Horse Research Articles

Artificial intelligence and classical methods in animal genetics and breeding

The article analyses basic methods of population genetics and animal breeding, as well as mathematical methods of machine learning used in animal breeding. The training of cat boost library models was carried out on the example of two domesticated species – domestic horse (Equus caballus) and reindeer (Rangifer tarandus). Data from microsatellite panels of 16 and 17 loci, respectively, were used to train the model using data on domesticated and wild reindeer, European and Russian horse breeds. The standard indicators: accuracy, precision, recall and f1 were calculated to determine the success of the model. Confusion matrices were constructed. New possibilities of identification of animal breed affiliation were shown.

Bat-associated ticks as a potential link for vector-borne pathogen transmission between bats and other animals.

Potentially zoonotic pathogens have been previously detected in bat-associated ticks, but their role in disease transmission and their frequency of feeding on non-bat hosts is poorly known. We used molecular blood meal analysis to reveal feeding patterns of the bat-associated tick species Ixodes ariadnae, I. simplex, and I. vespertilionis collected from cave and mine walls in Central and Southeastern Europe. Vertebrate DNA, predominantly from bats, was detected in 43.5% of the samples (70 of 161 ticks) but in these ticks we also detected the DNA of non-chiropteran hosts, such as dog, Canis lupus familiaris, wild boar, Sus scrofa, and horse, Equus caballus, suggesting that bat-associated ticks may exhibit a much broader host range than previously thought, including domestic and wild mammals. Furthermore, we detected the zoonotic bacteria Neoehrlichia mikurensis in bat ticks for the first time, and other bacteria, such as Bartonella and Wolbachia. In the light of these findings, the role of bat ticks as disease vectors should be urgently re-evaluated in more diverse host systems, as they may contribute to pathogen transmission between bats and non-chiropteran hosts.

Exploring horses' (Equus caballus) gaze and asymmetric ear position in relation to human attentional cues.

Studies have shown that horses are sensitive to human attentional cues. Also, there is some evidence that they might be able to infer the knowledge state of a human and communicate intentionally with us. However, this ability is not fully characterized and certain behaviors, like gaze, asymmetric ears position or vocalizations, which could work as attention-getting behaviors, have been scarcely studied in this context. The aim of the present study was to assess whether horses' gaze toward a person, asymmetric ears position and vocalizations are subject to audience effects and adjust to human attentional cues, which would suggest a communicative function. For this purpose, we adapted a protocol used with domestic dogs [Kaminski et al. 2017] and observed horses' spontaneous behavior (gaze, asymmetric ears position and vocalizations) in the presence of a human holding and not holding food in an attentive position (facing the horse with open eyes) and in a non-attentive position (with her back turned towards the horse). We found significant evidence of horses being sensitive to human attentional cues (reflected in the horses' gaze duration and asymmetric position of the ears), but not of intentional communication towards humans.

Horse Meat Microbiota: Determination of Biofilm Formation and Antibiotic Resistance of Isolated Staphylococcus Spp.

Domestic horses could be bred for leisure activities and meat production, as is already the case in many countries. Horse meat is consumed in various countries, including Kazakhstan and Kyrgyzstan, and with the increase in this consumption, horses are registered as livestock by the Food and Agricultural Organization. In this study, horse meat microbiota of horse samples (n = 56; 32 samples from Kazakhstan and 24 samples from Kyrgyzstan) from two countries, Kazakhstan (n = 3) and Kyrgyzstan (n = 1), were investigated for the first time by next-generation sequencing and metabarcoding analysis. The results demonstrated that Firmicutes, Proteobacteria, and Actinobacteria were the dominant bacterial phyla in all samples. In addition, three (5.4%) Staphylococcus strains were isolated from the Uzynagash region, Kazakhstan. Staphylococcus strains were identified as Staphylococcus warneri, S. epidermidis, and S. pasteuri by partial 16S rRNA DNA gene Sanger sequencing. All three Staphylococcus isolates were nonbiofilm formers; only the S. pasteuri was detected as multidrug-resistant (resistant to penicillin, cefoxitin, and oxacillin). In addition, S. pasteuri was found to carry mecA, mecC, and tetK genes. This is the first study to detect potentially pathogenic Staphylococcus spp. in horse meat samples originating from Kazakhstan. In conclusion, it should be carefully considered that undercooked horse meat may pose a risk to consumers in terms of pathogens such as antibiotic-resistant Staphylococcus isolates.

A Comprehensive Analysis of the Genomic and Expressed Repertoire of the T-Cell Receptor Beta Chain in Equus caballus

In this paper, we report a comprehensive and consistent annotation of the locus encoding the β-chain of the equine T-cell receptor (TRB), as inferred from recent genome assembly using bioinformatics tools. The horse TRB locus spans approximately 1 Mb, making it the largest locus among the mammalian species studied to date, with a significantly higher number of genes related to extensive duplicative events. In the region, 136 TRBV (belonging to 29 subgroups), 2 TRBD, 13 TRBJ, and 2 TRBC genes, were identified. The general genomic organization resembles that of other mammals, with a V cluster of 135 TRBV genes located upstream of two in-tandem aligned TRBD-J-C clusters and an inverted TRBV gene at the 3′ end of the last TRBC gene. However, the horse b-chain repertoire would be affected by a high number of non-functional TRBV genes. Thus, we queried a transcriptomic dataset derived from splenic tissue of a healthy adult horse, using each TRBJ gene as a probe to analyze clonotypes encompassing the V(D)J junction. This analysis provided insights into the usage of the TRBV, TRBD, and TRBJ genes and the variability of the non-germline-encoded CDR3. Our results clearly demonstrated that the horse β-chain constitutes a complex level of variability, broadly like that described in other mammalian species.

Serological monitoring of Influenza A among wild and domestic ungulates in Ukraine

The article provides a brief historical background of equine influenza, the spread of this disease worldwide, and the current epizootic situation. The results of serological monitoring by ELISA of wild and domestic ungulates from different farms and regions of Ukraine for the presence of antibodies to influenza A viruses are presented. Blood serum samples from 372 domestic horses and 32 wild ungulates were tested. Samples from animals collected in 2023 and 2024 and archival blood serum samples from 2021 were used and tested according to the manufacturer’s instructions using ELISA test systems manufactured by IDEXX, INGEZIM, and IDVet. The data obtained indicate a fairly active circulation of influenza A viruses in populations of unvaccinated domestic horses. The circulation was established not only in recent years (2023–2024, seroprevalence from 10% to 100%), but was observed earlier, as evidenced by the detection of 60.9% of positive samples in samples collected in 2021. In addition, two out of three positive samples were found in wild horses from Kherson Region, which indicates the circulation of influenza A virus among wild animals and requires further investigation. The results correlate with the worsening of the epidemiological situation regarding influenza in animals in Europe. The subsequent phase of the research is serotyping, which involves determining the presence of antibodies to specific virus subtypes by hemagglutinin

Free‐roaming horses exceeding appropriate management levels affect multiple vital rates in greater sage‐grouse

AbstractSince the passage of the Wild Free‐Roaming Horses and Burros Act of 1971, federal agencies have been responsible for managing free‐roaming equids in the United States. Over the last 20 years, management has been hampered by direct opposition from advocacy groups, budget limitations, and a decline in the public's willingness to adopt free‐roaming horses (Equus caballus). As a result, free‐roaming equid numbers have increased to >3 times the targeted goal of 26,785 (horses and burros [E. asinus] combined), the cumulative sum of the appropriate management levels (AML) for all 177 designated herd management areas (HMA) managed by the Bureau of Land Management. This increase is one of the causes of greater sage‐grouse (Centrocercus urophasianus) population declines, owing to habitat alteration from free‐roaming equids exacerbated by ongoing drought. To evaluate potential demographic mechanisms influencing these declines, we compiled survival data from 4 studies in central Wyoming, USA, including 995 adult female (first‐year breeders or older) sage‐grouse during the breeding season, 1,075 nests, 372 broods, and 136 juveniles (i.e., overwinter survival for fledged young), from 2008–2022. During this period, we also obtained population information for free‐roaming horses from 9 HMAs used by individual grouse in our sample. Population estimates of free‐roaming horses for these HMAs ranged from 59% to 7 times of the maximum appropriate management level (AMLmax). Sage‐grouse monitored outside of HMAs represented control populations and, because we assumed they were not exposed to populations of free‐roaming horses, we set values of AMLmax to zero for all grouse located outside of HMAs. To evaluate whether free‐roaming horses were negatively affecting sage‐grouse, we modeled daily survival of breeding age females, nest, broods, and juveniles. There was strong or moderate evidence that overabundant free‐roaming horses negatively affected nest, brood, and juvenile survival. When horse abundance increased from AMLmax to 3 times AMLmax, survival was reduced 8.1%, 18.3%, 18.2%, and 18.2% for nests, early broods (≤20 days after hatch), late broods (>20 days to 35 days after hatch), and juveniles, respectively. These results indicate increasing free‐roaming horse numbers affected vital rates for important life stages of sage‐grouse, and that maintaining free‐roaming horse numbers below AMLmax would reduce negative effects to sage‐grouse populations.

The Use of Genomic Screening for the Detection of Chromosomal Abnormalities in the Domestic Horse: Five New Cases of 65,XXY Syndrome in the Pura Raza Español Breed.

Sex chromosomal abnormalities are a well-established cause of reproductive failure in domestic horses. Because of its difficult diagnosis, the Pura Raza Español breeding program established a routine screening for chromosomal abnormalities in all the horses prior to enrolling in the studbook. This genomic procedure combines an initial assessment based on the results from Short Tandem Repeat (STR) parentage testing followed by a Single-Nucleotide Polymorphism (SNP) based copy number aberration (CNA) confirmative analysis in positive cases. Using this methodology, we identified five new individuals carrying a 65,XXY chromosomal number aberration (CNA) among 27,330 foals enrolled over the past two reproductive seasons. The animals were initially flagged as CNA candidates due to abnormal results in STR testing. Subsequent analysis genotyping using an STR sex-linked dedicated panel and a medium-density SNP array in ECAX and ECAY confirmed the diagnosis as 65,XXY carriers. Four cases (upon sample availability) underwent further analysis using in situ fluorescent hybridization with ECAX and ECAY probes, showing identical results. Phenotypic analysis revealed abnormal gonad development in one of the cases, showing that the remaining four had a normal reproductive morphology. To our knowledge, this represents the largest number of horses exhibiting the equine form of Klinefelter syndrome (65,XXY) reported to date. Our study highlights the importance of genomic screening in the accurate detection of chromosomal abnormalities in horses.

Anatomy of the Right and Left Ventricular Subvalvular Apparatus of the Horse (Equus caballus).

Due to the growing interest among veterinarians and the increasing market demands, the development of equine cardiology is necessary. Currently, veterinary medicine for companion animals needs to catch up to human medicine-equine medicine included. A common condition in older horses is aortic valve regurgitation resulting from fibrosis, while its more severe form occurs in younger horses or develops due to a bacterial infection. Mitral valve regurgitation, especially dangerous due to the possibility of sudden death, has a better prognosis if the horse has valve prolapse. Tricuspid valve regurgitation usually does not pose a clinical problem, although its severe cases may lead to heart failure. Some pathologies can be treated surgically, which requires excellent knowledge of anatomy. The object of this study consisted of twenty domestic horse hearts. The focus was on the normal and comparative anatomy of the left and right subvalvular apparatus. The number of muscular bellies of the papillary muscles and the type of connection of the muscles were analysed. Moreover, the height of muscle originating from the ventricle wall was determined, the morphological regularity of the papillary muscle was assessed, and the chordae tendineae originating from the papillary muscles were examined. The conducted research allowed for comparing domestic horses with different species through other studies, the authors of which described this particular aspect. Interspecies similarities which may be correlated with the evolutionary relatedness, as well as differences that could reflect adaptation to different lifestyles, environmental conditions, or metabolic requirements of the animals, have been found. This study expands the knowledge of animals' normal and comparative anatomy, and contributes to the development of veterinary surgery, internal medicine, and biology.

An Upper Paleolithic horse mandible with an embedded lithic projectile: Insights into 16,500 cal BP hunting strategies through a unique case of bone injury from Cantabrian Spain

AbstractEmbedded artifacts in osteoarchaeological remains may be key to approaching hunting strategies and other behavioral‐related issues such as technological development. However, that kind of evidence is not common within the archaeological record and often not well‐characterized, especially for faunal remains from prehistoric sites. Here, we present and discuss a unique case of a horse (Equus caballus) mandible with an embedded lithic remains from the Upper Paleolithic (ca. 17,300–16,200 cal BP) from La Garma cave in Cantabria, Spain. Our macro‐ and microscopic faunal and lithic integrated analysis suggests that the case presented here is a potential perimortem hunting lesion, representing an uncommon hunting strategy during the Magdalenian period. Furthermore, this study, representing the first case of its kind in the Iberian Peninsula, emphasizes the importance of the taphonomic analysis of bone surfaces to approach the understanding of past human behaviors.

From Human Perception of Good Practices to Horse (Equus Caballus) Welfare: Example of Equine-Assisted Activities.

Equine-assisted intervention (EAI) studies deal with clients, whereas very few studies focused on the effects on animals. EAI equids are also submitted to management, which influences their welfare. Management and working conditions depend on human decisions and perception. We gathered information through a survey about facilities managers' strategies (n = 51) and obtained direct information on management and working practices and their consequences on equids' welfare through an observational study (n = eight facilities, 174 equids). Differences in managers' perceptions of good management practices were related to the facility's involvement in EAI, e.g., increased awareness of equids' needs (housing and feeding), especially when EAI was the main activity. A detailed observational study on eight additional facilities confirmed that. Facility management profiles were paralleled by equids' welfare profiles. Clear correlates were found between management decisions and welfare consequences. One major factor influencing welfare and human-equid interactions appeared to be working modalities, with more EAI facilities practicing groundwork and bitless work. Facilities where equids were the most involved in mixed activities had the most equids with compromised welfare. Given EAI clients' particularities, conventional working modalities are less adapted and at risk of increased discomfort for equids. Overall, survey and observational approaches converged but some discrepancies (choice of equid type) appeared between the reported and observed prevalence.

Anthelmintic treatments and strongylid community: alterations in the species composition and parasite community structure in domestic horses

Anthelmintic treatments and strongylid community: alterations in the species composition and parasite community structure in domestic horses

Craniometric values of the domestic horse (Equus caballus) in the context of mechanical stunning anatomy – preliminary studies

Abstract This study presents selected craniometric measurements compared to the thickness of the frontal bone of the domestic horse. The study was carried out on 10 domestic horse skulls from the collection of the Institute of Veterinary Medicine at Nicolaus Copernicus University in Torun. On the basis of the results obtained, correlation was carried out according to Pearson’s method, and a trend graph was created, showing the relationship of individual values to frontal bone thickness. The present research is a preliminary study, and further research, based on a larger study group, can help minimize their suffering. According to the study, the greatest positive correlation and relationship is shown by the length between the alveolar borders of the third incisor, while a negative correlation was found for the width of the cerebrocranium. In the future, it is possible to develop a formula to estimate the thickness of the frontal bone in horses.

PHARMACOKINETIC PROFILES OF ORAL PHENYLBUTAZONE, MELOXICAM, AND FIROCOXIB IN SOUTHERN BLACK RHINOCEROS (DICEROS BICORNIS MINOR).

The pharmacokinetic profile of selected NSAIDs in southern black rhinoceros (Diceros bicornis minor) were studied. Phenylbutazone (PBZ), meloxicam (MEL), and firocoxib (FIR) were administered orally to five captive, black rhinoceros, and blood was collected at predetermined time points for NSAID quantification and noncompartmental pharmacokinetic (PK) analysis. Phenylbutazone 4.0 mg/kg PO q12h for three doses, MEL 0.3 mg/kg PO q24h administered twice, and a single oral dose of FIR 0.1 mg/kg, were tested with a minimum washout time of 2 wk. PBZ reached a median (range) peak concentration (Cmax) of 9.42 (2.74-11.5) g/ml at a mean (range) time (Tmax) of 6.00 (4.00 to >12.00) h, and the median (range) elimination half-life (T1/2) was 6.07 (3.95-6.49) h. Phenylbutazone pharmacokinetic parameters for black rhinoceros in this study were similar to domestic horses. Meloxicam reached a median (range) Cmax of 0.576 (0.357-0.655) µg/ml at a median (range) time (Tmax) of 6.00 (4.00-12.00) h; the median (range) T1/2 of MEL was 14.0 (12.4-17.9) h. These results demonstrate that once-daily administration of MEL at 0.3 mg/kg resulted in a serum concentration of greater than 0.200 µg/ml from 2 to 24 h in four animals, which is within the analgesic range (0.200-0.400 µg/ml) for this drug in other species postulated by other studies. A single dose of firocoxib (0.1 mg/kg) reached a median (range) peak concentration (Cmax) of 15.7 (9.65-17.3) ng/ml at a median (range) Tmax of 4.00 (4.00-6.00) h. The median (range) elimination T1/2 of FIR was 4.96 (4.47-6.51) h, which is faster than in the horse. The data suggest that extrapolation from equine FIR dosage recommendations is inappropriate for black rhinoceros.

Skin derived branched‐chain fatty acids in fetal horse gut

AbstractBranched‐chain fatty acids (BCFAs) are mostly saturated fatty acids with a methyl branch at the penultimate or antepenultimate position to the CH3 end. Very‐long‐chain BCFAs (C ≥ 20) are uniquely found in surface lipids. Human and California sea lion (Zalophus californianus) are the only two species that possess vernix at birth, and vernix particles carry loads of BCFA to the gut, potentially influencing the establishment of the first microbiota. Horse (Equus caballus) contains high levels of BCFA in its surface lipids, and the current study aims to investigate if BCFA are components of a neonatal foal's gut. Electron ionization tandem mass spectrometry was used to distinguish iso‐ and anteiso‐form of BCFA from straight‐chain fatty acids. Abundant very‐long‐chain iso‐BCFA, mainly even‐numbered iso‐20:0, iso‐22:0, iso‐24:0, and iso‐26:0 were found in horse meconium but not in their manure collected a few months later. There are little differences in BCFA types and concentrations between foal manure and adult manure. Moderate to high levels of very‐long‐chain anteiso‐BCFA were also found. Comparisons of horse meconium BCFA to horse skin cholesterol ester BCFA content and to meconium from human and sea lion suggest its skin derived origin. The study expands our knowledge on the gut nutritional environment of a newborn horse, and further study is needed to establish the relationship between gut BCFA and microbiota composition in the first few hours of life.Practical Applications: Branched‐chain fatty acids (BCFA) are bioactive compounds found in vernix caseosa, the lipid‐laden material covering the surface of a newborn baby. BCFA also reaches high concentrations from the third trimester of gestation until birth. However, the exact functionality and mechanisms of BCFA in the surface and gut of a fetus remain unclear. The current study aims to clarify the lipid conditions in the gut of newborn foals and to identify the associations between BCFA in the gut and on the skin at a critical point when the horse's microbiota establishes itself. The findings of the current study lay a path for studying the physiological functions of BCFA in horse models, potentially accelerating research related to BCFA.

Spontaneous eye blinks in horses (Equus caballus) are modulated by attention

Spontaneous eye blinks are brief closures of both eyelids. The spontaneous eye blink rate (SEBR) exceeds physiological corneal needs and is modulated by emotions and cognitive states, including vigilance and attention, in humans. In several animal species, the SEBR is modulated by stress and antipredator vigilance, which may limit the loss of visual information due to spontaneous eye closing. Here, we investigated whether the SEBR is modulated by attention in the domestic horse (Equus caballus). Our data supported previous studies indicating a tonic SEBR specific to each individual. We also found that, superimposed on a tonic SEBR, phasic changes were induced by cognitive processing. Attention downmodulated the SEBR, with the magnitude of blink inhibition proportional to the degree of attentional selectivity. On the other hand, reward anticipation upregulated the SEBR. Our data also suggested that horses possess the cognitive property of object permanence: they understand that an object that is no longer in their visual field has not ceased to exist. In conclusion, our results suggested that spontaneous eye blinks in horses are modulated by attentional cognitive processing.

Numerical discrimination in domestic horses: a spontaneous binary choice test

Numerical discrimination in domestic horses: a spontaneous binary choice test

Stress Responses in Horses Housed in Different Stable Designs during Summer in a Tropical Savanna Climate.

Single-confinement housing can pose welfare risks to domestic horses. This study investigated horses' stress responses when confined to single stalls in different stable designs in a tropical savanna region to address a gap in the literature. In total, 23 horses were assigned to a stable with a central corridor and solid external walls (A) (N = 8), a stable with one side corridor and solid external walls (B) (N = 6), or a stable with a central corridor and no solid external walls (C) (N = 9). Air velocity, relative humidity, air temperature, and noxious gases were measured inside the stables, and the heart rate and HRV of the horses were also determined. The relative humidity was lower in stable C than in stable A (p < 0.05), while the air temperature was higher in stable C than in stable B (p < 0.05) during the day. The airflow and ammonia levels were higher in stable C than in stables B and A (p < 0.01-0.0001). Overall, horses' HRV in stable A was lower than in those in stables B and C (p < 0.05-0.01). Horses in stable A tended to experience more stress than those in other stables.

Horses look longer at skilled humans than unskilled ones despite similar outcomes in an object manipulation task

Evaluating others based on skillfulness and prosociality is an important ability in choosing a cooperative partner. Such abilities have been studied in nonhuman species such as primates and dogs; however, few studies have examined whether horses could evaluate humans based on their skillfulness. Here, we investigated whether horses (Equus caballus) could evaluate humans based on their skillfulness in a situation related to their own interests (food). We showed horses a pair of experimenters, one that could open the lid of a container (skilled actor) and another that could not open the lid of the container (unskilled actor). The unskilled actor ‘accidentally’ dropped the container during the demonstration phase, causing the lid to open, allowing him to remove the object and thus achieve the same outcome as the skilled actor. The experimental trials involved two conditions, one in which the container had food inside, and one in which it was empty. This was because we thought the horses would have an expectation that the skilled actor would give them food after opening the container, so we predicted that horses would look longer at the skilled actor than the unskilled actor only in the food condition. We measured the gaze duration of horses toward each experimenter. Horses looked longer at the skilled actor overall and looked at the two actors longer in the food condition than in the non-food condition, and there was no interaction between role and condition. Post-hoc tests showed that the horses looked at the skilled actor longer than the unskilled actor in both conditions. They also looked at the skilled actor for longer in the food condition compared with the no-food condition. These results suggest that the horses were able to visually discriminate between humans based on their skillfulness.

Jaguar predation on domestic horses in the dry forest of northwestern Costa Rica

AbstractDepredation of domestic horses (Equus caballus) by jaguars (Panthera onca) is an example of human–wildlife conflict that has not received much attention. We monitored spatio‐temporal activity and distribution of horses in a 2.64‐km2 fenced area in the dry forest of northwestern Costa Rica in response to 16 jaguar killings of horses during January‐November 2017. We monitored 4 horses (2 males, 2 females) equipped with global positioning system transmitters from February‐September 2018 to identify daily and seasonal patterns of use of cover types and a water source by horses. We then compared these results to the previous locations where jaguars killed horses to identify the circumstances under which horses seemed more vulnerable to jaguar predation. Based on 1,693 locations, horses spent most time in grassland (92%) rather than forest and edge vegetation (8%) and used a core area of 0.74 km2 (kernel density estimation) to 0.86 km2 (minimum convex polygon). Of 16 horse predation events by jaguars, 9 events (56%) occurred in grasslands, 4 in forested areas (25%), and 3 in the forest edge (19%), indicating predation events occurred disproportionately from expected counts based on horse use of vegetation. The predation sites were characterized by a higher proportion of edge and a lower proportion of forest compared to a random points. We suggest that when horses explored areas near the edge of forested areas, the chances of being preyed on by jaguars increased.