 cm; Right −0.12 ± 0.43 cm); sole length and sole width (SLS–SW: Left 1.65 ± 0.76 cm; Right 1.46 ± 0.89 cm); dorsal hoof wall length and heel length (DHWL–HL: Left 4.00 ± 0.80 cm; Right 3.81 ± 0.72 cm); and frog length and frog width (FL–FW: Left 3.88 ± 1.13 cm; Right 3.82 ± 0.18 cm). However, significant (p < 0.05) differences were observed within each body condition score group for forelimb hoof measurements for DHWL, IWL, heel separation (HS), heel bulb distance (HBD), SW, FW, and FL, while sex and age had no significant differences across the study variables. These findings provide valuable insights into mule welfare and management, contributing to understanding of the interplay between overall health and hoof conformation in the study area.

An extensive analysis of the relationship between age, sex, and different types of management strategies relative to the gastrointestinal parasite community of Polish primitive horses was performed on 124 horses maintained in nine farms from four regions of Poland. The horses (96 females and 28 males) were housed in three types of management strategies: stabled (ST), free-ranging (FR) and semi-free (SF). These horses also were divided into three age groups: <3 years, 3 – 10 years and >10 years old. The gastrointestinal parasites were collected following deworming of all horses with anthelmintics containing the macrocyclic lactones and praziquantel. Totally, 66,192 parasite specimens were collected and identified. The analysis of dependence of horse infection with intestinal nematodes using sex, age and management strategies demonstrated that females had significantly heavier infections of strongylids. Young horses (<3 years old) had higher infections of and . Free ranging horses were more infected with strongylids, and . Thirty-five nematode species, one cestode and one species of the botfly larvae of were found. Diagnostic deworming examination revealed presence of in 27.4 %, in 38.7 %, in 16.9 %, in 42.7 % and in 46.8% in the Polish primitive horses examined. presence was confirmed only by fecal samples examination; threadworms were not observed in these horses after deworming. In the strongylid community, 31 species (6 of subfamily Strongylinae and 25 of Cyathostominae) were found. Significant differences in prevalence of separate strongylid species, or their proportions in the communities were not observed between females and males, or between age groups (p > 0.05). The highest species diversity (n=30 or 31) was observed in the FR horses, the lowest (n=15) – in ST horses. The FR horses had higher prevalence and proportion of large strongyles in the community, in comparison to SF or ST horses (p < 0.05).

For many ecosystems, feral horses are increasingly becoming an important if not dominant component of ungulate biomass and hence influence on community dynamics. Yet we still know little of how horses contribute to key ecological interactions including predator-prey and indirect competitive relationships at a community level. Notably, feral species like horses can exhibit life-history traits that differ from that of native (mainly artiodactyl) herbivore competitors. Artificial selection for traits like increased, early, or extended reproduction that have yet to be reversed by natural selection, coupled with naturally selected differences in anatomy and behavior, in addition to unique management objectives for horses compared to other species, means that the dynamics of feral horse populations are not likely to align with what might be expected of other large herbivores. Unexpected population dynamics and inherent biological asymmetries between native ungulates and feral horses may therefore influence the former via direct competition for shared resources and through enemy-mediated interactions like apparent competition. In several localities feral horses now co-exist with multiple native prey species, some of which are in decline or are species at risk. Compounding risks to native species from direct or indirect competitive exclusion by horses is the unique nature and socio-political context of feral horse management, which tends towards allowing horse populations to be limited largely by natural, density-dependent factors. We summarize the inherent asymmetries between feral horse biology and that of other ungulate prey species with consequences for conservation, focusing on predator-prey and emerging indirect interactions in multi-prey systems, and highlight future directions to address key knowledge gaps in our understanding of how feral horses may now be contributing to the (re)structuring of food webs. Observations of patterns of rapid growth and decline, and associated skews in sex ratios of feral horse populations, indicate a heightened potential for indirect interactions among large ungulate prey species, where there is a prevalence of feral horses as preferred prey, particularly where native prey are declining. In places like western North America, we expect predator-prey interactions involving feral horses to become an increasingly important factor in the conservation of wildlife. This applies not only to economically or culturally important game species but also at-risk species, both predators (e.g., wolves [Canis lupus], grizzly bears [Ursus arctos]) and prey (e.g., woodland caribou [Rangifer tarandus caribou]), necessitating an ecological understanding of the role of horses in natural environments that goes beyond that of population control.

There is little information about serum biochemistry in hinnies, animals that are usually confused with mules, so this is why specific diagnosis and treatment for these animals are difficult to obtain. Due to this fact, this study had the aim of offering elements to understand and determine references in serum biochemistry parameters specific for hinnies. To achieve this objective, biochemistry parameters from blood samples collected from 33 healthy animals (15 male hinnies with age between 7 and 84 months, and 18 female hinnies with age between 17 days and 84 months), from different farms in Brazil, were evaluated to verify the influence of age and sex of animals on these parameters. The analyzed elements were total protein, albumin, globulin, albumin:globulin (A:G) ratio, cholesterol, triglycerides, uric acid, creatinine, urea, calcium, phosphorus, calcium-phosphorus ratio (Ca:P), magnesium, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), and creatine kinase (CK). Animal’s ages had an influence on biochemistry parameters, as the younger animals (≤ 30 months) presented higher levels of phosphorus and higher albumin:globulin ratio. Males and females presented similar serum biochemistry profiles. The results of this study offer elements to determine the serum biochemistry profile of hinnies and have enormous importance for veterinary clinic since this is one of the first researches in this area.

Management of wild horse (Equus ferus caballus) populations on western U.S. rangelands has been a challenge since horses were given legal protection through the passage of the Wild Free-Roaming Horses and Burros Act (WFRHba) in 1971. Horses have no effective predators, and unmanaged populations can double in 4-5 years and triple in 6-8 years. In order to meet the multiple-use paradigm for managing public rangelands, the Bureau of Land Management (BLM) has limited horse population growth through the periodic capture and removal of animals. While the WFRHBA mandates disposal of captured horses through placement into private ownership and prompt destruction of any excess animals, administrative restrictions have prohibited the destruction of healthy horses for nearly the entire history of the management program. This has led to an ever-increasing number of unwanted horses maintained in captivity, which has required increasing Congressional appropriations. There are currently 44,000 horses in long-term captivity at an annual cost of approximately $50 million. Recently, Congress has denied requests from the BLM for further funding increases to support continued growth in the number of horses in long-term maintenance, obligating the BLM to dramatically curtail population management. Horse numbers on public rangelands are now rapidly increasing, and if left minimally managed will exceed the capacity of rangeland resources, resulting in serious degradation of these public lands for all other uses and eventually will result in large numbers of horses dying of starvation and dehydration. Horse advocates suggest this management crisis can be solved with the aggressive use of contraceptive technologies. Limitations in efficacy and the logistics of administering contraceptives indicate that contraceptives can only slow population growth rates, but alone cannot decrease numbers. The BLM and other stakeholders are pressing for authorization to destroy excess horses but are facing public and Congressional opposition, with the potential that the status quo continues. A sustainable wild horse and burro (E. asinus; WhB) management program could be achieved by a combination of reducing the on-range population and treating adequate numbers of horses remaining on rangelands with contraceptives to reduce subsequent population growth rates. Under this scenario, the freeroaming horse population would produce a modest annual increment of horses, which could be removed and readily placed into private ownership. It has taken nearly half a century for the wild horse problem to reach this critical point, and any transition to a sustainable program will take time and additional resources. The fundamental challenge to developing a sustainable program will be solving the problem of the fate of excess horses. The policy decisions confronting us are historic, challenging, and controversial with a real danger of not finding the resolve to chart a new course for the WHB Program. If we fail and continue with the current policies, then horses, native wildlife, all stakeholders, and our public rangelands will pay a heavy price.

Although previous studies of horses have investigated their facial expressions in specific contexts, e.g. pain, until now there has been no methodology available that documents all the possible facial movements of the horse and provides a way to record all potential facial configurations. This is essential for an objective description of horse facial expressions across a range of contexts that reflect different emotional states. Facial Action Coding Systems (FACS) provide a systematic methodology of identifying and coding facial expressions on the basis of underlying facial musculature and muscle movement. FACS are anatomically based and document all possible facial movements rather than a configuration of movements associated with a particular situation. Consequently, FACS can be applied as a tool for a wide range of research questions. We developed FACS for the domestic horse (Equus caballus) through anatomical investigation of the underlying musculature and subsequent analysis of naturally occurring behaviour captured on high quality video. Discrete facial movements were identified and described in terms of the underlying muscle contractions, in correspondence with previous FACS systems. The reliability of others to be able to learn this system (EquiFACS) and consistently code behavioural sequences was high--and this included people with no previous experience of horses. A wide range of facial movements were identified, including many that are also seen in primates and other domestic animals (dogs and cats). EquiFACS provides a method that can now be used to document the facial movements associated with different social contexts and thus to address questions relevant to understanding social cognition and comparative psychology, as well as informing current veterinary and animal welfare practices.

Archaeological and genetic evidence concerning the time and mode of wild horse (Equus ferus) domestication is still debated. High levels of genetic diversity in horse mtDNA have been detected when analyzing the control region; recurrent mutations, however, tend to blur the structure of the phylogenetic tree. Here, we brought the horse mtDNA phylogeny to the highest level of molecular resolution by analyzing 83 mitochondrial genomes from modern horses across Asia, Europe, the Middle East, and the Americas. Our data reveal 18 major haplogroups (A–R) with radiation times that are mostly confined to the Neolithic and later periods and place the root of the phylogeny corresponding to the Ancestral Mare Mitogenome at ∼130–160 thousand years ago. All haplogroups were detected in modern horses from Asia, but F was only found in E. przewalskii—the only remaining wild horse. Therefore, a wide range of matrilineal lineages from the extinct E. ferus underwent domestication in the Eurasian steppes during the Eneolithic period and were transmitted to modern E. caballus breeds. Importantly, now that the major horse haplogroups have been defined, each with diagnostic mutational motifs (in both the coding and control regions), these haplotypes could be easily used to (i) classify well-preserved ancient remains, (ii) (re)assess the haplogroup variation of modern breeds, including Thoroughbreds, and (iii) evaluate the possible role of mtDNA backgrounds in racehorse performance.