The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
Olitsky PK, Long PH.The virus of vesicular stomatitis is not readily killed by formalin. This chemical is one of a group which coagulates the proteins of the medium in which the virus is usually contained. It has already been found(7) that other reagents of the protein-coagulating group are not actively virucidal) and the effect of formalin in this instance is therefore characteristic of the group. The so called formalinized vaccines which give rise to immunity can be shown to have done so because of the presence of living virus. A single injection of such so called "vaccine," or of other material containing livi...
Abramson HA.1. The cataphoretic velocity of blood platelets (horse) in plasma has been found to be between 40 and 51 micro per sec. per volt per cm. The mean velocity obtained from five horses is . 45 micro per sec. per volt per cm. 2. The cataphoretic velocity of polymorphonuclear leucocytes in similar specimens is practically identical with that of the platelets. This is noteworthy because of the fact that lymphocytes and red cells have different speeds. 3. With spontaneous agglutination of platelets, white cells and red cells, there is no change in the cataphoretic velocity incidental to aggregation. 4...
Friedlander M, Sobotka H, Banzhaf EJ.The precipitin indices for a number of monovalent and polyvalent antipneumococcus sera were determined under known conditions, and found to vary as did the number of protective units. The ratio precipitin index/protective units in monovalent sera was found to lie between 2.8 and 4.8 for Type I and to be about ten times greater for Type III. Lower values were found in polyvalent horses and when mixing heterologous monovalent sera with each other. The influence of the duration of treatment upon the quotient was studied. Several refined and concentrated preparations showed a relative increase in ...
Reimann HA.It is conceivable that a change from the virulent, non-phagocytable S form of Pneumococcus to the avirulent phagocytable R form may take place in pneumococcus disease, but the experiments here reported do not settle the question whether or not this is an important factor in determining the outcome in natural infection. It has been shown experimentally that the degradation from the S form to the R form actually does take place in cultures of Pneumococcus growing in agar subcutaneously embedded in guinea pigs, in agar enclosed in vials subcutaneously embedded in rabbits, and spontaneously in the...
Jungeblut CW.1. A flocculation reaction has been described which occurs between alcoholic extracts of pneumococci and antipneumococcus serum. 2. The reaction appears to be species-specific. It is not strictly type-specific, as slight or moderate cross-reactions occurred between Type I serums and Type II and Type III extracts. 3. The flocculating power of the serum from five horses undergoing immunization with pneumococcus, Type I, did not develop to any extent before the end of the 4th or 5th month. 4. In the case of two of these horses in which it was possible to carry out parallel tests on a larger numbe...
Gibson RB, Banzhaf EJ.Gravimetric determinations were recorded for the total and several individual proteins (in the sodium oxalate plasma) fractioned with ammonium sulphate and sodium chloride. At precipitation, the plasma salt mixture had been diluted to a final volume of ten times the amount of plasma employed. Coagulations were on aliquot portions of filtrates, and the individual protein constituents (except serumalbumin) were calculated by difference. The eleven horses had been subjected to simultaneous immunization against diphtheria and tetanus toxins, each horse being subsequently continued on the toxin to ...
Hubbert WR.1. Better results in the production of diphtheria antitoxin can be obtained with greater experience in the selection of the most suitable type of horses to be used. Young animals are usually to be preferred. Over one-half of all such horses can be made to yield 300-unit serum, while a third will yield (5)oo-unit serum. 2. High-test horses require a shorter time to immunize and will yield a potent serum for a longer period than will low-test horses. 3. The period of usefulness of an antitoxin horse is short, and on an average endures only a few months. 4. A horse having attained a maximal antit...
Hiss PH, Atkinson JP.THE RESULTS OF THE FOREGOING EXPERIMENTS MAY BE BRIEFLY SUMMARIZED AS FOLLOWS: The amount of antitoxic substance obtained by precipitation with magnesium sulphate from the blood-serum of the horse corresponds, as nearly as can be determined by the use of test guinea-pigs, in full to the protective power of the serum from which it is obtained, i. e. the precipitate from 1 cc. of serum will protect against the same amount of toxin as 1 cc. of the serum itself. Equal amounts of the precipitates by magnesium sulphate from immunized and non-immunized horses act differently toward toxin; i. e. the p...
Atkinson JP.1. The globulins of both normal and diphtheria antitoxic serum exhibit chemically toward reagents the same reactions, being precipitated by magnesium sulphate and split up into fractions in precisely the same way. 2. All of the diphtheric antitoxic power of both normal and immunized serum is always carried by the globulin and its fractional precipitates. 3. During the fractional precipitation of the serum globulin of horses immunized from diphtheria toxin and horses not immunized from diphtheria toxin, some of the globulin is lost, likewise at the same time some of the antitoxic power of the g...
This article provides an overview of initial assessment and management of common emergency presentations in donkeys and mules. The principles are similar to those in horses (and ponies), but clinicians must be aware of differences in recognition of signs of pain/disease, approach to handling, pharmacology of some drugs, and subtle differences in the physiology and local anatomy in donkeys and mules. The epidemiology of common disease presentations will vary between pet/companion or working/farmed donkeys and mules. Regular dental checks, deworming, vaccination, and monitoring of behavior and q...
Mares were inseminated with motile spermatozoa suspended in 30-150 microliters Tyrode's medium directly onto the uterotubal papilla at the anterior tip of the uterine horn, ipsilateral to the ovary containing a dominant preovulatory follicle of > or = 35 mm in diameter, by means of a fine gamete intrafallopian transfer (GIFT) catheter passed through the working channel of a strobed light videoendoscope. Insemination of 10, 8, 25, 14, 11 and 10 mares with, respectively, 10.0, 5.0, 1.0, 0.5, 0.1 or 0.001 x 10(6) motile spermatozoa resulted in conception rates of, respectively, 60, 75, 64, 29,...
Wang J, Li Z, Li L, Wang R, Ma S, Su Y, Shan D, Huang Q.Kazakh horses are renowned for their endurance and adaptability, with distinct muscle groups such as the longissimus dorsi (LD) and biceps femoris (BF) muscles serving specialized functions. However, the molecular mechanisms underlying the functional specialization of these muscles in Kazakh horses remain poorly understood. This study aims to address this gap by utilizing single-cell RNA sequencing (scRNA-seq) to investigate the transcriptomic differences between these muscle groups, with a focus on understanding their molecular adaptations. Our analysis revealed that the BF muscle, specialize...
Brauns M, Ali A, Berger J, McLean A.Small stalls and regulated feedings restrict horses' natural foraging and locomotion, increasing risks to welfare. Environmental enrichment may promote more naturalistic behavioral time budgets, yet little is known about how enrichment type or timing affects physiology and behavior. This study examined nine stabled Quarter Horses provided with hay feeders, activity balls, or mirrors across randomized trials. Each trial included 30 min observations, four times per day, with enrichment removed between sessions and 5-day washouts between trials. Nightwatch Smart Halters™ recorded heart and resp...
Wonghanchao T, Sanigavatee K, Pongnarudech P, Suchairat T, Jitsopin S, Wanichayanon B, Rattanakarn D, Jantakanangkoon P, Jaraswutiwong T, Kalanuson N....Horses competing in eventing competitions encounter significant challenges that increase their risk of severe injuries and metabolic disorders. Numerous studies have focused on the risk of such injuries and disorders during the cross-country segment. While one study has examined autonomic responses during this segment, research on these responses across all three phases of competition, particularly during one-day events, is still limited. The objective of this study was to analyse the autonomic responses of horses by measuring heart rate (HR) and heart rate variability (HRV) during three exerc...
Dalla Costa E, Bovo M.Flowchart illustrating interdisciplinary collaboration in animal research. A horse symbolizes the focus, with pathways connecting physiology, behavior, and environment to decision-making and regulatory indications. Data analysis, system understanding, and data interpretation lead to feedback and warning. Visual elements include sun, clouds, a light bulb, gears, and a graph.
Wnuk E, Janicka W, Stachurska A, Owerczuk R, Łuszczyński J.Differences in the ranges and capacities of sensory modalities cause horses to perceive their surroundings differently than humans. To date, the horses' sense of smell has been studied mainly regarding social and reproductive behaviour. The role of olfaction in horse management and use also seems to be of utmost importance. The aim of this study was to determine the response to a scent of different intensities by horses of different sexes and types (warmblood horses vs ponies). The study involved 21 adult mares and geldings, of which 15 subjects learned how to complete the required task and we...
Farias BJP, Furtado DA, Barbosa do Nascimento JW, Neto JPL, de Morais FTL, Santos TLS, Vasconcelos AS, Silva RC, Alves JIP, Mcmanus C, Silveira RMF....This study presents the development and proof of concept of a wearable monitoring system designed to measure respiratory rate (RR) and coat surface temperature (CST) in horses. The device integrates an embedded system based on an ESP-32 microcontroller equipped with sensors for RR (strain gauge) and CST (DS18B20) Data are transmitted in real time via Wi-Fi and stored locally on SD cards. The system was validated against conventional manual methods under field conditions. Agreement between methods was evaluated using Intraclass Correlation Coefficients (ICC) and Bland-Altman plots. Results show...
d'Ingeo S, Siniscalchi M, Quaranta A, Cousillas H, Hausberger M.Current research on acoustic encoding of emotional content suggests that there are universal cues, allowing for decoding within and across taxa. This is particularly important for human-animal relationships, wherein domestic animals are supposed to be particularly efficient in decoding human emotions. Here we investigated whether the decoding of the emotional content in human voices shared universal acoustic properties, or whether it could be influenced by experience. Emotional human voices were presented to two populations of horses, in which behavioral, cardiac, and brain responses were meas...
Pennington MV, Zoller JL, White-Springer SH, Harlin JF, Huseman CJ, Leatherwood JL, O'Reilly CL.Competition stress is a common factor influencing the success of performing athletes. However, few studies have quantified the physiological stress responses in horses and riders surrounding an equestrian event. Objective: The objectives of the current study were to determine salivary cortisol concentrations (SCC) as an indicator of stress in fifteen horse and rider pairs competing in western stock horse events and to investigate the relationship between SCC and performance. Methods: Subjects included male and female Quarter horses aged 3-15 years and equestrians aged 18-22 years. Salivary sam...
Training on deep sand is commonly employed in endurance horses, but its physiological adaptation remains poorly characterized. This study aimed to characterize locomotor adaptations during a 7 km controlled-speed canter on deep sand in eighteen endurance horses, to identify heart rate variability (HRV) components, and to investigate changes in hematological variables before and after exercise. Stride frequency (SF) and stride length (SL), HRV, and hematological profiles were recorded during exercise and recovery with a fitness tracker. Associations between maximum speed and locomotor parameter...
Brito G, Damián JP, Trigo P, Ruprechter G.The Raid Hípico Uruguayo (RHU) is the oldest equestrian endurance sport in Uruguay. A high percentage of horses fail to complete RHU rides. Therefore, the aim of this study was to investigate whether weather conditions (comfort index [CI]), horse experience, and ride distance affect horse performance (finishing ride [FR] or nonfinishing ride [NFR]) in the RHU. An additional objective was to determine whether finishing the ride affects the hematological and biochemical parameters of the horses. This study involved 17 RHU rides over distances of 60-90 km and 284 horses. Blood samples were tak...
Tripon MA, Manolăchescu D, Papuc I, Daradics Z, Crecan CM.Emotional contagion between horses and humans is a key aspect of their interaction, influencing welfare, training, and therapy, yet current methods for measuring this phenomenon lack standardization and consistency. Objective: The aim of this study was to verify what methods are used to assess emotional contagion in horse-human interactions, and what outcomes have been reported. Methods: A systematic search of Google Scholar, Web of Science, Scopus, PubMed, and Science Direct was conducted up to March 2024. Peer-reviewed studies assessing emotional transfer through behavioral and/or physiologi...
Briefer-Freymond S, Dalla Costa E, Jolivald A, Bruckmaier RM, Atallah E, Giorgia Riva M, Ijichi C.Personality affects both experience and expression of pain and the welfare impact of castration on horses is poorly understood. Therefore, the current study observed 19 horses to determine: the welfare impact of standard castration on horses; whether individuals consistently vary in their behavioural and emotional responses to pain; the influence of personality on behavioural and physiological responses to pain; whether Horse Grimace Scale (HGS) indicates how individuals feel about painful experiences. Eye temperature (IRT), salivary cortisol, HGS and a pain ethogram were measured at intervals...
Bao Y, Wang T, Adina W, Yao R, Chu H, Yao X, Meng J, Wang J, Ren W, Zeng Y.This study aimed to investigate how different training outcomes affect the gut microbiota composition in racehorses. Twenty-six Yili horses underwent a 9-month conditioning training regimen under uniform husbandry and management conditions. Post-training, the horses were divided into an excellence group (D. Y group) and a general group (D. P group) based on their athletic performance, with the top 10 performers constituting the D. Y group and the bottom 10 the D. P group. Cardiac morphology and function were quantitatively assessed via echocardiography, and metagenomic sequencing was performed...
Sharma M, Singh A, Kumar V, Olla N, Arora R, Sharma R, Mohan NH, Ahlawat S.The genus Equus, encompassing horses, donkeys, and extinct relatives, has evolved over approximately 55 million years from small, multi-toed ancestors to the modern horse. Selective breeding has produced over 600 distinct horse breeds optimized for diverse traits such as size, conformation, performance, and adaptability. In the past two decades, rapid advances in equine genomics have significantly deepened our understanding of the molecular basis of these traits. The integration of high-throughput sequencing, genome-wide association studies (GWAS), and single-nucleotide polymorphism (SNP) geno...
Ake AS, Akinniyi OO.Clinical assessment of parameters that give indications of the health status and fitness of horses are very important in equine practice. The study aimed to compare the resting body temperatures at different anatomical sites and resting pulse rates of athletic and non-athletic horses. Eighteen horses were used for the study, comprising ten athletic and eight non-athletic horses. Measurements of environmental parameters, rectal temperature (RT), body surface temperature (BST) and pulse rate were recorded between 9 and 11 am twice with one week interval at the Ibadan Polo Club, Eleyele, Ibadan, ...
Crossland WL, Aviles-Rosa EO, Perry EB, Crowell C, Webberson E, Brown J, Fassbender J.Our objective was to evaluate the effect of transdermal melatonin on physiological stress biomarkers in horses, with some subjected to transport stress. Sixteen horses were assigned to a 2 × 2 factorial design assessing treatment (melatonin vs. no melatonin) and transport status (transported vs. non-transported), creating four groups: Control (CON), Transport only (TRS), Melatonin only (MEL), and Melatonin plus Transport (MELTRS). Horses in melatonin groups received 24 mg/day transdermally for 21 days and transported groups underwent a 3-hour trailer ride on day 21. Day 21 blood samples were ...
Jones CJP, Aplin JD, Wilsher S.There is little information on non-ciliated secretory cell numbers in the equine oviduct isthmus over the course of the estrous cycle and the effect, if any, of insemination. Lectin histochemistry was used on a series of 13 oviducts taken at different stages of the estrous cycle, with and without insemination, to monitor glycosylation changes and the distribution of secretory cells characterised by a prominent cytoplasmic accumulation of glycoconjugates. There appeared to be an increase in secretory cells expressing a wide range of glycans in all specimens at estrus. One day after ovulation, o...
D'el Rey Dantas FT, Forni G, Hallowell G, Castagnetti C, Menchetti L, Romito G, Lanci A, Mariella J, Freccero F.Bodyweight, age and breed influence the echocardiographic assessment of foals. There are no echocardiographic studies in Standardbred neonatal foals. Objective: To describe echocardiographic values for selected variables, evaluate intra- and inter-observer variability and assess cardiac changes in the first 5 days of life in healthy Standardbred neonatal foals. Methods: Prospective observational study. Methods: Fifty-six healthy Standardbred neonatal foals were examined by transthoracic echocardiography using standard right parasternal and subcostal views at three time points: in the first 4...
Hämäläinen MJ, Brotherus IL, Wigren HM, Kaimio TE, Suomala H, Olbricht AM, Hänninen LT, Mykkänen AK.Reduced rapid-eye-movement (REM) sleep is associated with impaired learning in many species. We developed a reversal learning test (RLT) suitable for field conditions to explore this association in 16 healthy horses. Nocturnal REM-like sleep behavior was recorded five times for 48 h over a six-week period. The horses performed a target training task followed by an RLT using two objects. When the horses reached a predefined frequency of touching the object, the spatial location was reversed. Mean test parameters were statistically analysed using GENLIN models, longitudinal continuous variables...
Andrews KE, Sibthorpe PEM, Fitzgerald DM, de Laat MA.Equine insulin dysregulation (ID) is a common condition that predisposes to hyperinsulinaemia-associated laminitis. Improved pathophysiological understanding would enable better management of ID and reduce the risk of laminitis. The incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), augment the insulin response to dietary glucose and GLP-1 has been implicated in the pathophysiology of ID. However, their temporal variation in response to a low-energy diet has not been reported. This study determined the variation in GLP-1, GIP and insulin ...
Shroff K, Underwood C, Stefanovski D, Hopster K, Slack J.To determine transthoracic impedance (TTI) in adult horses using an exponential biphasic defibrillator and investigate patient and technique factors influencing TTI. Unassigned: A randomized crossover design with 2 phases was used. Phase 1: TTI was measured in dorsal and lateral recumbency, with and without manual pressure on the electrodes in deceased horses immediately following euthanasia. Phase 2: TTI was measured in dorsal recumbency during inspiration and expiration using anesthetized live horses sourced from 2 terminal studies. Mixed-effects linear regression modeling was performed to a...
Freitas Silva D, Passagli Barbosa D, de Paula Rodrigues J, Robaina Sancler-Silva YF, Saules Ignácio F, Lucena Fredou M, Segabinazzi L, Monteiro GA.Doppler ultrasonography is a valuable tool for monitoring testicular hemodynamics, offering improved diagnostic insight and supporting treatment monitoring. However, its use in equine andrology remains limited due to a scarcity of published data and reference values. Therefore, this study aimed to characterize the testicular arterial blood flow patterns in clinically normal stallions and stallions with 180° spermatic cord torsion. Spectral Doppler ultrasonography was performed on both testes of 48 Mangalarga Marchador stallions. Thirty stallions with normal testes were divided into three age ...
Ver Goltz L, Gomes SP, Schimming BC, Abdala FCM, Miglino MA, de Castro Sasahara TH.The equine ovary exhibits unique structural and developmental features that distinguish it from those of other domestic species, including the presence of an ovulation fossa and an inversion of cortical and medullary layers. This study aimed to investigate the morphostructural development of the equine fetal ovary, with particular emphasis on the formation of the ovulation fossa. Fourteen female equine fetuses, ranging from 70 to 200 days of gestation, were collected from a commercial abattoir. Results revealed a progressive increase in ovarian volume and marked histological changes througho...
Verstraete MH, Dini P, Orellana D, Uribe-Salazar JM, Veras MM, Carneiro F, Daels P, Fernandes CB.The proper function of the placenta is essential for the health and growth of the fetus and the mother. The placenta relies on dynamic gene expression for its correct and timely development and function. Although numerous studies have identified genes vital for placental functions, equine placental molecular research has primarily focused on single placental locations, in sharp contrast with the broader approach in human studies. Here, we hypothesized that the molecular differences across different regions of the equine placenta are negligible because of its diffuse placental type with a macro...
Lefèvre RA, Barluet de Beauchesne L, Sabarros F, Briefer Freymond S, Ramseyer A, Keller M, Reby D, Fitch WT, Briefer ÉF.Understanding why the frequencies of some species' vocalizations are far above or below those predicted by body size is key for explaining the remarkable diversity of mammalian vocal behavior. Horses, among the largest terrestrial mammals, provide a clear example of such deviation: their whinnies contain a very high fundamental frequency (>1,000 Hz) in addition to a second, lower one (∼200 Hz). While the lower fundamental frequency of whinnies is readily attributed to vocal fold (laryngeal) vibrations, the biomechanical processes underlying the production of the higher one remain unknown. Us...
Helmer A, Hacohen A, Bart O.Equine-Assisted Services (EAS) encompass a range of therapeutic interventions utilizing equine interactions to achieve therapeutic goals. This study explores heart rate synchronization between horses and riders during mounted and unmounted interactions, focusing on its potential implications for emotional regulation. A total of 25 participants aged 6-12 took part in the study, which included two groups: novice riders diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) (n = 15) and experienced neurotypical riders (n = 10). Heart rate measurements were obtained using Polar Equ...
Shakeel M, Yoon M.Brain-derived neurotrophic factor (BDNF) and its receptor neurotrophic tyrosine receptor kinase-2 (NTRK2) have known important roles in the central nervous system for neurite growth, survival, and differentiation. Nevertheless, the significance of BDNF in spermatogenesis remains unclear in stallions. Therefore, the present study was designed 1) to investigate the expression of BDNF and its receptor NTRK2 and 2) the seasonal variation in the expression patterns of BDNF and NTRK2 in stallions' testes. We used testes from eight postpubertal Thoroughbred stallions collected after a field castratio...
Harbowy RM, Nielsen BD, Colbath AC, Robison CI, Buskirk DD, Logan AA.Though circular exercise is commonly used in equestrian disciplines, it may be at the detriment of horses' musculoskeletal system. To investigate the effects of circular exercise on bone and joint health, 42 lambs were randomly assigned to a non-exercised control, straight-line, small circle, or large circle exercise regime at a slow (1.3 m/s) or fast (2.0 m/s) speed for 12 wk. Blood samples were taken biweekly. Animals were humanely euthanized upon study completion, and the fused third and fourth metacarpals were collected for biomechanical testing and bone density analysis. Fast groups were ...
Canetti EFD, Gersbach-Seib A, Moore R, Schram B, Orr R.Within individual policing organisations, there are a wide variety of units and job roles. Unassigned: To profile the occupational tasks performed by Australian mounted police officers, aiming to offer conditioning insight into this unique job role. Unassigned: Thirteen fully qualified and operational mounted police officers (n = 11 females), who served in the mounted police unit for ∼3.3 (±2.3) years, participated in this observational cohort study. Participants completed a survey outlining common occupational tasks and were monitored throughout four consecutive shifts. Participants' h...
Friend MM, Nicodemus MC, Lemley CO, Cavinder CA, Prince P, Holtcamp K.Substance withdrawal presents a barrier to substance use disorder (SUD) recovery in part due to symptoms implicating neurotransmitters and their metabolites. Despite this relationship, research investigating alternative treatments such as psychotherapy incorporating equines (PIE) have primarily targeted vital signs and cortisol concentrations. Previous research has also proposed benefits of human-horse physiological coupling, but the role of neurotransmitters in the relationship between humans and horses during PIE has not yet been investigated. The purpose of this study was to characterize ne...
