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Topic:Physiology
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.
Physiological and behavioural effects of continuous remifentanil-xylazine administration in donkeys. Remifentanil and xylazine are used as continuous infusions to facilitate standing surgery in horses. Their use for this purpose has not been reported in donkeys. Objective: To evaluate the behavioural, sedative, and cardiorespiratory effects of continuous intravenous infusion of remifentanil and xylazine in donkeys. Methods: Non-blinded in vivo experiments. Methods: Ten donkeys were sedated with an intravenous bolus of xylazine (0.8 mg/kg). After 3 min, continuous infusions of xylazine (0.65 mg/kg/h) and remifentanil (6 μg/kg/h) were administered for 60 min. Cardiorespiratory physio...
Child horse harmony in motion: a preliminary study to explore heart rate synchronization in equine assisted therapy for neurotypical and ADHD children. 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...
Salivary cortisol concentration in western performance horses and riders: Associations with performance. 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...
Cardiac-Metabolic Coupling Revealed by Lipid and Energy Metabolomics Determines 80 km Endurance Performance in Yili Horses. This study aimed to investigate the regulatory mechanisms underlying the relationship between cardiac structure and function and plasma metabolic characteristics in Yili horses participating in an 80-km endurance, by integrating echocardiography, lipidomics, and energy metabolomics analyses. Twenty four competing Yili horses were selected and divided based on competition outcomes: Pre-Completion Group: PCG ( = 6); Post-Completion Group: PoCG ( = 6); Overtime Completion Group: OCG ( = 6); and Non-Completion Group: NCG ( = 6). Cardiac structural and functional parameters were assessed via echoca...
Proof of concept of a wearable IoT-based system for monitoring respiratory rate and surface temperature in horses. 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...
Chronic State and Relationship to Humans Influence How Horses Decode Emotions in Human Voices: A Brain and Behavior Study. 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...
Heart rate and heart rate variability responses during three exercise tests and recovery in horses participating in the Fédération Équestre Internationale Eventing World Challenge. 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...
Locomotory Profile, Heart Rate Variability, and Blood Parameters Reveal Adaptive Responses in Endurance Horses Trained on Deep Sand. 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...
Editorial: Advances in the application of technology for monitoring horse welfare and health. 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.
Assessment of olfactory sensitivity in horses using positively conditioned scent. 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...
What if Horses Were Humans? Comparing Rein Tension and Bit Pressures to Human Pressure Pain Thresholds. Bit pressure and rein tension-induced mouth pain in horses have recently become a significant welfare concern, fueling debates within the equestrian community and beyond. Evidence indicates that bits can cause pain-related behaviors and even oral lesions. Although studying pressure-induced pain in animals is challenging, the similarities in the physiology of pain processing (nociception) across mammals suggest that it is reasonable to assume that pain perception in humans and horses is principally comparable. Therefore, we compared human pressure pain detection thresholds (PPDTs) to reported r...
Relationship between weight-carrying capacity and performance in a standardized treadmill exercise test in horses. Weight-carrying capacity is important in riding horses both for performance and welfare, yet there is no standardized method to estimate individual horses' weight-carrying capacity. This study investigated the correlation between the physiological response during a (i) standardized incremental exercise test (SET) on a treadmill and a (ii) ridden incremental weight-carrying exercise test (WET). Sixteen horses (15 ± 3 years) performed both tests, including four steps with increased speed or weight load, respectively. Body weight ratio (BWR) in the WET was 20%, 25%, 30%, and 35% in each st...
Single-Cell Transcriptomic Profiling of Longissimus Dorsi and Biceps Femoris Muscles in Kazakh Horses Reveals Cellular Heterogeneity and Myogenic Regulation. 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...
Physiological and Behavioral Responses of Stabled Horses (Equus caballus) to Three Types of Environmental Enrichment. 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...
The Influence of Horse Age, High-Pressure Technique and Various Heat Treatment Methods on the Quality of Horse Meat. The aim of this study was to demonstrate the effect of horse age, high-pressure cooking, and various heat-treatment methods on the quality of horse meat. The research material consisted of samples of the longissimus thoracis muscle obtained from 14 horse carcasses from two age groups. Samples of the muscle were subjected to traditional cooking (TC), sous-vide cooking (S-V), high-pressure cooking (HHP), HHP + TC, and HHP + S-V. The chemical composition, physicochemical properties, color parameters, pigment levels, texture parameters, and sensory properties of the meat were determined. Exposing...
Preliminary insights on the daily rhythm of CRP and IL-6 in athletic horses. Homeostasis and inflammation are two opposing physiological processes that are driven by the circadian clock. Objective: The study aim was to investigate the biological rhythm of the C-reactive protein (CRP) and Interleukin-6 (IL-6) in horses. Methods: Eight clinically healthy Italian saddle gelding horses, housed in individual boxes and subjected to a natural 12/12 L/D cycle, were enrolled. Blood samples were performed every 4 hours over a 48-hour period. Results: A positive correlation was found between CRP and IL-6 on both days of monitoring. Both parameters showed a daily rhythm; CRP acrop...
Intrinsic characteristics of donkeys that affect drug treatment. Donkeys have contributed to the development and livelihoods of humans for almost 7,000 years. They have been used for traction and transportation, kept as pets, utilized in animal-assisted therapies, or farmed as food-producing animals. Over the past two decades, significant progress has been made in bridging the knowledge gap in veterinary medicine between donkeys and horses. Veterinary practitioners are now more aware that donkeys have important behavioral, anatomical, and physiological characteristics that distinguish them from horses. These peculiarities should be considered when treating ...
Efficacy and welfare effects of different forms of physical restraint for upper airway endoscopy of horses. Physical restraint of horses for veterinary procedures is necessary to allow completion of tasks effectively and without injury to patient or personnel. Objective: To compare physiological effects and behavioural responses to four commonly used restraint techniques for upper respiratory tract (URT) endoscopy in unsedated horses. Methods: Blocked and randomised interventional study. Methods: Twelve university owned teaching horses were blocked into groups of four and randomly allocated to one of four restraint methods (nose twitch, ear hold, Stableizer® and nil restraint) for URT endoscopy. Ho...
Technologies for equine welfare and performance monitoring under field conditions – Where do we stand? The need for comprehensive equine welfare assessments has become particularly evident amid ongoing debates about the social licence to operate in equestrian sports. During exercise, multiple physiological systems, principally the cardiovascular, respiratory, muscular, thermoregulatory, endocrine, and locomotory systems, undergo complex adaptations. To monitor and determine equine welfare, an approach that focuses on the quantitative monitoring of both physiological and psychological parameters to determine and understand the impact of equestrian sports on horses is essential. Existing and emer...
Cortisol and heart rate response of mares during the in-hand breeding procedure with and without restraint. In-hand breeding involving restraint methods is likely the most common practice in the horse breeding industry worldwide. However, welfare issues that arise from such management have not been investigated in detail. Objective: (1) To investigate whether the mares show increased stress responses during in-hand breeding using (a) a lip twitch and (b) hobbles. (2) To evaluate if the use of restraint methods influences the mare's expression of oestrous behaviour. Methods: Intra-individual cross-over design. Methods: Six Franches-Montagnes stallions and 10 warmblood mares were used in these experim...
Ionic composition of gastric reflux and small intestinal fluid in horses: implications for fluid replacement. Small intestinal (SI) distension and gastric reflux (GR) are common in horses with mechanical and functional ileus. Removal of GR results in fluid/ion losses. Objective: 1) Determine the capacity of healthy SI; 2) measure ion concentrations in normal SI fluid, GR, or fluid from SI undergoing resection. The authors hypothesized that Na and Cl concentrations would be lower and higher, respectively, in GR as compared to SI fluid from healthy horses, while there would be little difference in K concentration. Methods: Observational study: two to 15 meters of SI from 15 horses were distended with wa...
Long-Term Changes of Physiological Reactions in Young Lipizzan Stallions During Exercise Testing. The aim of the study was to determine the fluctuations of selected physiological parameters in young Lipizzan stallions ( = 10) during the initial phase of their training as indicators of adaptation to a graded exercise load and stress exposure. For this purpose, four exercise tests (ExT) with lunging were carried out over a period of one year. Physiological parameters (gait speed, heart and respiratory rate (HR and RR), rectal and body surface temperature (RT and BST), and cortisol and lactate concentration (CORT and LAC)) were measured before and after training. In all ExT, gait speeds incre...
Differential Metabolomics and Cardiac Function in Trained vs. Untrained Yili Performance Horses. This study aimed to investigate the effects of training on cardiac structure and function, as well as plasma metabolite profiles in horses, in order to uncover the molecular regulatory mechanisms and cardiac remodeling under long-term exercise. We hypothesize that long-term standardized training induces physiological cardiac remodeling and differential metabolomic changes in Yili horses, which correlate with improved athletic performance. The study focuses on physiological exercise-induced cardiac remodeling, characterized by increased left ventricular wall thickness and chamber size. A total ...
Horse vision through two lenses: Tinbergen’s Four Questions and the Five Domains. To improve human-horse interactions and reduce the risk of injury, it is essential to adopt an equi-centric perspective that prioritizes how horses perceive their environment. This review focuses on the equine visual system, both because it is the most studied of the horse's senses and because misunderstandings about how horses see can lead to unsafe or unsustainable handling. By applying two complementary frameworks, namely Tinbergen's Four Questions and the Five Domains model, we examine equine vision from both a biological and a welfare-oriented perspective. We explore the anatomical and fu...
Melatonin receptors and thyroid stimulating hormone in the equine pars tuberalis: Potential modulators of seasonal reproduction in the mare. The mechanism by which photoperiod influences the hypothalamic-pituitary-gonadal (HPG) axis and regulates seasonal reproduction in horses has yet to be fully elucidated. The hypophyseal pars tuberalis (PT) has been indicated as a critical site for the transduction of melatonin signals through melatonin-responsive, PT-specific cells that produce thyroid-stimulating hormone (TSH) in many mammalian species. However, this has yet to be investigated in horses. The objective of this study was to explore the interaction of melatonin and thyroid-stimulating hormone in the equine HPG axis. Pituitaries ...
Cannabinoid Receptors in the Horse Lateral Nucleus of the Amygdala: A Potential Target for Ameliorating Pain Perception, Stress and Anxiety in Horses. The amygdala is composed of several nuclei, including the lateral nucleus which is the main receiving area for the input from cortical and subcortical brain regions. It mediates fear, anxiety, stress, and pain across species. Evidence suggests that the endocannabinoid system may be a promising target for modulating these processes. Cannabinoid and cannabinoid-related receptors have been identified in the amygdala of rodents, carnivores, and humans, but not in horses. This study aimed to investigate the gene expression of cannabinoid receptors 1 (CB1R) and 2 (CB2R), transient receptor potential...
Gestation-Stage Related Changes in the IGF System Components in the Equine Placenta. The insulin-like growth factor (IGF) system regulates implantation, placental development, and angiogenesis in eutherian mammals. However, little is known about the changes in this system in equine placenta (chorioallantois; CA) and the endometrium (EN) during pregnancy, or the relationship to vascular endothelial growth factor () expression. The current study investigated the expression of the IGF system components, namely the ligands ( and ), their receptors (, , and ), and their binding proteins ( and s) in equine CA at 45 days, 4, 6, 10, and 11 months of gestational age (GA) and immediatel...
Sedative effects of detomidine and midazolam combination in horses. The combination of detomidine and midazolam may provide safer sedation with muscle-relaxant effects, which are particularly necessary during standing procedures. Unassigned: Thus, the objective of this study was to evaluate the sedative and muscle-relaxant effects of the detomidine/midazolam combination in horses through a pharmacodynamic study. Unassigned: Five horses were used and subjected to four experimental protocols: 15 µg/kg of detomidine (D15); a combination of detomidine (15 µg/kg) with 25 µg/kg (DM25), 50 µg/kg (DM50), or 75 µg/kg (DM75) of midazolam administered intravenously....
Brain-derived neurotrophic factor and neurotrophic tyrosine receptor kinase-2 in stallion testes: insights into seasonal changes and potential roles in spermatogenesis. 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...
Colombian Criollo horses’ trot, trocha, and gallop are submaximal oxygen consumption gaits with unique locomotory-respiratory coupling. Colombian Criollo horses are bred for their smooth gaits that emphasize full collection and rapid footfall. The physiological demands of these gaits remain unknown. Our objective was to determine if oxygen consumption, ventilation, locomotor-respiratory coupling, and running economy differed between the trot or trocha and the gallop. Unassigned: 7 competition horses completed a controlled design standardized field test between January 10 and 20, 2025. Horses wore a cardiotachometer and ergospirometer to measure heart rate, oxygen consumption, and ventilation at the trot or trocha and the gallo...
